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Article Dans Une Revue Proceedings of the National Academy of Sciences of the United States of America Année : 2016

Isoprene photochemistry over the Amazon rainforest

Yingjun Liu
  • Fonction : Auteur
Matthew R Dorris
  • Fonction : Auteur
Jean C Rivera-Rios
  • Fonction : Auteur
Roger Seco
  • Fonction : Auteur
Kelvin H Bates
  • Fonction : Auteur
Sergio G Duvoisin
  • Fonction : Auteur
Frank N Keutsch
  • Fonction : Auteur
Saewung Kim
  • Fonction : Auteur
Allen H Goldstein
  • Fonction : Auteur
Alex B Guenther
  • Fonction : Auteur
Antonio O Manzi
  • Fonction : Auteur
Rodrigo a F Souza
  • Fonction : Auteur
Stephen R Springston
  • Fonction : Auteur
Thomas B Watson
  • Fonction : Auteur
Karena A Mckinney
  • Fonction : Auteur
Scot T Martin
  • Fonction : Auteur

Résumé

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 (HO 2) 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 an-thropogenic 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 HO 2 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. isoprene photochemistry | Amazon | organic hydroperoxides
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Dates et versions

hal-01836099 , version 1 (12-07-2018)

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Yingjun Liu, Joel Brito, Matthew R Dorris, Jean C Rivera-Rios, Roger Seco, et al.. Isoprene photochemistry over the Amazon rainforest. Proceedings of the National Academy of Sciences of the United States of America, 2016, 113 (22), pp.6125 - 6130. ⟨10.1073/pnas.1524136113⟩. ⟨hal-01836099⟩

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