THE sulfur isotopic composition of dissolved sulfate in any rivers has been recognized as a mixture of thesulfur derived from the soil, bedrock and the atmosphere. The measurement of the sulfur isotopic composition in a river water can provide background information on the biogeochemical cycling of sulfur in theriver basin. So far, however, little work has been done on sulfur isotope in the watersheds of the majorrivers of the world. In particular, no information of the sulfur isotope of the major rivers in Asian conti- THE sulfur isotopic composition of dissolved sulfate in any rivers has been recognized as a mixture of the sulfur derived from the soil, bedrock and the atmosphere. The measurement of the sulfur isotopic composition in a river water can provide background information on the biogeochemical cycling of sulfur in So far, however, little work has been done on sulfur isotope in the watersheds of the majorrivers of the world. In particular, no information of the sulfur isotope of the major rivers in Asian conti-