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Nature

Title:		Atmospheric oxidation capacity sustained by a tropical forest
Author(s):		Lelieveld J; Butler TM; Crowley JN; Dillon TJ; Fischer H; Ganzeveld L; Harder H; Lawrence MG; Martinez M; Taraborrelli D; Williams J;
Address:		"Max Planck Institute for Chemistry, 27 Becherweg, 55128 Mainz, Germany. lelieveld@mpch-mainz.mpg.de"
Journal Title:		Nature
Year:		2008
Volume:		452
Issue:		7188
Page Number:		737 - 740
DOI:		10.1038/nature06870
ISSN/ISBN:		1476-4687 (Electronic) 0028-0836 (Linking)
Abstract:		"Terrestrial vegetation, especially tropical rain forest, releases vast quantities of volatile organic compounds (VOCs) to the atmosphere, which are removed by oxidation reactions and deposition of reaction products. The oxidation is mainly initiated by hydroxyl radicals (OH), primarily formed through the photodissociation of ozone. Previously it was thought that, in unpolluted air, biogenic VOCs deplete OH and reduce the atmospheric oxidation capacity. Conversely, in polluted air VOC oxidation leads to noxious oxidant build-up by the catalytic action of nitrogen oxides (NO(x) = NO + NO2). Here we report aircraft measurements of atmospheric trace gases performed over the pristine Amazon forest. Our data reveal unexpectedly high OH concentrations. We propose that natural VOC oxidation, notably of isoprene, recycles OH efficiently in low-NO(x) air through reactions of organic peroxy radicals. Computations with an atmospheric chemistry model and the results of laboratory experiments suggest that an OH recycling efficiency of 40-80 per cent in isoprene oxidation may be able to explain the high OH levels we observed in the field. Although further laboratory studies are necessary to explore the chemical mechanism responsible for OH recycling in more detail, our results demonstrate that the biosphere maintains a remarkable balance with the atmospheric environment"
Keywords:		Animals Atlantic Ocean Atmosphere/*chemistry Butadienes/metabolism French Guiana Guyana Hemiterpenes/metabolism Hydroxyl Radical/metabolism Nitric Oxide/metabolism Oxidation-Reduction Ozone/analysis Pentanes/metabolism Suriname Trees/*metabolism *Tropical;
Notes:		"MedlineLelieveld, J Butler, T M Crowley, J N Dillon, T J Fischer, H Ganzeveld, L Harder, H Lawrence, M G Martinez, M Taraborrelli, D Williams, J eng England 2008/04/11 Nature. 2008 Apr 10; 452(7188):737-40. doi: 10.1038/nature06870"