An assessment of sulfur deposition pathways in Asia

The acid deposition model is developed and applied to assess the sulfur deposition pathways in Asia. Simulations for four seasons are conducted: February, April, August, and October. The predicted results of summer and winter are compared to measured concentration of SO2, sulfate, and sulfate wet deposition in Japan. Further comparison of sulfate wet deposition to observations in China is made to assess the general performance of the model. The study shows that wet deposition is more important than dry deposition. It is the predominant factor in each of these four months. It is also found that rainout process, compared to washout process, make a larger contribution to sulfate wet deposition in summer and spring than in the dry months, such as October. The total sulfur wet to dry deposition ratio is 1.6 in February, 1.2 in April, 2.9 in August, and 1.9 in October.