Acid deposition in central Japan

Abstract

Acid deposition at the inland mountainous regions of central Japan is investigated using the STEM-II model. Previous studies of the long range transport of pollutants in central Japan have focused on the production and transport of photochemical oxidants. Highly polluted air is found in the central mountainous areas late in the afternoon on clear summer days, resulting from the transport of pollutants from the Tokyo Metropolitan area. The impact of this LRT on acid deposition at these inland regions is evaluated by simulating a series of hypothetical storms under LRT conditions. Nitrate and SO 4 2− concentrations in the rain water in excess of 100 micromolar are predicted and the total wet deposition of NO 3 − exceeds that of SO 4 2− by a factor of 2. The wet deposition during evening storms is nearly 100% higher than that during afternoon storms. Simulations with 50% reductions in NO x and SO x emissions decrease the wet deposition of NO 3 − and SO 4 2− by ∼40 and ∼15%, respectively.