Volatile organic compound fluxes over a winter wheat field by PTR-Qi-TOF-MS and eddy covariance

Autor: B. Loubet, P. Buysse, L. Gonzaga-Gomez, F. Lafouge, R. Ciuraru, C. Decuq, J. Kammer, S. Bsaibes, C. Boissard, B. Durand, J.-C. Gueudet, O. Fanucci, O. Zurfluh, L. Abis, N. Zannoni, F. Truong, D. Baisnée, R. Sarda-Estève, M. Staudt, V. Gros
Jazyk: angličtina
Rok vydání: 2022
Předmět:
Zdroj: Atmospheric Chemistry and Physics, Vol 22, Pp 2817-2842 (2022)
Druh dokumentu: article
ISSN: 1680-7316
1680-7324
DOI: 10.5194/acp-22-2817-2022
Popis: Volatile organic compounds (VOCs) contribute to air pollution through the formation of secondary aerosols and ozone and extend the lifetime of methane in the atmosphere. Tropospheric VOCs originate to 90 % from biogenic sources on a global scale, mainly from forests. Crops are also a potentially large yet poorly characterized source of VOCs (30 % of the VOC emissions in Europe, mostly oxygenated). In this study, we investigated VOC fluxes over a winter wheat field by eddy covariance using a PTR-Qi-TOF-MS with high sensitivity and mass resolution. The study took place near Paris over a 5-week period and included flowering, crop maturity and senescence. We found a total of 123 VOCs with fluxes 3 times above the detection limit. Methanol was the most emitted compound with an average flux of 63 µg m−2 h−1, representing about 52 % of summed VOC emissions on a molar basis (36 % on a mass basis). We also identified ethanol, acetone, acetaldehyde and dimethyl sulfide among the six most emitted compounds. The third most emitted VOC corresponded to the ion m/z 93.033. It was tentatively identified as furan (C6H4O), a compound not previously reported to be strongly emitted by crops. The average summed VOC emissions were about 173 ± 6 µg m2 h−1, while the average VOC depositions were about 109 ± 2 µg m−2 h−1 and hence 63 % of the VOC emissions on a mass basis. The net ecosystem flux of VOCs was an emission of 64 ± 6 µg m−2 h−1 (0.5 ± 0.05 nmol m−2 s−1). The most deposited VOCs were identified as hydroxyacetone, acetic acid and fragments of oxidized VOCs. Overall, our results reveal that wheat fields represent a non-negligible source and sink of VOCs to be considered in regional VOC budgets and underline the usefulness and limitations of eddy covariance measurements with a PTR-Qi-TOF-MS.
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