The growing contribution of sulfur emissions from ships in Asian waters, 1988-1995

International shipping is a major source of sulfur emissions in Asia. Becau se the fuel oil used by ships is high in sulfur, the resulting emissions of SO2 are large and contribute as much as 20% to the atmospheric loading in the vicinity of ports and heavily traveled waterways. Because of the rapid growth of Asian economies in the 1980s and early 1990s, it is estimated tha t shipping trade grew by an average of 5.4% per year between 1988 and 1995; in particular, crude oil shipments to Asian countries other than Japan gre w by an average of 11.4% per year. The emissions of SO2 from shipping are e stimated to have grown by 5.9% per year between 1988 and 1995, rising from 545 Gg in 1988 to 817 Gg in 1995. This study uses the ATMOS atmospheric tra nsport and deposition model to study the effects of these emissions, both i n absolute terms and relative to land-based emissions, on wet and dry depos ition of sulfur. Southeast Asia is most heavily affected by emissions from ships, particularly Sumatra, peninsular Malaysia, and Singapore, which rout inely receive in excess of 10% of their deposition from ships. A strong sea sonal component is also observed, with large areas of Southeast Asia and co astal Japan receiving sulfur deposition that exceeds 10 mg S m(-2) season(- 1). Deposition is at least 25% higher in summer and fall than in winter and spring. Peak values of 25-50 mg S m(-2) season(-1) are calculated for wint er in the Strait of Malacca. This work suggests a need to introduce policie s to reduce the sulfur content of marine fuels or otherwise reduce emission s of SO2 from ships in Asian waters. (C) 2000 Elsevier Science Ltd. All rig hts reserved.