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Tan Y.,Rutgers University | Tan Y.,Carnegie Mellon University | Lim Y.B.,Rutgers University | Altieri K.E.,Princeton University | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2012

Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including pyruvate, oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid plays a central role in the aqueous oxidation of methylglyoxal and it is a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid (20 μM-10 mM) was oxidized by OH radicals, and pyruvic acid and methylglyoxal experimental samples were analyzed using new analytical methods, in order to better understand the formation of SOA from acetic acid and methylglyoxal. Glyoxylic, glycolic, and oxalic acids formed from acetic acid and OH radicals. In contrast to the aqueous OH radical oxidation of methylglyoxal, the aqueous OH radical oxidation of acetic acid did not produce succinic acid and oligomers. This suggests that the methylgloxal-derived oligomers do not form through the acid catalyzed esterification pathway proposed previously. Using results from these experiments, radical mechanisms responsible for oligomer formation from methylglyoxal oxidation in clouds and wet aerosols are proposed. The importance of acetic acid/acetate as an SOA precursor is also discussed. We hypothesize that this and similar chemistry is central to the daytime formation of oligomers in wet aerosols. © 2012 Author(s). Source

Kroeze C.,Wageningen University | Kroeze C.,Open Box | Dumont E.,UK Center for Ecology and Hydrology | Seitzinger S.,International Geosphere Biosphere Programme IGBP
Journal of Integrative Environmental Sciences | Year: 2010

Emissions of nitrous oxide (N2O) from aquatic systems such as rivers and estuaries are enhanced as a result of human activities on land resulting in enhanced nitrogen availability in aquatic systems. These human activities include agricultural activities such as fertilizer use, as well as industrial activities resulting in nitrogen (N) losses to the environment. In this article, we analyze past and future trends in global emissions of N2O from rivers and estuaries. We calculate aquatic N2O emissions from trends in the export of nitrogen to coastal waters by world-wide rivers. These trends in riverine N exports are from the Global NEWS models, which are global, regionally explicit models developed in the NEWS (Nutrient Export from WaterShed) framework. The NEWS models calculate nutrient exports from land to coastal waters, taking into account different human activities on the land, as well as biological N2 fixation and different ways in which nitrogen is retained in watersheds, including the effect of dams. We present global total emissions of N2O for the years 1970, 2000, and for four scenarios for 2050, as well as regional patterns. © 2010 Taylor & Francis. Source

Nobre C.,National Institute for Space Research | Brasseur G.P.,Climate Services Center | Brasseur G.P.,U.S. National Center for Atmospheric Research | Shapiro M.A.,U.S. National Center for Atmospheric Research | And 9 more authors.
Bulletin of the American Meteorological Society | Year: 2010

Biosphere can be called the 'life zone' of Earth system as it plays a vital role in a complex, integrated Earth system prediction framework. The biosphere is composed of living beings and their multi-way interaction with the geophysical and biological elements within the lithosphere, hydrosphere, and atmosphere. The development of integrated prediction systems for the seasonal-to-decadal timeframe must become a major objective of the operational prediction centers with engagement of the academic research community. It is suggested that future efforts in multidisciplinary Earth system modeling should include the development of global Earth system analysis and prediction models that account for physical, chemical, and biological processes in a coupled atmosphere-ocean-land-ice system; the development of a systematic framework that links the global climate and regionally constrained weather systems and the interactions and associated feedbacks with biogeochemistry, biology, and socio-economic drivers. Source

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