Sulfur deposition in Asia: Seasonal behavior and contributions from various energy sectors

Sulfur transport and deposition in Asia, on an annual and seasonal basis, is analyzed using the ATMOS model. Calculations are performed for two complete years (1990 and 1995). Deposition amounts in excess of 0.5 g S m(-2) yr(-1) are estimated for large regions in Asia, with values as high as 10 g S m(-2) yr(-1) in southeastern China. Annual averaged SO2 concentrations in excess of 20 mug SO2 m(-3) are calculated for many urban and suburban areas of eastern China and S. Korea, with an average of 5 mug SO2 m(-3) over most of the emitter regions. Sulfur deposition by major source categories is also studied. Southeast Asia (Indonesia, Malaysia, Philippines, Singapore) receives similar to 25% of its sulfur deposition from shipping activities. Sulfur deposition from bio-fuel burning is significant for most of the underdeveloped regions in Asia. Volcanoes are a major source of sulfur emissions in the Pacific Ocean, Papua New Guinea, Philippines and Southern Japan. Sulfur deposition is shown to vary significantly throughout the year. The monsoons are found to be the largest factor controlling sulfur transport and deposition in the Indian sub-continent and Southeast Asia. India receives over 35% of its total deposition during the summer months. In East Asia, sulfur deposition is estimated to be 10% higher during summer and fall than winter and spring. Model results are compared with observations from a number of monitoring networks in Asia and are found to be generally consistent with the limited observations.