MATHEMATICAL-MODELING AND CONTROL OF THE DRY DEPOSITION FLUX OF NITROGEN-CONTAINING AIR-POLLUTANTS

An Eulerian grid-based air quality model has been modified to include a resistance-based dry deposition code. The magnitude and spatial distribution of the dry deposition flux of nitrogen-containing pollutants to the surface of the Los Angeles area was calculated as a function of land use. For August 1982 base case conditions, the dry deposition flux was 247 t of N per day (5 from NO, 49 from NO2, 7 from PAN, 101 from HNO3, 59 from NH3, and 26 from NH4NO3), which corresponds to more than half of the daily NO(x) emissions to the local atmosphere. The effects of emission controls on NO(x) and hydrocarbon sources in Southern California as they existed in 1982 were examined. At the highest level of control studied (37% reactive hydrocarbon reduction, 61 % NO(x) reduction), the nitrogen dry flux would be 174 t of N per day after control (2 from NO, 20 from NO2, 7 from PAN, 58 from HNO3, 75 from NH3, and 12 from NH4NO3).