As part of the NSF's continuing program in Global Tropospheric Chemistry, this three-year research project will investigate key mechanisms which couple the trace gas chemistry of the atmosphere to the biosphere and to the atmospheric hydrological cycle. The investigations of biospheric/atmospheric interactions will focus on the cycle of photochemical oxidants in the atmosphere. Using the resistance formulation to simulate the mass transfer and deposition of atmospheric oxidants (eg., O3, H2O2) to mesophyllic leaf cells, this research will attempt to identify the key chemical and physical processes which control the rate of removal of atmospheric oxidants by dry deposition as well as the degree of sensitivity of a plant to damage from the deposition of these atmospheric oxidants. In a related study a one-dimensional photochemical model will be used to study the role of biogenic emissions of hydrocarbons in controlling the levels of atmospheric oxidants in pristine and polluted continental environments. The investigations relating to the hydrological cycle will focus on the processes which control the removal and chemical conversion of soluble trace species by clouds and the development of algorithms to simulate these processes in three- dimensional, chemical transport models of the global troposphere.
