UC Irvine UC Irvine Previously Published Works Title Natural volatile organic compound emissions from plants and their roles in oxidant balance and particle formation Permalink https://escholarship.org/uc/item/65s8h857 Journal Geophysical Monograph Series, 186 ISSN 0065-8448 Authors Kesselmeier, J Guenther, A Hoffmann, T et al. Publication Date 2009 DOI 10.1029/2008GM000717 License https://creativecommons.org/licenses/by/4.0/ 4.0 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Natural Volatile Organic Compound Emissions From Plants and Their Roles in Oxidant Balance and Particle Formation Jürgen Kesselmeier,1 Alex Guenther,2 Thorsten Hoffmann,3 Maria Teresa Piedade,4 and Jörg Warnke3 Numerous biogenic volatile organic compounds (VOC) species are released into the atmosphere from tropical forests. Measuring all those which are relevant for atmospheric chemistry or for the carbon budget is challenging. Large-Scale Biosphere-Atmosphere (LBA) Experiment field campaigns substantially increased the number of field studies of isoprene and monoterpene emissions, as well as of the exchange of several other VOC species. This chapter reports about the progress made within LBA from primary emission measurements at the plant species level up to discussions of the oxidative capacity of the atmosphere and formation of secondary organic aerosol particles and cloud condensation nuclei from biogenic hydrocarbons. VOC emission from Amazonian ecotypes has strong effects on atmospheric chemistry, which are obviously not fully understood in the case of the tropical atmosphere. Atmospheric flux studies within numerous field experiments resulted in new knowledge about local to regional scale biogenic VOC exchange and improved modeling. New data obtained from field as well as from laboratory studies helped to characterize VOC emissions from the Amazonian forest underlying seasonality within dry and wet seasons. Furthermore, first insight was obtained into the potential of floodplain areas affected by long-lasting flooding periods which can cause special emission adaptation. 1Max Planck Institute for Chemistry, Mainz, Germany. 1. PROCESSES CONTROLLING TRACE 2National Center for Atmospheric Research, Boulder, Colorado, GAS EXCHANGE BETWEEN VEGETATION USA. AND THE ATMOSPHERE 3Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg University of Mainz, Mainz, Germany. 1.1. Ecological Biodiversity in Amazonia and Volatile 4 Instituto Nacional de Pesquisas da Amazônia, Manaus, Brasil. Organic Compounds Exchange Among the many challenges in studying the exchange of trace gases between forests and the atmosphere, how to ex- trapolate emission rates and fluxes is of highest importance. The emission of reactive volatile organic compounds (VOC) is highly plant species dependent [Kesselmeier and Staudt, Amazonia and Global Change 1999]. Furthermore, because we need to go to the level of Geophysical Monograph Series 186 a branch or leaf in a given plant species to identify the re- Copyright 2009 by the American Geophysical Union. lease of trace gases, results from measurements made above 10.1029/2008GM000717 the forest will be biased by chemical reactions occurring 183 184 NATURAL VOLATILE ORGANIC COMPOUND EMISSIONS FROM PLANTS during the time of transport. A reasonable approach for mod- atmospheric chemistry or the carbon budget is challenging. eling VOC release for European forests is to take into account Measurement techniques used are always limited to special the main forest tree species and their emission rate estimates groups of compounds and can only give a view into parts which have been identified at a branch or leaf level. However, of the story. Proton transfer reaction mass spectrometry this approach is impossible to apply to a tropical rainforest (PTR-MS) [Lindinger et al., 1998], which is now broadly with its huge biodiversity of species and phytogeographic used [see Karl and Guenther, 2004] can simultaneously de- regions, for which knowledge on the biotic and abiotic com- tect a large number of VOC species. Crutzen et al. [2000] ponents and relations is still scarce [Junk et al., 2000]. Bra- report on a large number of organic species measured using zilian Amazonia comprises an area of 5 million km2, 80% of this instrument over the rain forest in Suriname during an which is classified as so-called terra firmePires [ and Prance, aircraft campaign and also discuss a weakness of the PTR- 1985; Pires, 1973]. The remaining 20% can be divided into MS measurements, which is detecting ion masses without six phytogeographic formations according to their floristic clear identification. Nevertheless, the PTR-MS has become and structural characteristics, namely, the mixed and transi- a valuable tool to look for emissions of trace gases into the tional forests, the savannas, secondary forests, agricultural atmosphere. areas, and floodplains Braga[ , 1979; Junk, 1993]. Measurements made with more conservative tools have In floodplains, the seasonality imposed by the regular flood- nevertheless provided interesting data sets for non-methane ing of the big rivers is the most conspicuous feature inducing VOC species in the atmosphere over Amazonia. During the environmental constraints on the biota [Junk et al., 1989; Ay- Cooperative Large-Scale Biosphere-Atmosphere (LBA) res, 1986, 1993; Junk, 1997]. Water level fluctuation exhibits Airborne Regional Experiment 1998 (LBA-CLAIRE-98) amplitudes of 7 to 13 m between the high and low water con- campaign, Kesselmeier et al. [2000] measured the atmo- ditions with flooding periods of 1 to 8 months per year Junk[ , spheric mixing ratios of different species of VOC at a ground 1989; Kubitzki, 1989]. Different plant communities become es- station in an open forest site at Balbina, 100 km north of tablished depending on the length of inundation. Thus, changes Manaus. The most prominent VOC species present in air in the big river’s water levels and duration of inundation will during this wet season campaign (March–April) were for- drive species composition, diversity, and physiognomy of the maldehyde and isoprene, each up to several ppb. Concentra- floodplain forests Junk[ , 1989; Worbes, 1997; Ayres, 1993; tions of methyl vinyl ketone as well as methacrolein, both Wittmann et al., 2006; Piedade et al., 2001]. Plants exhibit oxidation products of isoprene, were significantly below 1 different capacities for tolerating periods of hypoxia or anoxia ppb, indicating a very low oxidation capacity in the lower as a consequence of the inundation, which can last from hours, atmospheric boundary layer, which is in agreement with a to days, weeks, or months [Parolin et al., 2004]. One of these daily ozone maximum of <20 ppb. Total monoterpene con- adaptations might be energy production by fermentation and centration was below 1 ppb. detoxification of compounds such as ethanol by transport into These data can be compared with a more comprehensive the canopy leaves with a subsequent re-metabolization and/or investigation during the LBA-EUSTACH campaigns (LBA- release into the atmosphere (see section 1.4) [Rottenberger EUSTACH-1, April/May 1999, and LBA-EUSTACH-2, et al., 2008]. Such a strategy, by the plants, could increase September/October 1999) in the Rebio Jaru, an ecological the significance of floodplain areas for atmospheric chemis- reserve 100 km north of Ji-Paraná in the state of Rondô- try. However, the impact of fermentation processes on VOC nia, in southwest Amazonia, during the “wet-to-dry season release under long-term flooding is not known. transition” and “dry-to-wet season transition” periods [Kes- These examples highlight the importance of studying selmeier et al., 2002b]. Here, samples were obtained at the VOC emissions, adaptation, and physiology of key species canopy top close to the potential sources/sinks for these in each one of these six environments, as well as the im- compounds, as well as above the forest. The most prominent portance of comparing a key species which grows in all the VOCs identified in the air during April/May were isoprene, environments. Different key species as well as different ad- formaldehyde, and formic acid, with mixing ratios of each aptation strategies may have a significant influence on the ranging up to several parts per billion (ppb), very similar release of volatile organic compounds that we should know to the Balbina site. Oxidation products of isoprene such as about and understand. methyl vinyl ketone as well as methacrolein ranged around 1 ppb. Total monoterpene concentration was below 1 ppb. 1.2. Volatile Organic Compounds in the Atmosphere This changed at the transition phase from dry to wet in Sep- tember/October. C1-C2 organic acids and C1-C2 aldehydes Numerous biogenic VOC species are released into the exhibited a significant increase up to 17 and 25 ppb, respec- atmosphere, and measuring all those which are relevant to tively, which is thought to result from vegetation fires, as are KESSELMEIER ET AL. 185 the high methanol concentrations. Of high interest, however, [2002], they reported 44 out of 95 examined plant species to were substantial increases in the atmospheric mixing ratios release significant amounts of isoprene of more than 20 μg of biogenic compounds. Isoprene increased up to 30 ppb g–1 h–1 (given as carbon on a dry weight basis). However, it near the crown region and was well above 10 ppb at 10–20 should be noted that the species studied were not randomly m above the forest. Interestingly, monoterpene species de- selected or selected based solely on their local dominance. creased. Such atmospheric measurements give an impres- For example, a large number of Ficus species (all isoprene sion about the variability and concentration of VOCs during emitters) were measured in order to investigate emission the different seasons which are due to the seasonality of the variations within the Ficus genera. Three of the 21 Ficus vegetation emissions, climatologic factors, and anthropo- species probed during both the wet and dry season periods genic influences such as fires. showed higher isoprene emission rates in the dry season by Such results are in close accordance with Guenther et al.