PHOTOCHEMICAL OXIDANT PROCESSES IN THE PRESENCE OF DUST - AN EVALUATION OF THE IMPACT OF DUST ON PARTICULATE NITRATE AND OZONE FORMATION

The influence of dust on the tropospheric photochemical oxidant cycle is studied through the use of a detailed coupled aerosol and gas-phase chemistry model. Dust is a significant component of the troposphere t hroughout Asia and provides a surface for a variety of heterogeneous r eactions. Dust is found to be an important surface for particulate nit rate formation. For dust loading and ambient concentrations representa tive of conditions in East Asia, particulate nitrate levels of 1.5-11. 5 mug m-3 are predicted, consistent with measured levels in this regio n. Dust is also found to reduce NO(x) levels by up to 50%, HO2 concent rations by 20%-80%, and ozone production rates by up to 25%. The magni tude of the influence of dust is sensitive to the mass concentration o f the aerosol, relative humidity, and the value of the accommodation c oefficient.