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Title: Observations of sesquiterpenes and their oxidation products in central Amazonia during the wet and dry seasons
Authors: Yee, Lindsay D.
Isaacman-VanWertz, Gabriel A.
Wernis, Rebecca A.
Meng, Meng
Rivera, Ventura
Kreisberg, Nathan M.
Hering, Susanne V.
Bering, Mads S.
Glasius, Marianne
Upshur, Mary Alice
Gray Bé, Ariana
Thomson, Regan J.
Geiger, Franz M.
Offenberg, John H.
Lewandowski, Michael
Kourtchev, Ivan N.
Kalberer, Markus
Sá, Suzane S. de
Martin, Scot T.
Alexander, Michael Lizabeth
Palm, Brett B.
Hu, Weiwei
Campuzano-Jost, Pedro
Day, Douglas A.
Ji?enez, José Luis
Liu, Yingjun
McKinney, Karena A.
Artaxo, Paulo
Viegas, Juarez
Manzi, Antônio Ocimar
Oliveira, Maria B.L.
Souza, Rodrigo Augusto Ferreira de
Machado, Luiz Augusto Toledo
Longo, Karla Maria
Goldstein, Allen H.
Keywords: Aerosol
Dry Season
Source Apportionment
Volatile Organic Compound
Wet Season
Issue Date: 2018
metadata.dc.publisher.journal: Atmospheric Chemistry and Physics
metadata.dc.relation.ispartof: Volume 18, Número 14, Pags. 10433-10457
Abstract: <p>Biogenic volatile organic compounds (BVOCs) from the Amazon forest region represent the largest source of organic carbon emissions to the atmosphere globally. These BVOC emissions dominantly consist of volatile and intermediate-volatility terpenoid compounds that undergo chemical transformations in the atmosphere to form oxygenated condensable gases and secondary organic aerosol (SOA). We collected quartz filter samples with 12 h time resolution and performed hourly in situ measurements with a semi-volatile thermal desorption aerosol gas chromatograph (SV-TAG) at a rural site (<q>T3</q>) located to the west of the urban center of Manaus, Brazil as part of the Green Ocean Amazon (GoAmazon2014/5) field campaign to measure intermediate-volatility and semi-volatile BVOCs and their oxidation products during the wet and dry seasons. We speciated and quantified 30 sesquiterpenes and 4 diterpenes with mean concentrations in the range 0.01-6.04 ng mĝ'3 (1-670 ppqv). We estimate that sesquiterpenes contribute approximately 14 and 12 % to the total reactive loss of O3 via reaction with isoprene or terpenes during the wet and dry seasons, respectively. This is reduced from ĝ1/4  50-70 % for within-canopy reactive O3 loss attributed to the ozonolysis of highly reactive sesquiterpenes (e.g., <i>β</i>-caryophyllene) that are reacted away before reaching our measurement site. We further identify a suite of their oxidation products in the gas and particle phases and explore their role in biogenic SOA formation in the central Amazon region. Synthesized authentic standards were also used to quantify gas- and particle-phase oxidation products derived from <i>β</i>-caryophyllene. Using tracer-based scaling methods for these products, we roughly estimate that sesquiterpene oxidation contributes at least 0.4-5 % (median 1 %) of total submicron OA mass. However, this is likely a low-end estimate, as evidence for additional unaccounted sesquiterpenes and their oxidation products clearly exists. By comparing our field data to laboratory-based sesquiterpene oxidation experiments we confirm that more than 40 additional observed compounds produced through sesquiterpene oxidation are present in Amazonian SOA, warranting further efforts towards more complete quantification. © 2018 Author(s).
metadata.dc.identifier.doi: 10.5194/acp-18-10433-2018
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