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


  • Loubet Benjamin
  • Buysse Pauline
  • Gonzaga-Gomez Lais
  • Lafouge Florence
  • Ciuraru Raluca
  • Decuq Céline
  • Kammer Julien
  • Bsaibes Sandy
  • Boissard Christophe
  • Durand Brigitte
  • Gueudet Jean-Christophe
  • Fanucci Olivier
  • Zurfluh Olivier
  • Abis Letizia
  • Zannoni Nora
  • Truong François
  • Baisnée Dominique
  • Sarda-Estève Roland
  • Staudt Michael
  • Gros Valérie


  • Volatile Organic Compound
  • Air Pollution
  • Winter wheat field

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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 (C 6 H 4 O), a compound not previously reported to be strongly emitted by crops. The average summed VOC emissions were about 173 ± 6 µg m 2 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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