By means of this award, the Inorganic, Bioninorganic, and Organometallic Chemistry Program and the Atmospheric Chemistry Program provide support for an interdisciplinary project on sources of atmospheric nitrous oxide. The work will be carried out by Dr. William C. Trogler and Dr. Mark H. Thiemens of the Chemistry Department of the University of California at San Diego. They will examine the mechanism of decomposition of ammonium nitrate, the reaction of hydroxylamine and nitric oxide, and other reactions by which nitrous oxide might be produced. The influence of aerosols and particulates on these processes will also be investigated. The means of elucidating the reaction mechanism, as well as linking the nitrous oxide produced by various reactions to nitrous oxide in the atmosphere, will be isotopic labeling of nitrogen and oxygen. %%% The concentration of atmospheric nitrous oxide has been increasing in recent years, but the sources of this increase are not well understood. Trogler and Thiemens will investigate the details of nitrous oxide production from various reactions that model potential environmental sources. Trogler's expertise in reaction mechanisms, catalysis, and photochemistry, and Thiemens' in gas phase kinetics and mass spectrometry will be helpful in this collaborative effort to examine these reactions under relevant conditions. Nitrous oxide is a greenhouse gas and is also involved in the atmospheric ozone balance.