Publications      | WebOfScience | Scopus | GoogleScholar | ORCID |

SCI articles


  1. Nagalingam S, Seco R, Kim S, Guenther A (2023) Heat stress strongly induces monoterpene emissions in some plants with specialized terpenoid storage structures. Agricultural and Forest Meteorology, 333: 109400 Supplement Abstract

    • Sunflower, western redcedar, and American sweetgum were exposed to heat stress.
    • Heat stress transformed the plants from negligible into high monoterpene emitters.
    • In some plants, monoterpene emissions were elevated for 1–7 days after heat stress.
    • Redcedar and sweetgum are not ideal for urban greening in heatwave-prone regions.
    Four different plant species, sunflower (Helianthus annuus), western redcedar (Thuja plicata), American sweetgum (Liquidambar styraciflua), and red ironbark (Eucalyptus sideroxylon), were enclosed in glass or Teflon chambers, exposed to different temperatures typically ranging from 30 °C to 43 °C, and their terpenoid emission rates were quantified using gas chromatography techniques. The results show that sunflower, western redcedar, and American sweetgum were not significant constitutive monoterpene emitters at 30 °C. Monoterpene emissions from western redcedar and American sweetgum remained negligibly low up to 35 °C–37 °C, however, at higher temperatures, the emissions began to increase at a much more rapid rate than predicted by current emission models. The monoterpene emissions from sunflower, western redcedar, and American sweetgum increased by an average factor of 22, 98, and 5900 for a temperature increase (ΔT) of 13 °C, 13 °C, and 15 °C, respectively, thereby transforming them from negligible into high monoterpene emitters. The observed emission increase was substantially higher than the model-predicted increase of 3.7-fold (ΔT = 13 °C) and 4.5-fold (ΔT = 15 °C). We demonstrate that current emission algorithms cannot accurately model the emission behavior of these plant species at the high temperatures that are characteristic of severe heatwaves. Furthermore, monoterpene emissions from western redcedar and American sweetgum remained elevated for 1–7 days after the heat stress. In contrast to the other three species, red ironbark was a significant constitutive monoterpene emitter (at 30 °C) and its emission response to temperature was close to model predictions. Each of the four species investigated in this study possesses specialized foliar terpene-storing structures, for example, glandular trichomes and oil glands. The strong monoterpene emission induction observed in some of these species may be attributed to heat-induced damage to these storage structures. However, the wall permeability of these structures may vary by species and could limit the magnitude of the heat-induced emission response.

  2. Vettikkat L, Miettinen P, Buchholz A, Rantala P, Yu H, Schallhart S, Petäjä T, Seco R, Männistö E, Kulmala M, Tuittila E-S, Guenther AB, and Schobesberger S (2023) High emission rates and strong temperature response make boreal wetlands a large source of isoprene and terpenes. Atmospheric Chemistry and Physics, 23: 2683–2698. Supplement Data Abstract

    Wetlands cover only 3 % of the global land surface area, but boreal wetlands are experiencing an unprecedented warming of four times the global average. These wetlands emit isoprene and terpenes (including monoterpenes (MT), sesquiterpenes (SQT), and diterpenes (DT)), which are climate-relevant highly reactive biogenic volatile organic compounds (BVOCs) with an exponential dependence on temperature. In this study, we present ecosystem-scale eddy covariance (EC) fluxes of isoprene, MT, SQT, and DT (hereafter referred to together as terpenes) at Siikaneva, a boreal fen in southern Finland, from the start to the peak of the growing season of 2021 (19 May 2021 to 28 June 2021). These are the first EC fluxes reported using the novel state-of-the-art Vocus proton transfer reaction mass spectrometer (Vocus-PTR) and the first-ever fluxes reported for DTs from a wetland. Isoprene was the dominant compound emitted by the wetland, followed by MTs, SQTs, and DTs, and they all exhibited a strong exponential temperature dependence. The Q10 values, the factor by which terpene emissions increases for every 10 °C rise in temperature, were up to five times higher than those used in most BVOC models. During the campaign, the air temperature peaked above 31 °C on 21–22 June 2021, which is abnormally high for boreal environments, and the maximum flux for all terpenes coincided with this period. We observed that terpene emissions were elevated after this abnormally “high-temperature stress period”, indicating that past temperatures alter emissions significantly. The standardized emission factor (EF) of the fen for isoprene (EFiso) was 11.1 ± 0.3 nmol m-2 s-1, which is at least two times higher than in previous studies and as high as the emission factors typical for broadleaf and other forests in the lower latitudes. We observed EFMT of 2.4 ± 0.1 nmol m-2 s-1, EFSQT of 1.3 ± 0.03 nmol m-2 s-1, higher than typical for needle leaf and broadleaf tree functional types, and EFDT of 0.011 ± 0.001 nmol m-2 s-1. We also compared the landscape average emissions to the model of emissions of gases and aerosols from nature (MEGAN) v2.1 and found that the emissions were underestimated by over 9 times for isoprene, over 300 times for MTs, and 800 times for SQTs. Our results show that due to very high EFs and high sensitivity to increasing temperatures, these high-latitude ecosystems can be a large source of terpenes to the atmosphere, and anthropogenic global warming could induce much higher BVOC emissions from wetlands in the future.

  3. DiMaria CA, Jones DBA, Worden H, Bloom AA, Bowman K, StavrakouT, Miyazaki K, Worden J, Guenther A, Sarkar C, Seco R, Park J-H, Tota J, Gomes Alves E, Ferracci V (2023) Optimizing the isoprene emission model MEGAN with satellite and ground-based observational constraints. Journal of Geophysical Research: Atmospheres, 128: e2022JD037822. Supplement Abstract

    Isoprene is a hydrocarbon emitted in large quantities by terrestrial vegetation. It is a precursor to several air quality and climate pollutants including ozone. Emission rates vary with plant species and environmental conditions. This variability can be modeled using the Model of Emissions of Gases and Aerosols from Nature (MEGAN). MEGAN parameterizes isoprene emission rates as a vegetation-specific standard rate which is modulated by scaling factors that depend on meteorological and environmental driving variables. Recent experiments have identified large uncertainties in the MEGAN temperature response parameterization, while the emission rates under standard conditions are poorly constrained in some regions due to a lack of representative measurements and uncertainties in landcover. In this study, we use Bayesian model-data fusion to optimize the MEGAN temperature response and standard emission rates using satellite- and ground-based observational constraints. Optimization of the standard emission rate with satellite constraints reduced model biases but was highly sensitive to model input errors and drought stress and was found to be inconsistent with ground-based constraints at an Amazonian field site, reflecting large uncertainties in the satellite-based emissions. Optimization of the temperature response with ground-based constraints increased the temperature sensitivity of the model by a factor of five at an Amazonian field site but had no impact at a UK field site, demonstrating significant ecosystem-dependent variability of the isoprene emission temperature sensitivity. Ground-based measurements of isoprene across a wide range of ecosystems will be key for obtaining an accurate representation of isoprene emission temperature sensitivity in global biogeochemical models.

  4. Li T, Baggesen N, Seco R, Rinnan R (2023) Seasonal and diel patterns of biogenic volatile organic compound fluxes in a subarctic tundra. Atmospheric Environment, 292: 119430. Supplement 1 Supplement 2 Abstract

    In arctic and subarctic regions, rapid climate changes enhance biogenic volatile organic compound (BVOC) emissions from vegetation, with potentially significant influence on atmospheric processes. However, the seasonal and diel patterns of bidirectional exchange (flux) of BVOCs remain poorly studied in these regions. Here, we deployed a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) to investigate ecosystem-level BVOC fluxes over a growing season in a subarctic tundra heath in Abisko, Northern Sweden, and to quantify BVOC emissions from two widespread dwarf shrubs in the high latitudes, Salix myrsinites and Betula nana. As expected, ecosystem fluxes of short-chained oxygenated compounds (e.g., methanol, acetaldehyde and acetone) and terpenoids (e.g., isoprene, monoterpenes and sesquiterpenes) followed different seasonal and diel patterns. For the short-chained oxygenated compounds, net emissions dominated and peaked in the early growing season, while net deposition occurred sporadically, particularly at night. In contrast, terpenoids were almost exclusively emitted from the ecosystem, with maxima occurring in the peak growing season. At the branch level, these compound groups were emitted from both S. myrsinites and B. nana in clear diel patterns with high emissions during the day. S. myrsinites was dominated by isoprene emissions whilst B. nana was dominated by terpene emissions. Methanol, acetaldehyde and acetone were emitted at comparable levels and similar patterns from both species. Both ecosystem fluxes and branch emissions responded exponentially to enclosure temperature and depended on light levels. Compared to the BVOC emission models, however, the temperature responses were steeper for isoprene, monoterpenes, methanol and acetone, but weaker for sesquiterpenes. Apart from the well-known compounds, many other BVOCs, such as some carbonyls and nitrogen-containing compounds, were emitted from both the ecosystem and plants with significant contributions to the season variation in ecosystem fluxes. Overall, our study highlights the complexity of subarctic ecosystem BVOC fluxes, which vary both seasonally and diurnally. Vegetation composition changes triggered by climate change will shift BVOC composition, with important implications for atmospheric processes and local climate.

  5. 2022

  6. Wang H, Lu X, Seco R, Stavrakou T, Karl T, Jiang X, Gu L, Guenther AB (2022) Modeling isoprene emission response to drought and heatwaves within MEGAN using evapotranspiration data and by coupling with the Community Land Model. Journal of Advances in Modeling Earth Systems, 14: e2022MS003174. Supplement Abstract

    We introduce two new drought stress algorithms designed to simulate isoprene emission with the Model of Emissions of Gases and Aerosols from Nature (MEGAN) model. The two approaches include the representation of the impact of drought on isoprene emission with a simple empirical approach for offline MEGAN applications and a more process-based approach for online MEGAN in Community Land Model (CLM) simulations. The two versions differ in their implementation of leaf-temperature impacts of mild drought. For the online version of MEGAN that is coupled to CLM, the impact of drought on leaf temperature is simulated directly and the calculated leaf temperature is considered for the estimation of isoprene emission. For the offline version, we apply an empirical algorithm derived from whole-canopy flux measurements for simulating the impact of drought ranging from mild to severe stage. In addition, the offline approach adopts the ratio (fPET) of actual evapotranspiration to potential evapotranspiration to quantify the severity of drought instead of using soil moisture. We applied the two algorithms in the CLM-CAM-chem (the Community Atmosphere Model with Chemistry) model to simulate the impact of drought on isoprene emission and found that drought can decrease isoprene emission globally by 11% in 2012. We further compared the formaldehyde (HCHO) vertical column density simulated by CAM-chem to satellite HCHO observations. We found that the proposed drought algorithm can improve the match with the HCHO observations during droughts, but the performance of the drought algorithm is limited by the capacity of the model to capture the severity of drought.

  7. Wang Y, Lin N, Li W, Guenther A, Lam JCY, Tai APK, Potosnak MJ, Seco R (2022) Satellite-derived Constraints on the Effect of Drought Stress on Biogenic Isoprene Emissions in the Southeast US. Atmospheric Chemistry and Physics, 22: 14189–14208 (17 MB) Supplement Abstract

    While substantial progress has been made to improve our understanding of biogenic isoprene emissions under unstressed conditions, large uncertainties remain with respect to isoprene emissions under stressed conditions. Here, we use the US Drought Monitor (USDM) as a weekly drought severity index and tropospheric columns of formaldehyde (HCHO), the key product of isoprene oxidation, retrieved from the Ozone Monitoring Instrument (OMI) to derive top-down constraints on the response of summertime isoprene emissions to drought stress in the southeastern United States (SE US), a region of high isoprene emissions that is also prone to drought. OMI HCHO column density is found to be 6.7 % (mild drought) to 23.3 % (severe drought) higher than that under non-drought conditions. A global chemical transport model, GEOS-Chem, with version 2.1 of the Model of Emissions of Gases and Aerosols from Nature (MEGAN2.1) emission algorithm can simulate this direction of change, but the simulated increases at the corresponding drought levels are 1.1–1.5 times that of OMI HCHO, suggesting the need for a drought-stress algorithm in the model. By minimizing the model–OMI differences in HCHO to temperature sensitivity under different drought levels, we derived a top-down drought stress factor (γd_OMI) in GEOS-Chem that parameterizes using water stress and temperature. The algorithm led to an 8.6 % (mild drought) to 20.7 % (severe drought) reduction in isoprene emissions in the SE US relative to the simulation without it. With γd_OMI the model predicts a nonlinear increasing trend in isoprene emissions with drought severity that is consistent with OMI HCHO and a single site's isoprene flux measurements. Compared with a previous drought stress algorithm derived from the latter, the satellite-based drought stress factor performs better with respect to capturing the regional-scale drought–isoprene responses, as indicated by the near-zero mean bias between OMI and simulated HCHO columns under different drought conditions. The drought stress algorithm also reduces the model's high bias in organic aerosol (OA) simulations by 6.60 % (mild drought) to 11.71 % (severe drought) over the SE US compared to the no-stress simulation. The simulated ozone response to the drought stress factor displays a spatial disparity due to the isoprene-suppressing effect on oxidants, with an <1 ppb increase in O3 in high-isoprene regions and a 1–3 ppbv decrease in O3 in low-isoprene regions. This study demonstrates the unique value of exploiting long-term satellite observations to develop empirical stress algorithms on biogenic emissions where in situ flux measurements are limited.

  8. Seco R, Holst T, Davie-Martin CL, Simin T, Guenther A, Pirk N, Rinne J, Rinnan R (2022) Strong isoprene emission response to temperature in tundra vegetation. Proceedings of the National Academy of Sciences of the USA, 119: e2118014119 Supplement Data Abstract

    Emissions of biogenic volatile organic compounds (BVOCs) are a crucial component of biosphere–atmosphere interactions. In northern latitudes, climate change is amplified by feedback processes in which BVOCs have a recognized, yet poorly quantified role, mainly due to a lack of measurements and concomitant modeling gaps. Hence, current Earth system models mostly rely on temperature responses measured on vegetation from lower latitudes, rendering their predictions highly uncertain. Here, we show how tundra isoprene emissions respond vigorously to temperature increases, compared to model results. Our unique dataset of direct eddy covariance ecosystem-level isoprene measurements in two contrasting ecosystems exhibited Q10 (the factor by which the emission rate increases with a 10 °C rise in temperature) temperature coefficients of up to 20.8, that is, 3.5 times the Q10 of 5.9 derived from the equivalent model calculations. Crude estimates using the observed temperature responses indicate that tundra vegetation could enhance their isoprene emissions by up to 41% (87%)—that is, 46% (55%) more than estimated by models—with a 2 °C (4 °C) warming. Our results demonstrate that tundra vegetation possesses the potential to substantially boost its isoprene emissions in response to future rising temperatures, at rates that exceed the current Earth system model predictions.

      Featured in the "In this issue" section of PNAS
  9. Myers DC, Kim S, Sjostedt S, Guenther AB, Seco R, Vega Bustillos O, Tota J, Souza RAF, Smith JN (2022) Sulfuric acid in the Amazon basin: measurements and evaluation of existing sulfuric acid proxies. Atmospheric Chemistry and Physics, 22: 10061–10076 Supplement Abstract

    Sulfuric acid is a key contributor to new particle formation, though measurements of its gaseous concentrations are difficult to make. Several parameterizations to estimate sulfuric acid exist, all of which were constructed using measurements from the Northern Hemisphere. In this work, we report the first measurements of sulfuric acid from the Amazon basin. These measurements are consistent with concentrations measured in Hyytiälä, Finland, though, unlike Hyytiälä, there is no clear correlation of sulfuric acid with global radiation. There was a minimal difference in sulfuric acid observed between the wet and dry seasons in the Amazon basin. We also test the efficacy of existing proxies to estimate sulfuric acid in this region. Our results suggest that nighttime sulfuric acid production is due to both a stabilized Criegee intermediate pathway and oxidation of SO2 by OH, the latter of which is not currently accounted for in existing proxies. These results also illustrate the drawbacks of the common substitution of radiation for OH concentrations. None of the tested proxies effectively estimate sulfuric acid measurements at night. For estimates at all times of day, a recently published proxy based on data from the boreal forest should be used. If only daytime estimates are needed, several recent proxies that do not include the Criegee pathway are sufficient. More investigation of nighttime sulfuric acid production pathways is necessary to close the gap between measurements and estimates with existing proxies.

  10. Baggesen N, Davie-Martin CL, Seco R, Holst T , Rinnan R (2022) Bidirectional exchange of biogenic volatile organic compounds in subarctic heath mesocosms during autumn climate scenarios.
    Journal of Geophysical Research - Biogeosciences, 127: e2021JG006688 Supplement Abstract

    Biogenic volatile organic compound (BVOC) flux dynamics during the subarctic autumn are largely unexplored and have been considered insignificant due to the relatively low biological activity expected during autumn. Here, we exposed subarctic heath ecosystems to predicted future autumn climate scenarios (ambient, warming, and colder, dark conditions), changes in light availability, and flooding, to mimic the more extreme rainfall or snowmelt events expected in the future. We used climate chambers to measure the net ecosystem fluxes and bidirectional exchange of BVOCs from intact heath mesocosms using a dynamic enclosure technique coupled to a proton-transfer-reaction time-of-flight mass spectrometer (PTR–ToF–MS). We focused on six BVOCs (methanol, acetic acid, acetaldehyde, acetone, isoprene, and monoterpenes) that were among the most dominant and that were previously identified in arctic tundra ecosystems. Warming increased ecosystem respiration and resulted in either net BVOC release or increased uptake compared to the ambient scenario. None of the targeted BVOCs showed net release in the cold and dark scenario. Acetic acid exhibited significantly lower net uptake in the cold and dark scenario than in the ambient scenario, which suggests reduced microbial activity. Flooding was characterized by net uptake of the targeted BVOCs and overruled any temperature effects conferred by the climate scenarios. Monoterpenes were mainly taken up by the mesocosms and their fluxes were not affected by the climate scenarios or flooding. This study shows that although autumn BVOC fluxes on a subarctic heath are generally low, changes in future climate may strongly modify them.

  11. Opacka B, Müller J-F, Stavrakou T, Miralles DG, Koppa A, Pagán BR, Potosnak MJ, Seco R, De Smedt I, Guenther AB (2022) Impact of drought on isoprene fluxes assessed using field data, satellite-based GLEAM soil moisture and HCHO observations from OMI. Remote Sensing, 14 (9): 2021 Supplement Abstract

    Biogenic volatile organic compounds (BVOCs), primarily emitted by terrestrial vegetation, are highly reactive and have large effects on the oxidizing potential of the troposphere, air quality and climate. In terms of global emissions, isoprene is the most important BVOC. Droughts bring about changes in the surface emission of biogenic hydrocarbons mainly because plants suffer water stress. Past studies report that the current parameterization in the state-of-the-art Model of Emissions of Gases and Aerosols from Nature (MEGAN) v2.1, which is a function of the soil water content and the permanent wilting point, fails at representing the strong reduction in isoprene emissions observed in field measurements conducted during a severe drought. Since the current algorithm was originally developed based on potted plants, in this study, we update the parameterization in the light of recent ecosystem-scale measurements of isoprene conducted during natural droughts in the central U.S. at the Missouri Ozarks AmeriFlux (MOFLUX) site. The updated parameterization results in stronger reductions in isoprene emissions. Evaluation using satellite formaldehyde (HCHO), a proxy for BVOC emissions, and a chemical-transport model, shows that the adjusted parameterization provides a better agreement between the modelled and observed HCHO temporal variability at local and regional scales in 2011–2012, even if it worsens the model agreement in a global, long-term evaluation. We discuss the limitations of the current parameterization, a function of highly uncertain soil properties such as porosity.

  12. Lei Y, Yue X, Liao H, Zhang L, Zhou H, Tian C, Gong C, Ma Y, Cao Y, Seco R, Karl T, Potosnak M (2022) Global perspective of drought impacts on ozone pollution episodes. Environmental Science & Technology, 56: 3932-3940 Supplement Abstract

    Ozone (O3) pollution threatens global public health and damages ecosystem productivity. Droughts modulate surface O3 through meteorological processes and vegetation feedbacks. Unraveling these influences is difficult with traditional chemical transport models. Here, using an atmospheric chemistry–vegetation coupled model in combination with a suite of existing measurements, we investigate the drought impacts on global surface O3 and explore the main driving processes. Relative to the mean state, accelerated photochemical rates dominate the surface O3 enhancement during droughts except for eastern U.S. and western Europe, where reduced stomatal uptakes make comparable contributions. During 1990–2012, the simulated frequency of O3 pollution episodes in western Europe decreases greatly with a negative trend of -5.5 ± 6.6 days per decade following the reductions in anthropogenic emissions if meteorology is fixed. However, such decreased trend is weakened to -2.1 ± 3.8 days per decade, which is closer to the observed trend of -2.9 ± 1.1 days per decade when year-to-year meteorology is applied because increased droughts alone offset 43% of the effects from air pollution control. Our results highlight that more stringent controls of O3 precursors are necessary to mitigate the higher risks of O3 pollution episodes by more droughts in a warming world.

  13. Nagalingam S, Seco R, Musaev K, Basu C, Kim S, Guenther A (2022) Impact of heat stress on foliar biogenic volatile organic compound emission and gene expression in tomato (Solanum lycopersicum) seedlings. Elementa: Science of the Anthropocene, 10: 00096 Supplement Supp S1 Supp S2 Abstract

    We present foliar biogenic volatile organic compound (BVOC) emission data from 24-h heat-stressed tomato (Solanum lycopersicum) seedlings including speciated monoterpenes and sesquiterpenes and high time-resolution measurements of methyl salicylate and total monoterpenes. The median total monoterpene and total sesquiterpene emission rates at 30°C were 18.5 and 0.172 pmol m–2 s–1, respectively, which falls within the negligible emission category of previous studies. However, initial heat exposure (39°C or 42°C) increased the emissions of approximately half of the targeted compounds beyond what was predicted by current BVOC emission temperature response algorithms. The enhanced emissions were not always sustained for the entire duration of the heat stress and some plants exhibited a delayed monoterpene response, where emissions peaked toward the end of the heat treatment. Methyl salicylate, a known stress marker, responded differently to the heat stress than most of the other compounds. Heat stress increased methyl salicylate emissions in some plants (at least initially), but in others, emissions declined or did not change significantly. There was no significant correlation between the magnitude of gene expression and emission induction of monoterpenes or methyl salicylate. Furthermore, the emitted monoterpenes did not exhibit any apparent light-dependent behavior, which suggests that these monoterpene stress emissions mostly originated from light-independent foliar storage pools and not from increased de novo production. In contrast, methyl salicylate emissions appear to have contributions from both de novo synthesis and stored pools, as they showed both enzyme-controlled (i.e., light-dependent) and light-independent behaviors. Analyses of the foliar essential oils demonstrate that most of the emitted BVOCs were also present in stored pools. The pool sizes were generally large enough to sustain unstressed emission levels for days to months, and even years for some compounds. However, heat-induced emission enhancement can diminish the pool sizes of some BVOCs, which could decrease subsequent emissions.

  14. Jeong D, Seco R, Emmons L, Schwantes R, Liu Y, McKinney KA, Martin ST, Keutsch FN, Gu D, Guenther AB, Vega O, Tota J, Souza RAF, Springston SR, Watson TB, Kim S (2022) Reconciling Observed and Predicted Tropical Rainforest OH Concentrations. Journal of Geophysical Research: Atmospheres, 127: e2020JD032901 Supplement Abstract

    We present OH observations made in Amazonas, Brazil during the Green Ocean Amazon campaign (GoAmazon2014/5) from February to March of 2014. The average diurnal variation of OH peaked with a midday (10:00–15:00) average of 1.0 × 106 (±0.6 × 106) molecules cm-3. This was substantially lower than previously reported in other tropical forest photochemical environments (2–5 × 106 molecules cm-3) while the simulated OH reactivity was lower. The observational data set was used to constrain a box model to examine how well current photochemical reaction mechanisms can simulate observed OH. We used one near-explicit mechanism (MCM v3.3.1) and four condensed mechanisms (i.e., RACM2, MOZART-T1, CB05, CB6r2) to simulate OH. A total of 14 days of analysis shows that all five chemical mechanisms were able to explain the measured OH within instrumental uncertainty of 40% during the campaign in the Amazonian rainforest environment. Future studies are required using more reliable NOx and VOC measurements to further investigate discrepancies in our understanding of the radical chemistry in the tropical rainforest.

  15. 2021

  16. Yáñez-Serrano AM, Bach A, Bartolomé-Català D, Matthaios V, Seco R, Llusia J, Filella I, Peñuelas J (2021) Dynamics of volatile organic compounds in a western Mediterranean oak forest. Atmospheric Environment, 257: 118447 Supplement Abstract

    • We analysed the below canopy volatile organic compounds of a Mediterranean forest of the Iberian Peninsula for six months.
    • Biogenic VOC emissions dominated at the forest, but there was strong influence from anthropogenic sources from elsewhere.
    • We identified photochemical VOC production, biogenic, mixed VOC, and traffic emissions sources.
    • We show how the atmospheres of forested ecosystems could be substantially affected by anthropogenic VOC sources.
    Volatile organic compounds (VOCs) are emitted from many sources and have important implications for plant fitness, ecological interactions, and atmospheric processes, including photochemistry and ozone formation. Forest ecosystems are strong sources of biogenic VOCs. We aimed to characterize forest below-canopy VOC mixing ratios, monitored by Proton Transfer Reaction Mass Spectrometry (PTR-MS), at Montseny Natural Park, a Mediterranean forest 50 km from the Barcelona urban area. Measurements were taken every 2 min during six months around the maximum emission period of summer. All VOCs had diel cycles with higher mixing ratios during the day, but different patterns over time. Monitored VOCs were grouped as biogenic, oxygenated, or aromatic compounds. Additionally, a positive matrix factorization analysis identified four emission profiles that were attributed to photochemical VOC production, biogenic emissions, mixed VOC emission sources, and traffic emissions. Even though the biogenic source was the strongest source profile at the site, we found a strong influence of anthropogenic air masses infiltrating the forest canopy and altering the biogenic air masses at the site.

  17. Baggesen N, Li T, Seco R, Holst T, Michelsen A, Rinnan R (2021) Phenological stage of tundra vegetation controls bidirectional exchange of BVOCs in a climate change experiment on a Subarctic heath. Global Change Biology, 27: 2928-2944 Supplement Abstract

    Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long-term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem-level net BVOC fluxes were measured in the experimental plots using proton-transfer-reaction time-of-flight mass spectrometry (PTR–ToF–MS). The warming treatment increased monoterpene and isoprene emissions by ˜50%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by ~50%–75%) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interact and influence BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not only a response to changes in temperature and light intensity, as the circadian clock also affects emission rates.

  18. Sanchez D, Seco R, Gu D, Guenther A, Mak J, Lee Y, Kim D, Ahn J, Blake D, Herndon S, Jeong D, Sullivan JT, Mcgee T, Park R, Kim S (2021) Contributions to OH reactivity from unexplored volatile organic compounds measured by PTR-ToF-MS – a case study in a suburban forest of the Seoul metropolitan area during the Korea–United States Air Quality Study (KORUS-AQ) 2016. Atmospheric Chemistry and Physics, 21: 6331–6345 Supplement Abstract

    We report OH reactivity observations by a chemical ionization mass spectrometer–comparative reactivity method (CIMS-CRM) instrument in a suburban forest of the Seoul metropolitan area (SMA) during the Korea–United States Air Quality Study (KORUS-AQ 2016) from mid-May to mid-June of 2016. A comprehensive observational suite was deployed to quantify reactive trace gases inside of the forest canopy including a high-resolution proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS). An average OH reactivity of 30.7±5.1 s-1 was observed, while the OH reactivity calculated from CO, NO+NO2 (NOx), ozone (O3), sulfur dioxide (SO2), and 14 volatile organic compounds (VOCs) was 11.8±1.0 s-1. An analysis of 346 peaks from the PTR-ToF-MS accounted for an additional 6.0±2.2 s-1 of the total measured OH reactivity, leaving 42.0 % missing OH reactivity. A series of analyses indicate that the missing OH reactivity most likely comes from VOC oxidation products of both biogenic and anthropogenic origin.

  19. Kim S, Seco R, Dasa Gu, Sanchez S, Jeong D, Guenther AB, Lee Y-R, Mak JE, Su L, Kim DB, Ahn J, Sullivan J, Mcgee T, Long R, Brune WH, Thames A, Wisthaler A, Müller M, Weinheimer A, Mikoviny T, Yang M, Woo J-H, Kim S, Park H (2021) The role of a suburban forest in controlling vertical trace gas and OH reactivity distributions – a case study for the Seoul metropolitan area. Faraday Discussions, 226: 537-550 Supplement Abstract

    We present trace gas vertical profiles observed by instruments on the NASA DC-8 and at a ground site during the Korea-US air quality study (KORUS) field campaign in May to June 2016. We focus on the region near the Seoul metropolitan area and its surroundings where both anthropogenic and natural emission sources play an important role in local photochemistry. Integrating ground and airborne observations is the major research goal of many atmospheric chemistry field campaigns. Although airborne platforms typically aim to sample from near surface to the free troposphere, it is difficult to fly very close to the surface especially in environments with complex terrain or a populated area. A detailed analysis integrating ground and airborne observations associated with specific concentration footprints indicates that reactive trace gases are quickly oxidized below an altitude of 700 m. The total OH reactivity profile has a rapid decay in the lower part of troposphere from surface to the lowest altitude (700 m) sampled by the NASA DC-8. The decay rate is close to that of very reactive biogenic volatile organic compounds such as monoterpenes. Therefore, we argue that photochemical processes in the bottom of the boundary layer, below the typical altitude of aircraft sampling, should be thoroughly investigated to properly assess ozone and secondary aerosol formation.

  20. Yáñez-Serrano AM, Filella I, Llusià J, Gargallo-Garriga A, Granda V, Bourtsoukidis E, Williams J, Seco R, Cappellin L, Werner C, de Gouw J, Peñuelas J (2021) GLOVOCs - Master compound assignment guide for proton transfer reaction mass spectrometry users. Atmospheric Environment, 244: 117929 Supplement Abstract

    • We have created GLOVOCS, a master compound assignment guide that can be referred to by PTR-MS practitioners.
    • GLOVOCS is aimed to help in advancing science of VOCs by facilitating the research of multiple groups using PTR-MS.
    • GLOVOCS, accessible at, is a collaborative tool where users can both consult and contribute to.
    The richness of measurements obtained by Proton-Transfer Reactions Mass Spectrometry (PTR-MS) has opened a new paradigm for the quantification of volatile organic compounds (VOCs). A wide range of compounds can be monitored, however, each detected signal is subject to a compound assignment instead of actual identification because PTR techniques are mass-selective and isomers cannot be separately measured. Thus, rapid development in the field requests continued community efforts to identify compounds. In this study we have reviewed the available literature and created a master compound assignment guide called GLOVOCS that can be referred to by PTR-MS practitioners. GLOVOCS is aimed to help in advancing science of VOCs by facilitating the research of multiple groups using PTR-MS to monitor VOCs and to disentangle the physical, chemical and biological mechanisms underlying their production, emission and impact on environment and organisms from bacteria to humans. The guide is freely accessible at as a collaborative tool, where users can both consult and contribute to the identification of VOCs by providing possible candidates for all chemical formulas from 18 to 330 atomic mass units. When available, we indicate if there is evidence for biogenic or anthropogenic VOC origin, as well as grouping the compounds based on the Classyfire chemotaxonomic classification (Djoumbou Feunang et al., 2016). While GLOVOCS aims to facilitate the first assessment and consistent classification of compounds, we highly recommend further cross-validation for verifying compounds when using PTR-MS techniques.

  21. 2020

  22. Seco R, Holst T, Matzen MS, Westergaard-Nielsen A, Li T, Simin T, Jansen J, Crill P, Friborg T, Rinne J, Rinnan R (2020) Volatile organic compound fluxes in a subarctic peatland and lake. Atmospheric Chemistry and Physics, 20: 13399–13416 Supplement Data Abstract

    Ecosystems exchange climate-relevant trace gases with the atmosphere, including volatile organic compounds (VOCs) that are a small but highly reactive part of the carbon cycle. VOCs have important ecological functions and implications for atmospheric chemistry and climate. We measured the ecosystem-level surface–atmosphere VOC fluxes using the eddy covariance technique at a shallow subarctic lake and an adjacent graminoid-dominated fen in northern Sweden during two contrasting periods: the peak growing season (mid-July) and the senescent period post-growing season (September–October).

    In July, the fen was a net source of methanol, acetaldehyde, acetone, dimethyl sulfide, isoprene, and monoterpenes. All of these VOCs showed a diel cycle of emission with maxima around noon and isoprene dominated the fluxes (93±22 µmol m-2 d-1, mean ± SE). Isoprene emission was strongly stimulated by temperature and presented a steeper response to temperature (Q10=14.5) than that typically assumed in biogenic emission models, supporting the high temperature sensitivity of arctic vegetation. In September, net emissions of methanol and isoprene were drastically reduced, while acetaldehyde and acetone were deposited to the fen, with rates of up to -6.7±2.8 µmol m-2 d-1 for acetaldehyde.

    Remarkably, the lake was a sink for acetaldehyde and acetone during both periods, with average fluxes up to -19±1.3 µmol m-2 d-1 of acetone in July and up to -8.5±2.3 µmol m-2 d-1 of acetaldehyde in September. The deposition of both carbonyl compounds correlated with their atmospheric mixing ratios, with deposition velocities of -0.23±0.01 and -0.68±0.03 cm s-1 for acetone and acetaldehyde, respectively.

    Even though these VOC fluxes represented less than 0.5 % and less than 5 % of the CO2 and CH4 net carbon ecosystem exchange, respectively, VOCs alter the oxidation capacity of the atmosphere. Thus, understanding the response of their emissions to climate change is important for accurate prediction of the future climatic conditions in this rapidly warming area of the planet.

  23. Powers JM, Seco R, Faiola CL, Sakai AK, Weller SG, Campbell DR, Guenther A (2020) Floral scent composition and fine-scale timing in two moth-pollinated Hawaiian Schiedea (Caryophyllaceae). Frontiers in Plant Science, 11: 1116 Supplement Data Abstract

    Floral scent often intensifies during periods of pollinator activity, but the degree of this synchrony may vary among scent compounds depending on their function. Related plant species with the same pollinator may exhibit similar timing and composition of floral scent. We compared timing and composition of floral volatiles for two endemic Hawaiian plant species, Schiedea kaalae and S. hookeri (Caryophyllaceae). For S. kaalae, we also compared the daily timing of emission of floral volatiles to evening visits of their shared pollinator, an endemic Hawaiian moth (Pseudoschrankia brevipalpis; Erebidae). The identity and amount of floral volatiles were measured in the greenhouse during day and evening periods with dynamic headspace sampling and GC-MS (gas chromatography – mass spectrometry). The timing of emissions (daily rise, peak, and fall) was measured by sampling continuously for multiple days in a growth chamber with PTR-MS (proton transfer reaction mass spectrometry). Nearly all volatiles detected underwent strong daily cycles in emission. Timings of floral volatile emissions were similar for S. kaalae and S. hookeri, as expected for two species sharing the same pollinator. For S. kaalae, many volatiles known to attract moths, including several linalool oxides and 2-phenylacetaldehyde, peaked within 2 h of the peak visitation time of the moth which pollinates both species. Floral volatiles of both species that peaked in the evening were also emitted several hours before and after the brief window of pollinator activity. Few volatiles followed a daytime emission pattern, consistent with increased apparency to visitors only at night. The scent blends of the two species differed in their major components and were most distinct from each other in the evening. The qualitative difference in evening scent composition between the two Schiedea species may reflect their distinct evolutionary history and may indicate that the moth species uses several different floral cues to locate rewards.

  24. Sarkar C, Guenther AB, Park J-H, Seco R, Alves E, Batalha S, Santana R, Kim S, Smith J, Tóta J, Vega O (2020) PTR-TOF-MS eddy covariance measurements of isoprene and monoterpene fluxes from an eastern Amazonian rainforest. Atmospheric Chemistry and Physics, 20: 7179–7191 Abstract

    Biogenic volatile organic compounds (BVOCs) are important components of the atmosphere due to their contribution to atmospheric chemistry and biogeochemical cycles. Tropical forests are the largest source of the dominant BVOC emissions (e.g. isoprene and monoterpenes). In this study, we report isoprene and total monoterpene flux measurements with a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) using the eddy covariance (EC) method at the Tapajós National Forest (2.857° S, 54.959° W), a primary rainforest in eastern Amazonia. Measurements were carried out from 1 to 16 June 2014, during the wet-to-dry transition season. During the measurement period, the measured daytime (06:00–18:00 LT) average isoprene mixing ratios and fluxes were 1.15±0.60 ppb and 0.55±0.71 mg C m-2 h-1, respectively, whereas the measured daytime average total monoterpene mixing ratios and fluxes were 0.14±0.10 ppb and 0.20±0.25 mg C m-2 h-1, respectively. Midday (10:00–14:00 LT) average isoprene and total monoterpene mixing ratios were 1.70±0.49 and 0.24±0.05 ppb, respectively, whereas midday average isoprene and monoterpene fluxes were 1.24±0.68 and 0.46±0.22 mg C m-2 h-1, respectively. Isoprene and total monoterpene emissions in Tapajós were correlated with ambient temperature and solar radiation. Significant correlation with sensible heat flux, SHF (r2=0.77), was also observed. Measured isoprene and monoterpene fluxes were strongly correlated with each other (r2=0.93). The MEGAN2.1 (Model of Emissions of Gases and Aerosols from Nature version 2.1) model could simulate most of the observed diurnal variations (r2=0.7 to 0.8) but declined a little later in the evening for both isoprene and total monoterpene fluxes. The results also demonstrate the importance of site-specific vegetation emission factors (EFs) for accurately simulating BVOC fluxes in regional and global BVOC emission models.

  25. 2019

  26. Jeong D, Seco R, Gu D, Lee Y, Nault BA, Knote CJ, Mcgee T, Sullivan JT, Jimenez JL, Campuzano-Jost P, Blake DR, Sanchez D, Guenther AB, Tanner D, Huey LG, Long R, Anderson BE, Hall SR, Ullmann K, Shin H, Herndon SC, Lee Y, Kim D, Ahn J, Kim S (2019) Integration of airborne and ground observations of nitryl chloride in the Seoul metropolitan area and the implications on regional oxidation capacity during KORUS-AQ 2016. Atmospheric Chemistry and Physics 19: 12779–12795 Supplement Abstract

    Nitryl chloride (ClNO2) is a radical reservoir species that releases chlorine radicals upon photolysis. An integrated analysis of the impact of ClNO2 on regional photochemistry in the Seoul metropolitan area (SMA) during the Korea–United States Air Quality Study (KORUS-AQ) 2016 field campaign is presented. Comprehensive multiplatform observations were conducted aboard the NASA DC-8 and at two ground sites (Olympic Park, OP; Taehwa Research Forest, TRF), representing an urbanized area and a forested suburban region, respectively. Positive correlations between daytime Cl2 and ClNO2 were observed at both sites, the slope of which was dependent on O3 levels. The possible mechanisms are explored through box model simulations constrained with observations. The overall diurnal variations in ClNO2 at both sites appeared similar but the nighttime variations were systematically different. For about half of the observation days at the OP site the level of ClNO2 increased at sunset but rapidly decreased at around midnight. On the other hand, high levels were observed throughout the night at the TRF site. Significant levels of ClNO2 were observed at both sites for 4–5 h after sunrise. Airborne observations, box model calculations, and back-trajectory analysis consistently show that these high levels of ClNO2 in the morning are likely from vertical or horizontal transport of air masses from the west. Box model results show that chlorine-radical-initiated chemistry can impact the regional photochemistry by elevating net chemical production rates of ozone by ~25 % in the morning.

  27. Li L, Guenther AB, Xie S, Gu D, Seco R, Nagalingam S, Yan D (2019) Evaluation of semi-static enclosure technique for rapid surveys of biogenic volatile organic compounds (BVOCs) emission measurements. Atmospheric Environment, 212: 1-5 Supplement Abstract

    • Semi-static method cannot provide consistent measurements for VOCs stored in leaf.
    • The measured isoprene emission factors are much higher than dynamic measurements.
    • Semi-static technique can detect fewer compounds than dynamic one.
    Biogenic volatile organic compounds (BVOCs) are important drivers of atmospheric chemical composition and accurate model simulations require characterization of the emissions associated with specific vegetation types which is typically determined using enclosure measurements. Static enclosure techniques were used for past BVOC emission measurement studies, especially in the 1960s–1980s, but are no longer widely used because of concerns that the resulting emission rates are not representative. The main advantages of the static approach are the capability for rapid measurements and a lower detection limit that enables the use of less sensitive analytical techniques. We evaluate a version of the static approach which we call the semi-static approach. In order to evaluate the performance of the semi-static approach for BVOCs emission measurements, multiple replicate measurements for different plants were conducted in a laboratory growth chamber using both semi-static and dynamic enclosure techniques. Variability of replicate measurements was calculated and the results from the two techniques were compared. The semi-static technique provided consistent measurements for isoprene but not for a-pinene, ß-pinene and other compounds that are stored in leaves. The measured isoprene emission factors were much higher than dynamic measurements. There were a large number of compounds to be detected by dynamic technique that could not be detected by the semi-static technique. But the semi-static technique could still provide qualitative information on categorization of non, low and high emitters for some compounds.

  28. 2018

  29. Hodshire AL, Palm BB, Alexander ML, Bian Q, Campuzano-Jost P, Cross ES, Day DA, de Sá SS, Guenther AB, Hansel A, Hunter JF, Jud W, Karl T, Kim S, Kroll JH, Park J-H, Peng Z, Seco R, Smith JN, Jimenez JL, Pierce JR (2018) Constraining nucleation, condensation, and chemistry in oxidation flow reactors using size-distribution measurements and aerosol microphysical modeling. Atmospheric Chemistry and Physics, 18: 12433-12460 Supplement Abstract

    Oxidation flow reactors (OFRs) allow the concentration of a given atmospheric oxidant to be increased beyond ambient levels in order to study secondary organic aerosol (SOA) formation and aging over varying periods of equivalent aging by that oxidant. Previous studies have used these reactors to determine the bulk OA mass and chemical evolution. To our knowledge, no OFR study has focused on the interpretation of the evolving aerosol size distributions. In this study, we use size-distribution measurements of the OFR and an aerosol microphysics model to learn about size-dependent processes in the OFR. Specifically, we use OFR exposures between 0.09 and 0.9 equivalent days of OH aging from the 2011 BEACHON-RoMBAS and GoAmazon2014/5 field campaigns. We use simulations in the TOMAS (TwO-Moment Aerosol Sectional) microphysics box model to constrain the following parameters in the OFR: (1) the rate constant of gas-phase functionalization reactions of organic compounds with OH, (2) the rate constant of gas-phase fragmentation reactions of organic compounds with OH, (3) the reactive uptake coefficient for heterogeneous fragmentation reactions with OH, (4) the nucleation rate constants for three different nucleation schemes, and (5) an effective accommodation coefficient that accounts for possible particle diffusion limitations of particles larger than 60 nm in diameter.

    We find the best model-to-measurement agreement when the accommodation coefficient of the larger particles (Dp>60 nm) was 0.1 or lower (with an accommodation coefficient of 1 for smaller particles), which suggests a diffusion limitation in the larger particles. When using these low accommodation-coefficient values, the model agrees with measurements when using a published H2SO4-organics nucleation mechanism and previously published values of rate constants for gas-phase oxidation reactions. Further, gas-phase fragmentation was found to have a significant impact upon the size distribution, and including fragmentation was necessary for accurately simulating the distributions in the OFR. The model was insensitive to the value of the reactive uptake coefficient on these aging timescales. Monoterpenes and isoprene could explain 24%–95% of the observed change in total volume of aerosol in the OFR, with ambient semivolatile and intermediate-volatility organic compounds (S/IVOCs) appearing to explain the remainder of the change in total volume. These results provide support to the mass-based findings of previous OFR studies, give insight to important size-distribution dynamics in the OFR, and enable the design of future OFR studies focused on new particle formation and/or microphysical processes.

  30. Kim S, Jeong D, Sanchez D, Wang M, Seco R, Blake D, Meinardi S, Barletta B, Hughes S, Jung J, Kim D, Lee G, Lee M, Ahn J, Lee S-D, Cho G, Sung M-Y, Lee Y-H, Park R (2018) The Controlling Factors of Photochemical Ozone Production in Seoul, South Korea. Aerosol and Air Quality Research, 18 (9): 2253-2261 Abstract

    • Ozone and its precursors observed during the MAPS-Seoul campaign are presented.
    • Organic peroxy radicals play an important role in ozone production.
    • OH reactivity analysis highlights VOCs as a limiting factor in ozone production.
    • A comprehensive observational dataset is the basis for an ozone reduction policy.
    We present the ambient ozone and relevant observed trace gas dataset in Seoul, South Korea during the Megacity Air Pollution Studies (MAPS)-Seoul field campaign in May to June of 2015 (MAPS-Seoul 2015). We observed two distinctive periods, one with higher and the other with lower daytime ozone levels despite of the mostly clear conditions for the both periods. The importance of peroxy radical contributions to excess ozone production is illustrated by the substantial differences in the Leighton constant (Φ) for the two periods. Moreover, higher levels of hydroxyl radical (OH) reactivity (s–1) were observed during the high ozone episode compared to the low ozone episode as much as ~5 s–1. Contributions of nitrogen oxides (NOx) to OH reactivity become less important compared to volatile organic compounds (VOCs) during the high ozone episode, which suggests the NOx saturated ozone production regime. It was also notable that isoprene biogenic VOC contributes most to OH reactivity contribution calculated among from observed VOCs in the afternoon consistently over the whole field campaign period. Finally, we ran multiple box model scenarios to evaluate the ozone production rates of three different air mixtures: high ozone, low ozone, and a simulated regional air quality model mixture. The results illustrate that the total OH reactivity levels and the relative contributions of VOCs to NOx play critical roles in ozone production rates. The simulated regional air quality air mixture results in lower OH reactivity causing lower ozone production rates than those calculated for the high ozone episode air mixture. This exercise clearly urges further improvements in the regional model system to accurately simulate ozone precursors in the regions. This study clearly suggests that a comprehensive trace gas dataset along with observed OH reactivity allows us to properly diagnose the photochemistry behind ozone pollution, leading to effective ozone abatement policy implantations.

  31. Filella I, Zhang C, Seco R, Potosnak M, Guenther A, Karl T, Gamon J, Pallardy S, Gu L, Kim S, Balzarolo M, Fernandez-Martinez M, Peñuelas J (2018) A MODIS photochemical reflectance index (PRI) as an estimator of isoprene emissions in a temperate deciduous forest. Remote Sensing, 10 (4): 557 Abstract

    The quantification of isoprene and monoterpene emissions at the ecosystem level with available models and field measurements is not entirely satisfactory. Remote-sensing techniques can extend the spatial and temporal assessment of isoprenoid fluxes. Detecting the exchange of biogenic volatile organic compounds (BVOCs) using these techniques is, however, a very challenging goal. Recent evidence suggests that a simple remotely sensed index, the photochemical reflectance index (PRI), which is indicative of light-use efficiency, relative pigment levels and excess reducing power, is a good indirect estimator of foliar isoprenoid emissions. We tested the ability of PRI to assess isoprenoid fluxes in a temperate deciduous forest in central USA throughout the entire growing season and under moderate and extreme drought conditions. We compared PRI time series calculated with MODIS bands to isoprene emissions measured with eddy covariance. MODIS PRI was correlated with isoprene emissions for most of the season, until emissions peaked. MODIS PRI was also able to detect the timing of the annual peak of emissions, even when it was advanced in response to drought conditions. PRI is thus a promising index to estimate isoprene emissions when it is complemented by information on potential emission. It may also be used to further improve models of isoprene emission under drought and other stress conditions. Direct estimation of isoprene emission by PRI is, however, limited, because PRI estimates LUE, and the relationship between LUE and isoprene emissions can be modified by severe stress conditions.

  32. Liu Y, Seco R, Kim S, Guenther AB, Goldstein AH, Keutsch FN, Springston SR, Watson TB, Artaxo P, Souza RAF, McKinney KA, Martin ST (2018) Isoprene photo-oxidation products quantify the effect of pollution on hydroxyl radicals over Amazonia. Science Advances, 4 (4): eaar2547 Supplement Abstract

    Nitrogen oxides (NOx) emitted from human activities are believed to regulate the atmospheric oxidation capacity of the troposphere. However, observational evidence is limited for the low-to-median NOx concentrations prevalent outside of polluted regions. Directly measuring oxidation capacity, represented primarily by hydroxyl radicals (OH), is challenging, and the span in NOx concentrations at a single observation site is often not wide. Concentrations of isoprene and its photo-oxidation products were used to infer the equivalent noontime OH concentrations. The fetch at an observation site in central Amazonia experienced varied contributions from background regional air, urban pollution, and biomass burning. The afternoon concentrations of reactive nitrogen oxides (NOy), indicative of NOx exposure during the preceding few hours, spanned from 0.3 to 3.5 parts per billion. Accompanying the increase of NOy concentration, the inferred equivalent noontime OH concentrations increased by at least 250% from 0.6 × 106 to 1.6 × 106 cm-3. The conclusion is that, compared to background conditions of low NOx concentrations over the Amazon forest, pollution increased NOx concentrations and amplified OH concentrations, indicating the susceptibility of the atmospheric oxidation capacity over the forest to anthropogenic influence and reinforcing the important role of NOx in sustaining OH concentrations.

  33. Jiang X, Guenther A, Potosnak M, Geron C, Seco R, Karl T, Kim S, Gu L, Pallardy S (2018) Isoprene emission response to drought and the impact on global atmospheric chemistry. Atmospheric Environment, 183: 69-83 Erratum (Fig. 8) Abstract

    • Severe droughts have significant impacts on biogenic isoprene emissions.
    • The new drought activity algorithm improves model simulation of biogenic isoprene under drought conditions.
    • Drought-induced changes in isoprene emissions change surface ozone and oxidants.
    Biogenic isoprene emissions play a very important role in atmospheric chemistry. These emissions are strongly dependent on various environmental conditions, such as temperature, solar radiation, plant water stress, ambient ozone and CO2 concentrations, and soil moisture. Current biogenic emission models (i.e., Model of Emissions of Gases and Aerosols from Nature, MEGAN) can simulate emission responses to some of the major driving variables, such as short-term variations in temperature and solar radiation, but the other factors are either missing or poorly represented. In this paper, we propose a new modeling approach that considers the physiological effects of drought stress on plant photosynthesis and isoprene emissions for use in the MEGAN3 biogenic emission model. We test the MEGAN3 approach by integrating the algorithm into the existing MEGAN2.1 biogenic emission model framework embedded into the global Community Land Model of the Community Earth System Model (CLM4.5/CESM1.2). Single-point simulations are compared against available field measurements at the Missouri Ozarks AmeriFlux (MOFLUX) field site. The modeling results show that the MEGAN3 approach of using of a photosynthesis parameter (Vcmax) and soil wetness factor (ßt) to determine the drought activity factor leads to better simulated isoprene emissions in non-drought and drought periods. The global simulation with the MEGAN3 approach predicts a 17% reduction in global annual isoprene emissions, in comparison to the value predicted using the default CLM4.5/MEGAN2.1 without any drought effect. This reduction leads to changes in surface ozone and oxidants in the areas where the reduction of isoprene emissions is observed. Based on the results presented in this study, we conclude that it is important to simulate the drought-induced response of biogenic isoprene emission accurately in the coupled Earth System model.

  34. Palm BB, de Sá SS, Day DA, Campuzano-Jost P, Hu W, Seco R, Sjostedt SJ, Park J-H, Guenther AB, Kim S, Brito J, Wurm F, Artaxo P, Thalman R, Wang J, Yee LD, Wernis R, Isaacman-VanWertz G, Goldstein AH, Liu Y, Springston SR, Souza R, Newburn MK, Alexander ML, Martin ST, Jimenez JL (2018) Secondary organic aerosol formation from ambient air in an oxidation flow reactor in central Amazonia. Atmospheric Chemistry and Physics, 18: 467-493 Supplement Abstract

    Secondary organic aerosol (SOA) formation from ambient air was studied using an oxidation flow reactor (OFR) coupled to an aerosol mass spectrometer (AMS) during both the wet and dry seasons at the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) field campaign. Measurements were made at two sites downwind of the city of Manaus, Brazil. Ambient air was oxidized in the OFR using variable concentrations of either OH or O3, over ranges from hours to days (O3) or weeks (OH) of equivalent atmospheric aging. The amount of SOA formed in the OFR ranged from 0 to as much as 10 µg m-3, depending on the amount of SOA precursor gases in ambient air. Typically, more SOA was formed during nighttime than daytime, and more from OH than from O3 oxidation. SOA yields of individual organic precursors under OFR conditions were measured by standard addition into ambient air and were confirmed to be consistent with published environmental chamber-derived SOA yields. Positive matrix factorization of organic aerosol (OA) after OH oxidation showed formation of typical oxidized OA factors and a loss of primary OA factors as OH aging increased. After OH oxidation in the OFR, the hygroscopicity of the OA increased with increasing elemental O:C up to O:C ~ 1.0, and then decreased as O:C increased further. Possible reasons for this decrease are discussed. The measured SOA formation was compared to the amount predicted from the concentrations of measured ambient SOA precursors and their SOA yields. While measured ambient precursors were sufficient to explain the amount of SOA formed from O3, they could only explain 10–50 % of the SOA formed from OH. This is consistent with previous OFR studies, which showed that typically unmeasured semivolatile and intermediate volatility gases (that tend to lack C=C bonds) are present in ambient air and can explain such additional SOA formation. To investigate the sources of the unmeasured SOA-forming gases during this campaign, multilinear regression analysis was performed between measured SOA formation and the concentration of gas-phase tracers representing different precursor sources. The majority of SOA-forming gases present during both seasons were of biogenic origin. Urban sources also contributed substantially in both seasons, while biomass burning sources were more important during the dry season. This study enables a better understanding of SOA formation in environments with diverse emission sources.

      Listed Highly Cited Article as of July/August 2019 (top 1% of the field of Geosciences; WebofScience Essential Science Indicators, Clarivate Analytics)
  35. Sanchez D, Jeong D, Seco R, Wrangham I, Park J-H, Brune WH, Koss A, Gilman J, de Gouw J, Misztal P, Goldstein A, Baumann K, Wennberg PO, Keutsch FN, Guenther A, Kim S (2018) Intercomparison of OH concentrations and OH reactivity measurements in a high isoprene and low NO environment during the Southern Oxidants and Aerosol Study (SOAS). Atmospheric Environment, 174: 227-236 Supplement Abstract

    We intercompare OH and OH reactivity datasets from two different techniques, chemical ionization mass spectrometry (CIMS) and laser-induced fluorescence (LIF) in a high isoprene and low NO environment in a southeastern US forest during the Southern Oxidant and Aerosol Study (SOAS). An LIF instrument measured OH and OH reactivity at the top of a tower, a CIMS instrument measured OH at the top of the tower, and a CIMS based comparative reactivity method (CRM-CIMS) instrument deployed at the base of the tower measured OH reactivity. Averaged diel variations of OH and OH reactivity from these datasets agree within analytical uncertainty and correlations of LIF versus CIMS for OH and OH reactivity have slopes of 0.65 and 0.97, respectively. However, there are systematic differences between the measurement datasets. The CRM-CIMS measurements of OH reactivity were ~16% lower than those by the LIF technique in the late afternoon. We speculate that it is caused by losses in the sampling line down to the CRM-CIMS instrument. On the other hand, we could not come up with a reasonable explanation for the difference in the LIF and CIMS OH datasets for early morning and late afternoon when OH is below 1 × 106 molecules cm-3. Nonetheless, results of this intercomparison exercise strengthen previous publications from the field site on OH concentrations and atmospheric reactivity.

  36. 2017

  37. Zheng Y, Unger N, Tadic JM, Seco R, Guenther AB, Barkley MP, Potosnak MJ, Murray L, Michalak AM, Qiu X, Kim S, Karl T, Gu L, Pallardy SG (2017) Drought impacts on photosynthesis, isoprene emission and atmospheric formaldehyde in a mid-latitude forest. Atmospheric Environment, 167: 190-201 Abstract

    • Satellite SIF response to severe 2012 drought muted relative to flux tower GPP.
    • Satellite HCHO column response to 2012 drought muted relative to isoprene emission.
    • Satellite SIF and surface isoprene emission show strong correlation on monthly scales.
    Isoprene plays a critical role in air quality and climate. Photosynthesis (gross primary productivity, GPP) and formaldehyde (HCHO) are both related to isoprene emission at large spatiotemporal scales, but neither is a perfect proxy. We apply multiple satellite products and site-level measurements to examine the impact of water deficit on the three interlinked variables at the Missouri Ozarks site during a 20-day mild dryness stress in summer 2011 and a 3-month severe drought in summer 2012. Isoprene emission shows opposite responses to the short- and long-term droughts, while GPP was substantially reduced in both cases. In 2012, both remote-sensed solar-induced fluorescence (SIF) and satellite HCHO column qualitatively capture reductions in flux-derived GPP and isoprene emission, respectively, on weekly to monthly time scales, but with muted responses. For instance, as flux-derived GPP approaches zero in late summer 2012, SIF drops by 29–33% (July) and 19–27% (August) relative to year 2011. A possible explanation is that electron transport and photosystem activity are maintained to a certain extent under the drought stress. Similarly, flux tower isoprene emissions in July 2012 are 54% lower than July 2011, while the relative reductions in July for 3 independent satellite-derived HCHO data products are 27%, 12% and 6%, respectively. We attribute the muted HCHO response to a photochemical feedback whereby reduced isoprene emission increases the oxidation capacity available to generate HCHO from other volatile organic compound sources. Satellite SIF offers a potential alternative indirect method to monitor isoprene variability at large spatiotemporal scales from space, although further research is needed under different environmental conditions and regions. Our analysis indicates that fairly moderate reductions in satellite SIF and HCHO column may imply severe drought conditions at the surface.

  38. Gu D, Guenther AB, Shilling JE, Yu H, Huang M, Zhao C, Yang Q, Martin ST, Artaxo P, Kim S, Seco R, Stavrakou T, Longo KM, Tóta J, Souza RAF, Vega O, Liu Y, Shrivastava M, Alves EG, Santos FC, Leng G, Hu Z (2017) Airborne observations reveal elevational gradient in tropical forest isoprene emissions. Nature Communications, 8: 15541 Supplement Abstract

    Isoprene dominates global non-methane volatile organic compound emissions, and impacts tropospheric chemistry by influencing oxidants and aerosols. Isoprene emission rates vary over several orders of magnitude for different plants, and characterizing this immense biological chemodiversity is a challenge for estimating isoprene emission from tropical forests. Here we present the isoprene emission estimates from aircraft eddy covariance measurements over the Amazonian forest. We report isoprene emission rates that are three times higher than satellite top-down estimates and 35% higher than model predictions. The results reveal strong correlations between observed isoprene emission rates and terrain elevations, which are confirmed by similar correlations between satellite-derived isoprene emissions and terrain elevations. We propose that the elevational gradient in the Amazonian forest isoprene emission capacity is determined by plant species distributions and can substantially explain isoprene emission variability in tropical forests, and use a model to demonstrate the resulting impacts on regional air quality.

  39. Seco R, Karl T, Turnipseed A, Greenberg J, Guenther A, Llusia J, Peñuelas J, Dicken U, Rotenberg E, Kim S, Yakir D (2017) Springtime ecosystem-scale monoterpene fluxes from Mediterranean pine forests across a precipitation gradient. Agricultural and Forest Meteorology, 237: 150-159 Abstract

    • We quantified monoterpene (MT) fluxes in two pine forests across a rainfall gradient.
    • The drier site suffered a heat wave that lowered net daytime CO2 assimilation.
    • Both forests showed similar daytime standardized MT emission capacities.
    • Emission models overestimated MT fluxes under high temperatures of a heat wave.
    • Interaction of drought and high temperatures drives biogenic MT emissions.
    We quantified springtime ecosystem-scale monoterpene fluxes from two similar Aleppo pine (Pinus halepensis Mill.) forests, located in Israel, that differed in the amount of received precipitation: Yatir in the arid south and Birya in the northern part of Israel (291 and 755 mm annual average rainfall, respectively). In addition to the lower water availability, during our measurement campaign the Yatir site suffered from a heat wave with temperatures up to 35 ºC, which made the campaign-average net CO2 assimilation to occur in the morning (1 µmol m-2 s-1), with the rest of the daytime hours mainly dominated by net release of CO2. The milder conditions at Birya favored a higher net CO2 assimilation during all daytime hours (with average peaks higher than 10 µmol m-2 s-1). Despite these large differences in ambient conditions and CO2 net assimilation, daytime monoterpene emission capacities at both sites were comparable. While observed monoterpene fluxes were lower at Yatir than at Birya (hourly averages up to 0.4 and 1 mg m-2 h-1, respectively), the standardized hourly fluxes, after accounting for the differences in light, temperature and stand density between both sites, were comparable (0-1.3 mg m-2 h-1). The approach typically used by biogenic emission models overestimated monoterpene fluxes at Yatir when temperatures rose during the heat wave. This result, together with complementary leaf-level measurements showing that summertime monoterpene fluxes almost completely ceased at Yatir while being enhanced at Birya, highlight the interaction of water scarcity and high temperatures that drive monoterpene emissions from vegetation in such extreme climate zones and the need to further improve model performance.

  40. 2016

  41. Hu W, Palm BB, Day DA, Campuzano-Jost P, Krechmer JE, Peng Z, de Sá SS, Martin ST, Alexander ML, Baumann K, Hacker L, Kiendler-Scharr A, Koss AR, de Gouw JA, Goldstein AH, Seco R, Sjostedt SJ, Park J-H, Guenther AB, Kim S, Canonaco F, Prévôt ASH, Brune WH, Jimenez JL (2016) Volatility and lifetime against OH heterogeneous reaction of ambient isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA). Atmospheric Chemistry and Physics, 16: 11563-11580 Supplement Abstract

    Isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA) can contribute substantially to organic aerosol (OA) concentrations in forested areas under low NO conditions, hence significantly influencing the regional and global OA budgets, accounting, for example, for 16–36 % of the submicron OA in the southeastern United States (SE US) summer. Particle evaporation measurements from a thermodenuder show that the volatility of ambient IEPOX-SOA is lower than that of bulk OA and also much lower than that of known monomer IEPOX-SOA tracer species, indicating that IEPOX-SOA likely exists mostly as oligomers in the aerosol phase. The OH aging process of ambient IEPOX-SOA was investigated with an oxidation flow reactor (OFR). New IEPOX-SOA formation in the reactor was negligible, as the OFR does not accelerate processes such as aerosol uptake and reactions that do not scale with OH. Simulation results indicate that adding ~ 100 µg m-3 of pure H2SO4 to the ambient air allows IEPOX-SOA to be efficiently formed in the reactor. The heterogeneous reaction rate coefficient of ambient IEPOX-SOA with OH radical (kOH) was estimated as 4.0 ± 2.0 × 10-13 cm3 molec-1 s-1, which is equivalent to more than a 2-week lifetime. A similar kOH was found for measurements of OH oxidation of ambient Amazon forest air in an OFR. At higher OH exposures in the reactor (> 1 × 1012 molec cm-3 s), the mass loss of IEPOX-SOA due to heterogeneous reaction was mainly due to revolatilization of fragmented reaction products. We report, for the first time, OH reactive uptake coefficients (γOH = 0.59 ± 0.33 in SE US and γOH = 0.68 ± 0.38 in Amazon) for SOA under ambient conditions. A relative humidity dependence of kOH and γOH was observed, consistent with surface-area-limited OH uptake. No decrease of kOH was observed as OH concentrations increased. These observations of physicochemical properties of IEPOX-SOA can help to constrain OA impact on air quality and climate.

  42. Kourtchev I, Godoi RHM, Connors S, Levine JG, Archibald AT, Godoi AFL, Paralovo SL, Barbosa CGG, Souza RAF, Manzi AO, Seco R, Sjostedt S, Park J-H, Guenther A, Kim S, Smith J, Martin ST, Kalberer M (2016) Molecular composition of organic aerosols in central Amazonia: an ultra-high-resolution mass spectrometry study. Atmospheric Chemistry and Physics, 16: 11899-11913 Supplement Abstract

    The Amazon Basin plays key role in atmospheric chemistry, biodiversity and climate change. In this study we applied nanoelectrospray (nanoESI) ultra-high-resolution mass spectrometry (UHRMS) for the analysis of the organic fraction of PM2.5 aerosol samples collected during dry and wet seasons at a site in central Amazonia receiving background air masses, biomass burning and urban pollution. Comprehensive mass spectral data evaluation methods (e.g. Kendrick mass defect, Van Krevelen diagrams, carbon oxidation state and aromaticity equivalent) were used to identify compound classes and mass distributions of the detected species. Nitrogen- and/or sulfur-containing organic species contributed up to 60 % of the total identified number of formulae. A large number of molecular formulae in organic aerosol (OA) were attributed to later-generation nitrogen- and sulfur-containing oxidation products, suggesting that OA composition is affected by biomass burning and other, potentially anthropogenic, sources. Isoprene-derived organosulfate (IEPOX-OS) was found to be the most dominant ion in most of the analysed samples and strongly followed the concentration trends of the gas-phase anthropogenic tracers confirming its mixed anthropogenic–biogenic origin. The presence of oxidised aromatic and nitro-aromatic compounds in the samples suggested a strong influence from biomass burning especially during the dry period. Aerosol samples from the dry period and under enhanced biomass burning conditions contained a large number of molecules with high carbon oxidation state and an increased number of aromatic compounds compared to that from the wet period. The results of this work demonstrate that the studied site is influenced not only by biogenic emissions from the forest but also by biomass burning and potentially other anthropogenic emissions from the neighbouring urban environments.

  43. Kravitz B, Guenther AB, Gu L, Karl T, Kaser L, Pallardy SG, Peñuelas J, Potosnak MJ, Seco R (2016) A new paradigm of quantifying ecosystem stress through chemical signatures. Ecosphere, 7(11): e01559 Abstract

    Stress-induced emissions of biogenic volatile organic compounds (VOCs) from terrestrial ecosystems may be one of the dominant sources of VOC emissions worldwide. Understanding the ecosystem stress response could reveal how ecosystems will respond and adapt to climate change and, in turn, quantify changes in the atmospheric burden of VOC oxidants and secondary organic aerosols. Here, we argue, based on preliminary evidence from several opportunistic measurement sources, that chemical signatures of stress can be identified and quantified at the ecosystem scale. We also outline future endeavors that we see as next steps toward uncovering quantitative signatures of stress, including new advances in both VOC data collection and analysis of “big data”.

  44. Liu Y, Brito J, Dorris M, Rivera-Rios JC, Seco R, Bates KH, Artaxo P, Duvoisin Junior S, Keutsch FN, Kim S, Goldstein AH, Guenther A, Manzi AO, de Souza R, Springston SR, Watson TB, McKinney KA, Martin ST (2016) Isoprene photochemistry over the Amazon rainforest. Proceedings of the National Academy of Sciences of the USA, 113: 6125-6130 +SI SI Dataset Abstract

    Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4–0.6. This result implies a ratio of the reaction rate of ISOPOO with HO2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.

  45. Young DE, Kim H, Parworth C, Zhou S, Zhang X, Cappa CD, Seco R, Kim S, Zhang Q (2016) Influences of emission sources and meteorology on aerosol chemistry in a polluted urban environment: results from DISCOVER-AQ California. Atmospheric Chemistry and Physics, 16: 5427-5451 Supplement Abstract

    The San Joaquin Valley (SJV) in California experiences persistent air-quality problems associated with elevated particulate matter (PM) concentrations due to anthropogenic emissions, topography, and meteorological conditions. Thus it is important to unravel the various sources and processes that affect the physicochemical properties of PM in order to better inform pollution abatement strategies and improve parameterizations in air-quality models.

    During January and February 2013, a ground supersite was installed at the Fresno–Garland California Air Resources Board (CARB) monitoring station, where comprehensive, real-time measurements of PM and trace gases were performed using instruments including an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and an Ionicon proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) as part of the NASA Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) campaign. The average submicron aerosol (PM1) concentration was 31.0 μg m−3 and the total mass was dominated by organic aerosols (OA, 55 %), followed by ammonium nitrate (35 %). High PM pollution events were commonly associated with elevated OA concentrations, mostly from primary sources. Organic aerosols had average atomic oxygen-to-carbon (O / C), hydrogen-to-carbon (H / C), and nitrogen-to-carbon (N / C) ratios of 0.42, 1.70, and 0.017, respectively. Six distinct sources of organic aerosol were identified from positive matrix factorization (PMF) analysis of the AMS data: hydrocarbon-like OA (HOA; 9 % of total OA, O / C = 0.09) associated with local traffic, cooking OA (COA; 18 % of total OA, O / C = 0.19) associated with food cooking activities, two biomass burning OA (BBOA1: 13 % of total OA, O / C = 0.33; BBOA2: 20 % of total OA, O / C = 0.60) most likely associated with residential space heating from wood combustion, and semivolatile oxygenated OA (SV-OOA; 16 % of total OA, O / C = 0.63) and low-volatility oxygenated OA (LV-OOA; 24 % of total OA, O / C = 0.90) formed via chemical reactions in the atmosphere.

    Large differences in aerosol chemistry at Fresno were observed between the current campaign (winter 2013) and a previous campaign in winter 2010, most notably that PM1 concentrations were nearly 3 times higher in 2013 than in 2010. These variations were attributed to differences in the meteorological conditions, which influenced primary emissions and secondary aerosol formation. In particular, COA and BBOA concentrations were greater in 2013 than 2010, where colder temperatures in 2013 likely resulted in increased biomass burning activities. The influence from a nighttime formed residual layer that mixed down in the morning was found to be much more intense in 2013 than 2010, leading to sharp increases in ground-level concentrations of secondary aerosol species including nitrate, sulfate, and OOA, in the morning between 08:00 and 12:00 PST. This is an indication that nighttime chemical reactions may have played a more important role in 2013. As solar radiation was stronger in 2013 the higher nitrate and OOA concentrations in 2013 could also be partly due to greater photochemical production of secondary aerosol species. The greater solar radiation and larger range in temperature in 2013 also likely led to both SV-OOA and LV-OOA being observed in 2013 whereas only a single OOA factor was identified in 2010.

  46. Kim S, Sanchez D, Wang MD, Seco R, Jeong D, Hughes S, Barletta B, Blake DR, Jung J, Kim D, Lee G, Lee M, Ahn J, Lee S-D, Cho G, Sung M-Y, Lee Y-H, Kim DB, Kim Y, Woo J-H, Jo D, Park R, Park J-H, Hong Y-D, Hong J-H (2016) OH Reactivity in Urban and Suburban regions in Seoul, South Korea - An East Asian megacity in a rapid transition. Faraday Discussions, 189: 231-251 Abstract

    South Korea has recently achieved developed country status with the second largest megacity in the world, the Seoul Metropolitan Area (SMA). This study provides insights into future changes in air quality for rapidly emerging megacities in the East Asian region. We present total OH reactivity observations in the SMA conducted at an urban Seoul site (May–June, 2015) and a suburban forest site (Sep, 2015). The total OH reactivity in an urban site during the daytime was observed at similar levels (~15 s-1) to those previously reported from other East Asian megacity studies. Trace gas observations indicate that OH reactivity is largely accounted for by NOX (~50%) followed by volatile organic compounds (VOCs) (~35%). Isoprene accounts for a substantial fraction of OH reactivity among the comprehensive VOC observational dataset (25–47%). In general, observed total OH reactivity can be accounted for by the observed trace gas dataset. However, observed total OH reactivity in the suburban forest area cannot be largely accounted for (~70%) by the trace gas measurements. The importance of biogenic VOC (BVOCs) emissions and oxidations used to evaluate the impacts of East Asian megacity outflows for the regional air quality and climate contexts are highlighted in this study.

  47. Lee BH, Mohr C, Lopez-Hilfiker FD, Lutz A, Hallquist M, Lee L, Romer P, Cohen RC, Iyer S, Kurten T, Hu WW, Day DA, Campuzano-Jost P, Jimenez JL, Xu L, Ng NL, Guo H, Weber RJ, Wild RJ, Brown SS, Koss A, de Gouw J, Olson K, Goldstein AH, Seco R, Kim S, McAvey K, Shepson PB, Starn T, Baumann K, Edgerton ES, Liu J, Shilling JE, Miller DO, Brune WH, Schobesberger S, D'Ambro EL, Thornton JA (2016) Highly functionalized organic nitrates in the Southeast United States: contribution to secondary organic aerosol and reactive nitrogen budgets. Proceedings of the National Academy of Sciences of the USA, 113: 1516-1521 +SI Abstract

    Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization mass spectrometry during June and July of 2013 in rural Alabama as part of the Southern Oxidant and Aerosol Study. A large fraction of pON are highly functionalized, possessing between six and eight oxygen atoms within each carbon number group, and is not the common first-generation alkyl nitrates previously reported. Using calibrations for isoprene hydroxynitrates and the measured molecular compositions, we estimate that pON account for 3% and 8% of total submicrometer organic aerosol mass, on average, during the day and night, respectively. Each of the isoprene- and monoterpenes-derived groups exhibited a strong diel trend consistent with the emission patterns of likely biogenic hydrocarbon precursors. An observationally constrained diel box model can replicate the observed pON assuming that pONs i) are produced in the gas phase and rapidly establish gas-particle equilibrium and ii) have a short particle-phase lifetime (2-4 h). Such dynamic behavior has significant implications for the production and phase partitioning of pONs, organic aerosol mass, and reactive nitrogen speciation in a forested environment.

      Listed Highly Cited Article as of January/February 2017 (top 1% of the field of Geosciences; WebofScience Essential Science Indicators, Clarivate Analytics)
  48. Llusia J, Roahtyn S, Yakir D, Rotenberg E, Seco R, Guenther A, Peñuelas J (2016) Photosynthesis, stomatal conductance and terpene emission response to water availability in dry and mesic Mediterranean forests. Trees - Structure and Function, 30: 749-759 Abstract

    • Warmer summer conditions result in increased terpene emissions except under severe drought, in which case they strongly decrease.
    Water stress results in a reduction of the metabolism of plants and in a reorganization of their use of resources geared to survival. In the Mediterranean region, periods of drought accompanied by high temperatures and high irradiance occur in summer. Plants have developed various mechanisms to survive in these conditions by resisting, tolerating or preventing stress. We used three typical Mediterranean tree species in Israel, Pinus halepensis L., Quercus calliprinos and Quercus ithaburensis Webb, as models for studying some of these adaptive mechanisms. We measured their photosynthetic rates (A), stomatal conductance (gs), and terpene emission rates during spring and summer in a geophysical gradient from extremely dry to mesic from Yatir (south, arid) to Birya (north, moist) with intermediate conditions in Solelim. A and gs of P. halepensis were threefold higher in Birya than in Yatir where they remained very low both seasons. Quercus species presented 2–3-fold higher A and gs but with much more variability between seasons, especially for Q. ithaburensis with A and gs that decreased 10–30-fold from spring to summer. Terpene emission rates for pine were not different regionally in spring but they were 5–8-fold higher in Birya than in Yatir in summer (P < 0.05). Higher emissions were also observed in Solelim for the drought resistant Q. ithaburensis (P < 0.001) but not for Q. calliprinos. α-Pinene followed by limonene and 3-carene were the dominant terpenes. Warmer summer conditions result in increased terpene emission rates except under severe drought, in which case they strongly decrease.

  49. Geron C, Daly R, Harley P, Rasmussen R, Seco R, Guenther A, Karl T, Gu L (2016) Large drought-induced variations in oak leaf volatile organic compound emissions during PINOT NOIR 2012. Chemosphere, 146: 8-21 Abstract

    • Leaf level Isoprene emission factors for 4 of 5 oaks were significantly reduced during a severe drought.
    • Quercus stellata leaf isoprene increased during the drought period.
    • Leaf isoprene response to increasing temperature was impacted for most oak species.
    • The leaf BVOC emission data supports findings at the canopy level, but discrepancies for monoterpene emissions remain.
    Leaf-level isoprene and monoterpene emissions were collected and analyzed from five of the most abundant oak (Quercus) species in Central Missouri's Ozarks Region in 2012 during PINOT NOIR (Particle Investigations at a Northern Ozarks Tower – NOx, Oxidants, Isoprene Research). June measurements, prior to the onset of severe drought, showed isoprene emission rates and leaf temperature responses similar to those previously reported in the literature and used in Biogenic Volatile Organic Compound (BVOC) emission models. During the peak of the drought in August, isoprene emission rates were substantially reduced, and response to temperature was dramatically altered, especially for the species in the red oak subgenus (Erythrobalanus). Quercus stellata (in the white oak subgenus Leucobalanus), on the other hand, increased its isoprene emission rate during August, and showed no decline at high temperatures during June or August, consistent with its high tolerance to drought and adaptation to xeric sites at the prairie-deciduous forest interface. Mid-late October measurements were conducted after soil moisture recharge, but were affected by senescence and cooler temperatures. Isoprene emission rates were considerably lower from all species compared to June and August data. The large differences between the oaks in response to drought emphasizes the need to consider BVOC emissions at the species level instead of just the whole canopy. Monoterpene emissions from Quercus rubra in limited data were highest among the oaks studied, while monoterpene emissions from the other oak species were 80–95% lower and less than assumed in current BVOC emission models. Major monoterpenes from Q. rubra (and in ambient air) were p-cymene, α-pinene, ß-pinene, D-limonene, γ-terpinene, ß-ocimene (predominantly1,3,7-trans-ß-ocimene, but also 1,3,6-trans-ß-ocimene), tricyclene, α-terpinene, sabinene, terpinolene, and myrcene. Results are discussed in the context of canopy flux studies conducted at the site during PINOT NOIR, which are described elsewhere. The leaf isoprene emissions before and during the drought were consistent with above canopy fluxes, while leaf and branch monoterpene emissions were an order of magnitude lower than the observed above canopy fluxes, implying that other sources may be contributing substantially to monoterpene fluxes at this site. This strongly demonstrates the need for further simultaneous canopy and enclosure BVOC emission studies.

  50. 2015

  51. Wohlfahrt G, Amelynck C, Ammann C, Arneth A, Bamberger I, Goldstein AH, Gu L, Guenther A, Hansel A, Heinesch B, Holst T, Hörtnagl L, Karl T, Laffineur Q, Neftel A, McKinney K, Munger JW, Pallardy SG, Schade GW, Seco R, Schoon N (2015) An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements. Atmospheric Chemistry and Physics, 15: 7413-7427 Supplement Abstract

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates, reflecting uncertainties in the approaches used to model and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land–atmosphere methanol exchange. Our study shows that the controls of plant growth on production, and thus the methanol emission magnitude, as well as stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; however, they are neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow for full advantage to be taken of the rich information content of micrometeorological flux measurements.

  52. Seco R, Karl T, Guenther A, Hosman K, Pallardy S, Gu L, Geron C, Harley P, Kim S (2015) Ecosystem-scale volatile organic compound fluxes during an extreme drought in a broadleaf temperate forest of the Missouri Ozarks (central USA). Global Change Biology, 21: 3657–3674 Supplement Abstract

    Considerable amounts and varieties of biogenic volatile organic compounds (BVOCs) are exchanged between vegetation and the surrounding air. These BVOCs play key ecological and atmospheric roles that must be adequately represented for accurately modeling the coupled biosphere-atmosphere-climate earth system. One key uncertainty in existing models is the response of BVOC fluxes to an important global change process: drought. We describe the diurnal and seasonal variation in isoprene, monoterpene and methanol fluxes from a temperate forest ecosystem before, during, and after an extreme 2012 drought event in the Ozark region of the central USA. BVOC fluxes were dominated by isoprene, which attained high emission rates of up to 35.4 mg m-2 h-1 at midday. Methanol fluxes were characterized by net deposition in the morning, changing to a net emission flux through the rest of the daylight hours. Net flux of CO2 reached its seasonal maximum approximately a month earlier than isoprenoid fluxes, which highlights the differential response of photosynthesis and isoprenoid emissions to progressing drought conditions. Nevertheless, both processes were strongly suppressed under extreme drought, although isoprene fluxes remained relatively high compared to reported fluxes from other ecosystems. Methanol exchange was less affected by drought throughout the season, confirming the complex processes driving biogenic methanol fluxes. The fraction of daytime (7-17 h) assimilated carbon released back to the atmosphere combining the three BVOCs measured was 2% of gross primary productivity (GPP) and 4.9% of net ecosystem exchange (NEE) on average for our whole measurement campaign, while exceeding 5% of GPP and 10% of NEE just before the strongest drought phase. The MEGANv2.1 model correctly predicted diurnal variations in fluxes driven mainly by light and temperature, although further research is needed to address model BVOC fluxes during drought events.

  53. Thalman R, Baeza-Romero MT, Ball SM, Borrás E, Daniels MJS, Goodall ICA, Henry SB, Karl T, Keutsch FN, Kim S, Mak J, Monks PS, Muñoz A, Orlando J, Peppe S, Rickard AR, Ródenas M, Sánchez P, Seco R, Su L, Tyndall G, Vázquez M, Vera T, Waxman E, Volkamer R (2015) Instrument inter-comparison of glyoxal, methyl glyoxal and NO2 under simulated atmospheric conditions. Atmospheric Measurement Techniques, 8: 1835-1862 Supplement Abstract

    The α-dicarbonyl compounds glyoxal (CHOCHO) and methyl glyoxal (CH3C(O)CHO) are produced in the atmosphere by the oxidation of hydrocarbons and emitted directly from pyrogenic sources. Measurements of ambient concentrations inform about the rate of hydrocarbon oxidation, oxidative capacity, and secondary organic aerosol (SOA) formation. We present results from a comprehensive instrument comparison effort at two simulation chamber facilities in the US and Europe that included nine instruments, and seven different measurement techniques: broadband cavity enhanced absorption spectroscopy (BBCEAS), cavity-enhanced differential optical absorption spectroscopy (CE-DOAS), white-cell DOAS, Fourier transform infrared spectroscopy (FTIR, two separate instruments), laser-induced phosphorescence (LIP), solid-phase micro extraction (SPME), and proton transfer reaction mass spectrometry (PTR-ToF-MS, two separate instruments; for methyl glyoxal only because no significant response was observed for glyoxal). Experiments at the National Center for Atmospheric Research (NCAR) compare three independent sources of calibration as a function of temperature (293–330 K). Calibrations from absorption cross-section spectra at UV-visible and IR wavelengths are found to agree within 2% for glyoxal, and 4% for methyl glyoxal at all temperatures; further calibrations based on ion–molecule rate constant calculations agreed within 5% for methyl glyoxal at all temperatures. At the European Photoreactor (EUPHORE) all measurements are calibrated from the same UV-visible spectra (either directly or indirectly), thus minimizing potential systematic bias. We find excellent linearity under idealized conditions (pure glyoxal or methyl glyoxal, R2 > 0.96), and in complex gas mixtures characteristic of dry photochemical smog systems (o-xylene/NOx and isoprene/NOx, R2 > 0.95; R2 ~ 0.65 for offline SPME measurements of methyl glyoxal). The correlations are more variable in humid ambient air mixtures (RH > 45%) for methyl glyoxal (0.58 < R2 < 0.68) than for glyoxal (0.79 < R2 < 0.99). The intercepts of correlations were insignificant for the most part (below the instruments' experimentally determined detection limits); slopes further varied by less than 5% for instruments that could also simultaneously measure NO2. For glyoxal and methyl glyoxal the slopes varied by less than 12 and 17% (both 3-σ) between direct absorption techniques (i.e., calibration from knowledge of the absorption cross section). We find a larger variability among in situ techniques that employ external calibration sources (75–90%, 3-σ), and/or techniques that employ offline analysis. Our intercomparison reveals existing differences in reports about precision and detection limits in the literature, and enables comparison on a common basis by observing a common air mass. Finally, we evaluate the influence of interfering species (e.g., NO2, O3 and H2O) of relevance in field and laboratory applications. Techniques now exist to conduct fast and accurate measurements of glyoxal at ambient concentrations, and methyl glyoxal under simulated conditions. However, techniques to measure methyl glyoxal at ambient concentrations remain a challenge, and would be desirable.

  54. 2014

  55. Yu H, Ortega J, Smith JN, Guenther AB, Kanawade VP, You Y, Liu Y, Hosman K, Karl T, Seco R, Geron C, Pallardy SG, Gu L, Mikkilä J, Lee S-H (2014) New particle formation and growth in an isoprene-dominated Ozark forest: from sub-5 nm to CCN-active sizes. Aerosol Science and Technology, 48: 1285-1298 Abstract

    Particle Investigations at a Northern Ozarks Tower: NOx, Oxidant, Isoprene Research (PINOT-NOIR) were conducted in a Missouri forest dominated by isoprene emissions from May to October 2012. This study presents results of new particle formation (NPF) and the growth of new particles to cloud condensation nuclei (CCN)-active sizes (~100 nm) observed during this field campaign. The measured sub-5 nm particles were up to ~20000 cm-3 during a typical NPF event. Nucleation rates J1 were relatively high (11.0±10.6 cm-3 s-1), and one order of magnitude higher than formation rates of 5 nm particles (J5). Sub-5 nm particle formation events were observed during 64% of measurement days, with a high preference in biogenic volatile organic compounds (BVOCs)- and SO2-poor northwesterly (90%) air masses than in BVOCs-rich southerly air masses (13%). About 80% of sub-5 nm particle events led to the further growth. While high temperatures and high aerosol loadings in the southerly air masses were not favorable for nucleation, high BVOCs in the southerly air masses facilitated the growth of new particles to CCN-active sizes. In overall, 0.4-9.4% of the sub-5 nm particles grew to CCN-active sizes within each single NPF event. During a regional NPF event period that took place consecutively over several days, concentrations of CCN size particles increased by a factor of 4.7 in average. This enhanced production of CCN particles from new particles was commonly observed during all 13 regional NPF events during the campaign period.

  56. Greenberg JP, Peñuelas J, Guenther A, Seco R, Turnipseed A, Jiang X, Filella I, Estiarte M, Sardans J, Ogaya R, Llusia J, Rapparini F (2014) A tethered-balloon PTRMS sampling approach for surveying of landscape-scale biogenic VOC fluxes. Atmospheric Measurement Techniques, 7: 2263-2271 Abstract

    Landscape-scale fluxes of biogenic gases were surveyed by deploying a 100 m Teflon tube attached to a tethered balloon as a sampling inlet for a fast-response proton-transfer-reaction mass spectrometer (PTRMS). Along with meteorological instruments deployed on the tethered balloon and a 3 m tripod and outputs from a regional weather model, these observations were used to estimate landscape-scale biogenic volatile organic compound fluxes with two micrometeorological techniques: mixed layer variance and surface layer gradients. This highly mobile sampling system was deployed at four field sites near Barcelona to estimate landscape-scale biogenic volatile organic compound (BVOC) emission factors in a relatively short period (3 weeks).

    The two micrometeorological techniques were compared with emissions predicted with a biogenic emission model using site-specific emission factors and land-cover characteristics for all four sites. The methods agreed within the uncertainty of the techniques in most cases, even though the locations had considerable heterogeneity in species distribution and complex terrain. Considering the wide range in reported BVOC emission factors for individual vegetation species (more than an order of magnitude), this temporally short and inexpensive flux estimation technique may be useful for constraining BVOC emission factors used as model inputs.

  57. Pandolfi M, Querol X, Alastuey A, Jimenez JL, Jorba O, Day DA, Ortega A, Cubison MJ, Comerón A, Sicard M, Mohr C, Prévôt ASH, Minguillón MC, Pey J, Baldasano JM, Burkhart JF, Seco R, Peñuelas J, van Drooge BL, Artiñano B, Di Marco C, Nemitz E, Schallhart S, Metzger A, Hansel A, Lorente J, Ng S, Jayne J, Szidat S (2014) Effects of Sources and Meteorology on Particulate Matter in the Western Mediterranean Basin: An overview of the DAURE campaign. Journal of Geophysical Research: Atmospheres, 119 (8): 4978–5010 Supplement Abstract

    DAURE (Determination of the Sources of Atmospheric Aerosols in Urban and Rural Environments in the Western Mediterranean) was a multidisciplinary international field campaign aimed at investigating the sources and meteorological controls of particulate matter in the Western Mediterranean Basin (WMB). Measurements were simultaneously performed at an urban-coastal (Barcelona, BCN) and a rural-elevated (Montseny, MSY) site pair in NE Spain during winter and summer. State-of-the-art methods such as 14C analysis, proton-transfer reaction mass spectrometry, and high-resolution aerosol mass spectrometry were applied for the first time in the WMB as part of DAURE. WMB regional pollution episodes were associated with high concentrations of inorganic and organic species formed during the transport to inland areas and built up at regional scales. Winter pollutants accumulation depended on the degree of regional stagnation of an air mass under anticyclonic conditions and the planetary boundary layer height. In summer, regional recirculation and biogenic secondary organic aerosols (SOA) formation mainly determined the regional pollutant concentrations. The contribution from fossil sources to organic carbon (OC) and elemental carbon (EC) and hydrocarbon-like organic aerosol concentrations were higher at BCN compared with MSY due to traffic emissions. The relative contribution of nonfossil OC was higher at MSY especially in summer due to biogenic emissions. The fossil OC/EC ratio at MSY was twice the corresponding ratio at BCN indicating that a substantial fraction of fossil OC was due to fossil SOA. In winter, BCN cooking emissions were identified as an important source of modern carbon in primary organic aerosol.

  58. Sardans J, Gargallo-Garriga A, Pérez-Trujillo M, Parella TJ, Seco R, Filella I, Peñuelas J (2014) Metabolic responses of Quercus ilex seedlings to wounding analyzed with nuclear magnetic resonance profiling. Plant Biology, 16: 395-403 Supplement Abstract

    Plants defend themselves against herbivory at several levels. One of these is the synthesis of inducible chemical defences. Using NMR metabolomic techniques, we studied the metabolic changes of plant leaves after a wounding treatment simulating herbivore attack in the Mediterranean sclerophyllous tree Quercus ilex. First, an increase in glucose content was observed in wounded plants. There was also an increase in the content of C-rich secondary metabolites such as quinic acid and quercitol, both related to the shikimic acid pathway and linked to defence against biotic stress. There was also a shift in N-storing amino acids, from leucine and isoleucine to asparagine and choline. The observed higher content of asparagine is related to the higher content of choline through serine that was proved to be the precursor of choline. Choline is a general anti-herbivore and pathogen deterrent. The study shows the rapid metabolic response of Q. ilex in defending its leaves, based on a rapid increase in the production of quinic acid, quercitol and choline. The results also confirm the suitability of 1H NMR-based metabolomic profiling studies to detect global metabolome shifts after wounding stress in tree leaves, and therefore its suitability in ecometabolomic studies.

  59. 2013

  60. Filella I, Primante C, Llusia J, Martín González AM, Seco R, Farré-Armengol G, Rodrigo A, Bosch J, Peñuelas J (2013) Floral advertisement scent in a changing plant-pollinators market. Scientific Reports, 3: 3434 Supplement1 Supplement2 Abstract

    Plant-pollinator systems may be considered as biological markets in which pollinators choose between different flowers that advertise their nectar/pollen rewards. Although expected to play a major role in structuring plant-pollinator interactions, community-wide patterns of flower scent signals remain largely unexplored. Here we show for the first time that scent advertisement is higher in plant species that bloom early in the flowering period when pollinators are scarce relative to flowers than in species blooming later in the season when there is a surplus of pollinators relative to flowers. We also show that less abundant flowering species that may compete with dominant species for pollinator visitation early in the flowering period emit much higher proportions of the generalist attractant ß-ocimene. Overall, we provide a first community-wide description of the key role of seasonal dynamics of plant-specific flower scent emissions, and reveal the coexistence of contrasting plant signaling strategies in a plant-pollinator market.

  61. Peñuelas J, Guenther A, Rapparini F, Llusia J, I Filella I, Seco R, Estiarte M, Mejia-Chang M, Ogaya R, Ibañez J, Sardans J, Castaño LM, Turnipseed A, Duhl T, Harley P, Vila J, Estavillo JM, Villanueva S, Facini O, Baraldi R, Geron C, Mak J, Patton EG, Jiang X, Greenberg J (2013) Intensive measurements of gas, water, and energy exchange between vegetation and troposphere during the MONTES Campaign in a vegetation gradient from short semi-desertic shrublands to tall wet temperate forests in the NW Mediterranean basin. Atmospheric Environment, 75: 348-364 Abstract

    • We present a multidisciplinary biosphere-atmosphere field campaign.
    • We measured a gradient from semi-desertic shrublands to wet temperate forests.
    • A wide range of instruments and vertical platforms were used.
    • Land cover strongly influenced emissions of BVOCs and gas, energy and water exchange.
    • Vegetation has strong potential for feed-back to atmospheric chemistry and climate.
    MONTES (“Woodlands”) was a multidisciplinary international field campaign aimed at measuring energy, water and especially gas exchange between vegetation and atmosphere in a gradient from short semi-desertic shrublands to tall wet temperate forests in NE Spain in the North Western Mediterranean Basin (WMB). The measurements were performed at a semidesertic area (Monegros), at a coastal Mediterranean shrubland area (Garraf), at a typical Mediterranean holm oak forest area (Prades) and at a wet temperate beech forest (Montseny) during spring (April 2010) under optimal plant physiological conditions in driest-warmest sites and during summer (July 2010) with drought and heat stresses in the driest–warmest sites and optimal conditions in the wettest–coolest site. The objective of this campaign was to study the differences in gas, water and energy exchange occurring at different vegetation coverages and biomasses. Particular attention was devoted to quantitatively understand the exchange of biogenic volatile organic compounds (BVOCs) because of their biological and environmental effects in the WMB. A wide range of instruments (GC–MS, PTR-MS, meteorological sensors, O3 monitors,…) and vertical platforms such as masts, tethered balloons and aircraft were used to characterize the gas, water and energy exchange at increasing footprint areas by measuring vertical profiles. In this paper we provide an overview of the MONTES campaign: the objectives, the characterization of the biomass and gas, water and energy exchange in the 4 sites-areas using satellite data, the estimation of isoprene and monoterpene emissions using MEGAN model, the measurements performed and the first results. The isoprene and monoterpene emission rates estimated with MEGAN and emission factors measured at the foliar level for the dominant species ranged from about 0 to 0.2 mg m-2 h-1 in April. The warmer temperature in July resulted in higher model estimates from about 0 to ca. 1.6 mg m-2 h-1 for isoprene and ca. 4.5 mg m-2 h-1 for monoterpenes, depending on the site vegetation and footprint area considered. There were clear daily and seasonal patterns with higher emission rates and mixing ratios at midday and summer relative to early morning and early spring. There was a significant trend in CO2 fixation (from 1 to 10 mg C m-2 d-1), transpiration (from 1–5 kg C m-2 d-1), and sensible and latent heat from the warmest–driest to the coolest–wettest site. The results showed the strong land-cover-specific influence on emissions of BVOCs, gas, energy and water exchange, and therefore demonstrate the potential for feed-back to atmospheric chemistry and climate.

  62. Seco R, Peñuelas J, Filella I, Llusia J, Schallhart S, Metzger A, Müller M, and Hansel A (2013) Volatile Organic Compounds in the Western Mediterranean Basin: urban and rural winter measurements during the DAURE campaign. Atmospheric Chemistry and Physics, 13: 4291-4306 Supplement Abstract

    Atmospheric volatile organic compounds (VOCs) have key environmental and biological roles, but little is known about the daily VOC mixing ratios in Mediterranean urban and natural environments. We measured VOC mixing ratios concurrently at an urban and a rural site during the winter DAURE campaign in the northeastern Iberian Peninsula, by means of PTR-MS at both locations: a PTR-Quad-MS at the urban site and a PTR-ToF-MS at the rural site. All VOC mixing ratios measured were higher at the urban site (e.g. acetaldehyde, isoprene, benzene, and toluene with averages up to 1.68, 0.31, 0.58 and 2.71 ppbv, respectively), with the exception of some short chain oxygenated VOCs such as acetone (with similar averages of 0.7-1.6 ppbv at both sites). Their average diurnal pattern also differed between the sites. Most of the VOCs at the urban location showed their highest mixing ratios in the morning and evening. These peaks coincided with traffic during rush hours, the main origin of most of the VOCs analyzed. Between these two peaks, the sea breeze transported the urban air inland, thus helping to lower the VOC loading at the urban site. At the rural site, most of the measured VOCs were advected by the midday sea breeze, yielding the highest daily VOC mixing ratios (e.g. acetaldehyde, isoprene, benzene, and toluene with averages up to 0.65, 0.07, 0.19, and 0.41 ppbv, respectively). Only biogenic monoterpenes showed a clear local origin at this site. In addition, the concentrations of fine particulate matter observed at both sites, together with the synoptic meteorological conditions and radio-sounding data, allowed the identification of different atmospheric scenarios that had a clear influence on the measured VOC mixing ratios. These results highlight the differences and relationships in VOC mixing ratios between nearby urban and rural areas in Mediterranean regions. Further research in other urban-rural areas is warranted to better understand the urban-rural influence on atmospheric VOC mixing ratios under different atmospheric conditions.

  63. 2012

  64. Llusia J, Peñuelas J, Seco R, Filella I (2012) Seasonal changes in the daily emission rates of terpenes by Quercus ilex and the atmospheric concentrations of terpenes in the natural park of Montseny, NE Spain. Journal of Atmospheric Chemistry, 69 (3): 215-230 Abstract

    We studied the daily patterns in the rates of terpene emissions by the montane holm oak, Quercus ilex, in three typical days of winter and three typical days of summer in Montseny, a natural park near Barcelona, and related them to the air concentrations of terpenes, ozone and NO2. Terpene emission rates were about 10 times higher in summer than in winter. Emissions virtually stopped in the dark. In both seasons, rates of terpene emissions were well correlated with light, air temperature and relative humidity. Rates of emissions were also correlated with stomatal conductance and the rates of transpiration and photosynthesis. Almost all the individual terpenes identified followed the same pattern as total terpenes. The most abundant terpene was α-pinene, followed by sabinene + β-pinene, limonene, myrcene, camphene and α-phellandrene. Atmospheric terpene concentrations were also about 10 times higher in summer than in winter. A significant diurnal pattern with maxima at midday was observed, especially in summer. The increase by one order of magnitude in the concentrations of these volatile isoprenoids highlights the importance of local biogenic summer emissions in these Mediterranean forested areas which also receive polluted air masses from nearby or distant anthropic sources. Atmospheric concentrations of O3 and NO2 were also significantly higher in summer and at midday hours. In both seasons, concentrations of O3 were significantly correlated with concentrations of terpenes and NO2 in the air and with rates of terpene emission.

  65. Reche C, Viana M, Amato F, Alastuey A, Moreno T, Hillamo R, Teinilä K, Saarnio K, Seco R, Peñuelas J, Mohr C, Prévôt ASH, Querol X (2012) Biomass burning contributions to urban aerosols in a coastal Mediterranean City. Science of The Total Environment, 427-428: 175-190 Supplement Abstract

    • We identify the biomass burning impact to PM levels in a Mediterranean urban site.
    • It was possible by specific tracers: levoglucosan, K+ and OC.
    • The PMF (ME-2) model allowed the quantification of biomass burning contribution to PM levels.
    • Biomass burning emissions accounted for 3% of the annual PM10 and PM2.5 and 5% of PM1.
    • Biomass burning emission contribution to OC levels was constant among PM fractions.
    Mean annual biomass burning contributions to the bulk particulate matter (PMX) load were quantified in a southern-European urban environment (Barcelona, Spain) with special attention to typical Mediterranean winter and summer conditions. In spite of the complexity of the local air pollution cocktail and the expected low contribution of biomass burning emissions to PM levels in Southern Europe, the impact of these emissions was detected at an urban background site by means of tracers such as levoglucosan, K+ and organic carbon (OC). The significant correlation between levoglucosan and OC (r2 = 0.77) and K+ (r2 = 0.65), as well as a marked day/night variability of the levoglucosan levels and levoglucosan/OC ratios was indicative of the contribution from regional scale biomass burning emissions during night-time transported by land breezes. In addition, on specific days (21–22 March), the contribution from long-range transported biomass burning aerosols was detected.

    Quantification of the contribution of biomass burning aerosols to PM levels on an annual basis was possible by means of the Multilinear Engine (ME). Biomass burning emissions accounted for 3% of PM10 and PM2.5 (annual mean), while this percentage increased up to 5% of PM1. During the winter period, regional-scale biomass burning emissions (agricultural waste burning) were estimated to contribute with 7 ± 4% of PM2.5 aerosols during night-time (period when emissions were clearly detected). Long-range transported biomass burning aerosols (possibly from forest fires and/or agricultural waste burning) accounted for 5 ± 2% of PM2.5 during specific episodes. Annually, biomass burning emissions accounted for 19%–21% of OC levels in PM10, PM2.5 and PM1. The contribution of this source to K+ ranged between 48% for PM10 and 97% for PM1 (annual mean). Results for K+ from biomass burning evidenced that this tracer is mostly emitted in the fine fraction, and thus coarse K+ could not be taken as an appropriate tracer of biomass burning.

  66. Mohr C, Decarlo PF, Heringa MF, Chirico R, Slowik JG, Richter R, Reche C, Alastuey A, Querol X, Seco R, Peñuelas J, Jiménez JL, Crippa M, Zimmermann R, Baltensperger U, Prévôt ASH (2012) Identification and quantification of organic aerosol from cooking and other sources in Barcelona using aerosol mass spectrometer data. Atmospheric Chemistry and Physics, 12: 1649-1665 Supplement Abstract

    PM1 (particulate matter with an aerodynamic diameter <1 µm) non-refractory components and black carbon were measured continuously together with additional air quality and atmospheric parameters at an urban background site in Barcelona, Spain, during March 2009 (campaign DAURE, Determination of the sources of atmospheric Aerosols in Urban and Rural Environments in the western Mediterranean). Positive matrix factorization (PMF) was conducted on the organic aerosol (OA) data matrix measured by an aerosol mass spectrometer, on both unit mass (UMR) and high resolution (HR) data. Five factors or sources could be identified: LV-OOA (low-volatility oxygenated OA), related to regional, aged secondary OA; SV-OOA (semi-volatile oxygenated OA), a fresher oxygenated OA; HOA (hydrocarbon-like OA, related to traffic emissions); BBOA (biomass burning OA) from domestic heating or agricultural biomass burning activities; and COA (cooking OA). LV-OOA contributed 28% to OA, SV-OOA 27%, COA 17%, HOA 16%, and BBOA 11%. The COA HR spectrum contained substantial signal from oxygenated ions (O:C: 0.21) whereas the HR HOA spectrum had almost exclusively contributions from chemically reduced ions (O:C: 0.03). If we assume that the carbon in HOA is fossil while that in COA and BBOA is modern, primary OA in Barcelona contains a surprisingly high fraction (59%) of non-fossil carbon.

    This paper presents a method for estimating cooking organic aerosol in ambient datasets based on the fractions of organic mass fragments at m/z 55 and 57: their data points fall into a V-shape in a scatter plot, with strongly influenced HOA data aligned to the right arm and strongly influenced COA data points aligned to the left arm. HR data show that this differentiation is mainly driven by the oxygen-containing ions C3H3O+ and C3H5O+, even though their contributions to m/z 55 and 57 are low compared to the reduced ions C4H7+ and C4H9+. A simple estimation method based on the markers m/z 55, 57, and 44 is developed here and allows for a first-order-estimation of COA in urban air. This study emphasizes the importance of cooking activities for ambient air quality and confirms the importance of chemical composition measurements with a high mass and time resolution.

      Listed Highly Cited Article as of January/February 2017 (top 1% of the field of Geosciences; WebofScience Essential Science Indicators, Clarivate Analytics)
  67. 2011

  68. Seco R, Peñuelas J, Filella I, Llusià J, Molowny-Horas R, Schallhart S, Metzger A, Müller M, and Hansel A (2011) Contrasting winter and summer VOC mixing ratios at a forest site in the Western Mediterranean Basin: the effect of local biogenic emissions. Atmospheric Chemistry and Physics, 11: 13161-13179 Supplement Abstract

    Atmospheric volatile organic compounds (VOCs) are involved in ozone and aerosol generation, thus having implications for air quality and climate. VOCs and their emissions by vegetation also have important ecological roles as they can protect plants from stresses and act as communication cues between plants and between plants and animals. In spite of these key environmental and biological roles, the reports on seasonal and daily VOC mixing ratios in the literature for Mediterranean natural environments are scarce.

    We conducted seasonal (winter and summer) measurements of VOC mixing ratios in an elevated (720 m a.s.l.) holm oak Mediterranean forest site near the metropolitan area of Barcelona (NE Iberian Peninsula). Methanol was the most abundant compound among all the VOCs measured in both seasons. While aromatic VOCs showed almost no seasonal variability, short-chain oxygenated VOCs presented higher mixing ratios in summer, presumably due to greater emission by vegetation and increased photochemistry, both enhanced by the high temperatures and solar radiation in summer. Isoprenoid VOCs showed the biggest seasonal change in mixing ratios: they increased by one order of magnitude in summer, as a result of the vegetation's greater physiological activity and emission rates. The maximum diurnal concentrations of ozone increased in summer too, most likely due to more intense photochemical activity and the higher levels of VOCs in the air.

    The daily variation of VOC mixing ratios was mainly governed by the wind regime of the mountain, as the majority of the VOC species analyzed followed a very similar diel cycle. Mountain and sea breezes that develop after sunrise advect polluted air masses to the mountain. These polluted air masses had previously passed over the urban and industrial areas surrounding the Barcelona metropolitan area, where they were enriched in NOx and in VOCs of biotic and abiotic origin. Moreover, these polluted air masses receive additional biogenic VOCs emitted in the local valley by the vegetation, thus enhancing O3 formation in this forested site. The only VOC species that showed a somewhat different daily pattern were monoterpenes because of their local biogenic emission. Isoprene also followed in part the daily pattern of monoterpenes, but only in summer when its biotic sources were stronger. The increase by one order of magnitude in the concentrations of these volatile isoprenoids highlights the importance of local biogenic summer emissions in these Mediterranean forested areas which also receive polluted air masses from nearby or distant anthropic sources.

  69. Minguillón MC, Perron N, Querol X, Szidat S, Fahrni SM, Alastuey A, Jimenez JL, Mohr C, Ortega AM, Day DA, Lanz VA, Wacker L, Reche C, Cusack M, Amato F, Kiss G, Hoffer A, Decesari S, Moretti F, Hillamo R, Teinilä K, Seco R, Peñuelas J, Metzger A, Schallhart S, Müller M, Hansel A, Burkhart JF, Baltensperger U, Prévôt ASH (2011) Fossil versus contemporary sources of fine elemental and organic carbonaceous particulate matter during the DAURE campaign in Northeast Spain. Atmospheric Chemistry and Physics, 11: 12067-12084 Supplement Abstract

    We present results from the international field campaign DAURE (Determination of the sources of atmospheric Aerosols in Urban and Rural Environments in the Western Mediterranean), with the objective of apportioning the sources of fine carbonaceous aerosols. Submicron fine particulate matter (PM1) samples were collected during February–March 2009 and July 2009 at an urban background site in Barcelona (BCN) and at a forested regional background site in Montseny (MSY). We present radiocarbon (14C) analysis for elemental and organic carbon (EC and OC) and source apportionment for these data. We combine the results with those from component analysis of aerosol mass spectrometer (AMS) measurements, and compare to levoglucosan-based estimates of biomass burning OC, source apportionment of filter data with inorganic composition + EC + OC, submicron bulk potassium (K) concentrations, and gaseous acetonitrile concentrations.

    At BCN, 87 % and 91 % of the EC on average, in winter and summer, respectively, had a fossil origin, whereas at MSY these fractions were 66 % and 79 %. The contribution of fossil sources to organic carbon (OC) at BCN was 40 % and 48 %, in winter and summer, respectively, and 31 % and 25 % at MSY. The combination of results obtained using the 14C technique, AMS data, and the correlations between fossil OC and fossil EC imply that the fossil OC at Barcelona is ∼47 % primary whereas at MSY the fossil OC is mainly secondary (∼85 %). Day-to-day variation in total carbonaceous aerosol loading and the relative contributions of different sources predominantly depended on the meteorological transport conditions. The estimated biogenic secondary OC at MSY only increased by ∼40 % compared to the order-of-magnitude increase observed for biogenic volatile organic compounds (VOCs) between winter and summer, which highlights the uncertainties in the estimation of that component. Biomass burning contributions estimated using the 14C technique ranged from similar to slightly higher than when estimated using other techniques, and the different estimations were highly or moderately correlated. Differences can be explained by the contribution of secondary organic matter (not included in the primary biomass burning source estimates), and/or by an overestimation of the biomass burning OC contribution by the 14C technique if the estimated biomass burning EC/OC ratio used for the calculations is too high for this region. Acetonitrile concentrations correlate well with the biomass burning EC determined by 14C. K is a noisy tracer for biomass burning.

  70. Seco R, Filella I, Llusià J, Peñuelas J (2011) Methanol as a signal triggering isoprenoid emissions and photosynthetic performance in Quercus ilex. Acta Physiologiae Plantarum, 33 (6): 2413-2422 Abstract

    Several volatile organic compounds (VOCs) have been reported as having a communication role between plants and also between plants and animals. We aimed to test whether methanol, a short-chain oxygenated VOC, could also have a signalling role between plants. We monitored photosynthetic performance and VOC exchange rates of Quercus ilex L. saplings before and after two different treatments: (a) clipping of some leaves to simulate an attack by herbivores and (b) fumigation with gaseous methanol for 5 h to simulate the amount of methanol a plant could receive from surrounding plants if those had been already attacked by herbivores. The clipping treatment enhanced the photosynthetic rates, the chlorophyll a to b ratio and the carotenoid to chlorophyll ratio of non-clipped leaves, suggesting an activation of plant protective metabolism. Also, a small but interesting systemic (in non-clipped leaves) increase in methanol emission rates was observed, which agrees with the possibility that methanol may act as a signalling cue. The methanol fumigation treatment induced an increase in the actual photochemical efficiency of PSII and also in the carotenoid to chlorophyll ratio. Methanol fumigation also promoted a 14% increase in the monoterpene emission rate, 1 day after the treatment, a similar response to the ones induced by other signalling VOCs. The enhanced monoterpene emissions could add to the blend of VOCs emitted after stress and be part of further signalling pathways, thus forwarding the message started by methanol. This study suggests that clipping and methanol fumigation at natural concentrations elicit significant neighbour plant physiological responses and further BVOC emissions.

  71. Filella I, Bosch J, Llusià J, Seco R, Peñuelas J (2011) The role of frass and cocoon volatiles in host location by Monodontomerus aeneus, a parasitoid of Megachilid solitary bees. Environmental Entomology, 40 (1): 126-131 Abstract

    Monodontomerus aeneus (Fonscolombe) is a parasitic wasp that oviposits on the prepupae and pupae of Osmia cornuta (Latreille) and other solitary bee species. A two-armed olfactometer was used to test the olfactory attractiveness of O. cornuta prepupae, cocoon, and larval frass to female M. aeneus. Both cocoon and frass attracted the female parasitoids, but frass alone was more attractive than the cocoon and the cocoon with frass was more attractive than frass alone. Female parasitoids were not attracted by the host prepupa. M33 (methanol) was the organic volatile most emitted by cocoons and m61 (acetic acid) was the compound most emitted by frass. However, cocoons showed higher emission for almost all compounds, including m61 (acetic acid). Although acetic acid alone attracted M. aeneus, a complex volatile signal is probably involved in the attraction process because the ratio of acetic acid and acetaldehyde characteristic of the frass was more attractive than other ratios.

  72. 2009

  73. Peñuelas J, Filella I, Seco R, Llusià J (2009) Increase in isoprene and monoterpene emissions after re-watering of droughted Quercus ilex seedlings. Biologia Plantarum, 53 (2): 351-354 Abstract

    We followed the diurnal cycles of isoprenoid emissions from Quercus ilex seedlings under drought and after re-watering. We found that Quercus ilex, generally considered a non-isoprene emitter, also emitted isoprene although at low rates. The emission rates of isoprene reached 0.37 ± 0.02 nmol m-2 s-1 in controls, 0.15 ± 0.03 nmol m-2 s-1 under drought and 0.35 ± 0.04 nmol m-2 s-1 after re-watering, while emission rates of monoterpenes reached 11.0 ± 3.0, 7.0 ± 1.0 and 23.0 ± 5.0 nmol m-2 s-1, respectively. Emission rates recovered faster after re-watering than photosynthetic rate and followed diurnal changes in irradiance in controls and under drought, but in leaf temperature after re-watering.

  74. Filella I, Peñuelas J, Seco R (2009) Short-chained oxygenated VOC emissions in Pinus halepensis in response to changes in water availability. Acta Physiologiae Plantarum, 31: 311-318 Abstract

    Short-chained oxygenated VOC (oxVOCs) emissions from Pinus halepensis saplings were monitored in response to changes in water availability. Online measurements were made with a proton transfer reaction—mass spectrometer under controlled conditions, together with CO2 and H2O exchange measurements. Masses corresponding to methanol and acetone were the most emitted oxVOCs. All the oxVOC exchanges, except that of acetone (M59), were significantly related to stomatal conductance and transpiration. Acetaldehyde (M45) emission showed, moreover, a strong dependence on the concentration of acetaldehyde in the ambient: stomatal opening (stomatal conductance above 75 mmol m-2 s-1) only allowed increased emissions when external concentration were below 6 ppb. Acetone (M59) presented an important peak of emission following light and stomatal opening in the morning when plants were water stressed. Thus, the alterations in oxVOC emissions in P. halepensis caused by the water deficit seem to be mainly driven by water stress effect on stomatal closure and oxVOC air concentrations.

  75. 2008

  76. Seco R, Peñuelas J, Filella I (2008) Formaldehyde emission and uptake by Mediterranean trees Quercus ilex and Pinus halepensis. Atmospheric Environment, 42: 7907-7914 Abstract

    Formaldehyde (FA) is an ubiquitous gas in the atmosphere which reaches notable concentrations in polluted areas and can have great impact on human health. We studied FA exchange between air and two widespread Mediterranean tree species, Quercus ilex and Pinus halepensis. Experiments were conducted at the leaf level under laboratory conditions using air from outside the building. In both plant species FA exchange was mainly determined by the atmospheric mixing ratios, with a compensation point calculated around 20 ppbv. Higher values led to uptake and lower values to emission. The second factor that regulated FA exchange was stomatal conductance. FA exchange followed a diurnal cycle with the greatest exchange when stomatal conductance was at maximum. Such stomatal control is consistent with previous studies and is probably due to the high water solubility of FA, resulting in stomatal transpiration being its main exchange pathway. We also observed this relationship between stomatal conductance and FA exchange under conditions of drought and posterior rewatering, in which changes in stomatal conductance were paralleled by changes in FA exchange. Under projected future conditions of enhanced aridity in the Mediterranean, drought-driven limitations of FA exchange may be more relevant.

  77. 2007

  78. Seco R, Peñuelas J, Filella I (2007) Short-chain oxygenated VOCs: Emission and uptake by plants and atmospheric sources, sinks, and concentrations. Atmospheric Environment, 41: 2477–2499 Abstract

    Emissions of volatile organic compounds (VOCs) have multiple atmospheric implications and play many roles in plant physiology and ecology. Among these VOCs, growing interest is being devoted to a group of short-chain oxygenated VOCs (oxVOCs). Technology improvements such as proton transfer reaction-mass spectrometry are facilitating the study of these hydrocarbons and new data regarding these compounds is continuously appearing. Here we review current knowledge of the emissions of these oxVOCs by plants and the factors that control them, and also provide an overview of sources, sinks, and concentrations found in the atmosphere.

    The oxVOCs reviewed here are formic and acetic acids, acetone, formaldehyde, acetaldehyde, methanol, and ethanol. In general, because of their water solubility (low gas–liquid partitioning coefficient), the plant-atmosphere exchange is stomatal-dependent, although it can also take place via the cuticle. This exchange is also determined by atmospheric mixing ratios. These compounds have relatively long atmospheric half-lives and reach considerable concentrations in the atmosphere in the range of ppbv. Likewise, under non-stressed conditions plants can emit all of these oxVOCs together at fluxes ranging from 0.2 up to 4.8 µg(C)g-1(leaf dry weight) h-1 and at rates that increase several-fold when under stress.

    Gaps in our knowledge regarding the processes involved in the synthesis, emission, uptake, and atmospheric reactivity of oxVOCs precludes the clarification of exactly what is conditioning plant-atmosphere exchange—and also when, how, and why this occurs—and these lacunae therefore warrant further research in this field.

      Listed 20th most downloaded paper of the journal Atmospheric Environment for the period April-June 2007

      Named Top-50 Highly Cited Author 2007-2010 for the journal Atmospheric Environment


  1. Vettikkat L, Miettinen P, Buchholz A, Rantala P, Yu H, Schallhart S, Seco R, Männistö E, Tuittila E-S, Guenther AB, Schobesberger S (2022) Dataset: High emission rates and strong temperature response make boreal wetlands a large source of isoprene and terpenes. Dataset on Zenodo
  2. Seco R, Holst T, Davie-Martin CL, Simin T, Guenther A, Pirk N, Rinne J, Rinnan R (2022) Dataset: Strong isoprene emission response to temperature in tundra vegetation. Dataset on Zenodo
  3. Seco R, Holst T, Matzen MS, Westergaard-Nielsen A, Li T, Simin T, Jansen J, Crill P, Friborg T, Rinne J, Rinnan R (2020) Dataset: Volatile organic compound fluxes in a subarctic peatland and lake. Dataset on Zenodo
  4. Powers JM, Seco R, Faiola CL, Sakai AK, Weller SG, Campbell DR, Guenther A (2020) Floral scent dynamics of Schiedea kaalae and Schiedea hookeri. Dataset on Dryad
  5. (2016) KORUS-AQ campaign: Cl2 and ClNO2 mixing ratios in air, measured onboard the NASA DC-8 aircraft over South Korea. Dataset on the NASA website
  6. (2016) KORUS-AQ campaign: OH reactivity; Cl2, ClNO2, NOx and VOC (PTR-TOF-MS) mixing ratios in air, all measured at the Taehwa forest site in South Korea. Dataset on the NASA website
  7. (2014) GOAMAZON 2014/15 campaign: Hydroxyl radical (OH) and sulfuric acid (H2SO4) concentrations (CIMS) at the T3 site in Manacapuru (Amazonas, Brasil). Dataset on the ARM website
  8. (2014) GOAMAZON 2014/15 campaign: SRI-PTR-TOF-MS VOC data from the T3 site in Manacapuru (Amazonas, Brasil). Info on the ARM website Dataset on the ARM website
  9. (2013) DISCOVER-AQ campaign: VOC mixing ratios (PTR-TOF-MS) in air, measured at the Fresno ground site in California (USA). Dataset on the NASA website

Book chapters

  1. Peñuelas J, Filella I, Estiarte M, Ogaya R, Llusià J, Sardans J, Jump A, Curiel J, Carnicer J, Ruthishauser T, Rico L, Keenan T, Garbulsky M, Coll M, Diaz de Quijano M, Seco R, Rivas A, Boada M, Stefanescu C, Lloret F, Terradas J (2010) Impactes, vulnerabilitat i retroalimentacions climàtiques als ecosistemes terrestres catalans. In: Llebot E (ed.). El Canvi Climàtic a Catalunya. 2n Informe del Grup d’Experts en Canvi Climàtic de Catalunya, pp. 373–407 . Published by Departament de Medi Ambient i Habitatge (Generalitat de Catalunya), Servei Meteorològic de Catalunya and Institut d'Estudis Catalans
  2. Peñuelas J, Filella I, Estiarte M, Ogaya R, Llusià J, Sardans J, Jump A, Garbulsky M, Coll M, Diaz de Quijano M, Seco R, Blanch JS, Owen S, Curiel J, Carnicer J, Boada M, Stefanescu C, Lloret F, Terradas J (2009) Constatacions biològiques del canvi climàtic a Catalunya. In: Aigua i canvi climàtic. Diagnosi dels impactes previstos a Catalunya, pp. 43–52 . Published by Departament de Medi Ambient i Habitatge and Agència Catalana de l’Aigua, Generalitat de Catalunya


  1. Seco R, Peñuelas J, Filella I, Llusià J, Molowny-Horas R (2012) Els COVs al Montseny: entre l'smog urbà i la biogeneració. UAB Divulga, mar 2012
  2. Seco R, Filella I, Llusià J, Peñuelas J (2012) Les plantes s'avisen del perill immediat. UAB Divulga, feb. 2012

Other publications

  1. Li L-Y, Guenther AB, Gu D, Seco R, Nagalingam S (2020). Impact of short-term drought stress on volatile organic compounds emissions from Pinus massoniana. China Environmental Science, 40: 3776-3780 Abstract

    To explore the impact of drought on BVOC emissions, dynamic enclosure system and TD-GC-TOFMS were used to conduct laboratory measurements of BVOC emission from Pinus massoniana under short-term drought stress. The changes in emission rates and composition were analyzed quantitatively. The results showed that emission of isoprene was inhibited under drought stress, with a drop of around 50% in emission rate. Monoterpene and sesquiterpene emission rates were enhanced to 137.85 µg/(m2·h) and 0.98 µg/(m2·h) which were 2.9 and 2.0 times as high as those without stress, respectively. Except trans-a-bergamotene, emissions of all the detected monoterpene and sesquiterpene compounds were promoted under drought stress. Those emission rates were 1.3~42.4 times as high as those without stress. Among them, 3-carene emission had the most sensitive response to drought stress, while a-fenchene, a-phellandrene, and trans-caryophyllene had the lowest sensitivity. Under drought stress, the emission compositions of monoterpene and sesquiterpene were changed, but the dominant compounds remained the same. The main components of monoterpene were a-pinene, sabinene, and ß-pinene, accounting for 48%, 17%, and 17% in the total monoterpene emissions, respectively. Trans-caryophyllene and longifolene dominated sesquiterpene emissions with contributions of 57% and 34%, respectively.

  2. Li L-Y, Guenther AB, Gu D, Seco R, Nagalingam S (2019). Biogenic emission profile of volatile organic compounds from poplar, sweetgum, and pine trees. China Environmental Science, 39: 4966-4973 Abstract

    In order to study the characteristics of biogenic volatile organic compounds (BVOCs) emission from typical trees and obtain their basic emission rates for each BVOC compound, a dynamic enclosed system was used to conduct laboratory measurements on poplar, sweetgum, and pine trees. BVOC compounds including isoprene, monoterpenes, sesquiterpenes, alkanes, and alkenes were analyzed by TD-GC-TOFMS. The normalized species-specific BVOC emission rates of three tree species were calculated and their emission profiles were investigated. The total BVOC emission rates of Populus trichocarpa, Liquidambar styraciflua, and Pinus massoniana were 19.51, 7.19, and 0.67μg/(g·h) (2086.91, 562.35, and 104.03μg/(m2·h)), respectively. Populus trichocarpa had the highest isoprene emission rate of 18.51μg/(g·h), contributing 94.86% to the total BVOC emissions. Pinus massoniana had a lower isoprene contribution (4.03%), but the highest monoterpenes contribution (49.09%. Liquidambar styraciflua had the highest monoterpenes emission rate of 0.84μg/(g·h). Sesquiterpenes contributed less than 1.5% to the total BVOC emissions for the three plants. The emission rates of alkanes for each tree species were generally higher than those of sesquiterpenes, and some were even higher than those of isoprene and monoterpenes. Trans-β-ocimene was the predominated monoterpene for Populus trichocarpa, accounting for 99.84% of its total monoterpene emissions. The monoterpenes emitted by Liquidambar styraciflua.was mainly composed by Sabinene and β-pinene. α-Pinene, sabinene, and β-pinene were observed as the dominated monoterpenes for Pinus massoniana. Trans-caryophyllene, humulene, δ-cadinene, and β-guaiene were prominent sesquiterpenes. Alkanes emitted from the three plants were mainly C4 and C5 compounds, of which particularly were isobutane and butane. 1-Butene was the most abundant alkene for all plants.

  3. Batalha S, Park JH, Alves E, Santana R, Seco R, Vega Bustillos JO, Smith J, Guenther A, Tóta J (2018). Aspectos micrometeorológicos da emissão de monoterpenos em uma floresta na Amazônia central. Ciência e Natura, 40: 150-154 Abstract

    Este trabalho teve por objetivo apresentar resultados sobre a razão de mistura e fluxo de monoterpenos em uma região de floresta da Amazônia brasileira. Utilizou-se instrumentação da micrometeorologia (com o uso de um Anemômetro Sônico) e da química analítica através de um espectrômetro de massa com próton transferência (Proton Transfer Reaction – Time of Flight – Mass Spectrometer, PTR-ToF-MS). A calibração do espectrômetro foi realizada regularmente com a utilização de uma mistura gravimétrica de gás padrão contendo diferentes massas de compostos orgânicos voláteis. Os resultados evidenciaram razão de mistura média de monoterpenos de 0,185 ppbv e fluxo de emissão máxima de 1,495 mg m-2 h-1. Concluiu-se que esta região apresentou significativa emissão de monoterpenos em relação a outra floresta tropical na Amazônia central, evidenciando a necessidade de ampliar estudos sobre a química atmosférica em diferentes florestas da bacia amazônica.

  4. Seco R, Karl T, Turnipseed A, Greenberg J, Guenther A, Llusia J, Peñuelas J, Dicken U, Rotenberg E, Rohatyn S, Preisler Y, Yakir D (2014). Comparable Monoterpene emission from pine forests across 500 mm precipitation gradient in the semi-arid transition zone. Geophysical Research Abstracts 16, EGU2014-9148
  5. Pandolfi M, Cusack M, Pey J, Alastuey A, Querol X, Reche C, Moreno T, Viana M, Cubison M, Ortega A, Nemitz E, di Marco C, Artiñano B, Gómez Moreno F, Revuelta MA, Peñuelas J, Seco R, Jimenez JL (2010). Intensive Aerosol Measurements during the DAURE Campaign at an EUSAAR Rural Site in the NW Mediterranean. International Aerosol Conference 2010 Abstract Book, Helsinki, Finland
  6. Kleist E, dal Maso M, Kiendler-Scharr A, Hoffmann Th, Hohaus Th, Llusià J, Mentel Th, Peñuelas J, Reinnig Ch, Seco R, Tillman R, Uerlings, R, Warnke J, Wildt J (2008). SOA formation from stress induced BVOC emissions. Geophysical Research Abstracts 10, A-03145
Clicks on PDF links are assumed to be peer petitions of reprints to the authors. PDF files provided here are only for personal scientific use. The copyright remains with the respective copyright owners. Always refer to the publisher links for the version of record.