CONTROLS ON THE MAJOR ION CHEMISTRY OF THE URUMQI-RIVER, TIAN-SHAN, PEOPLES-REPUBLIC-OF-CHINA

Water and snow samples were collected in May of 1990 and 1992 in headw ater basins and along a longitudinal transect of the Urumqi River, loc ated in northwestern China. Surface waters were dominated by Ca2+ and HCO3- at all sites. Maximum measured SO42- concentrations in surface w aters were 550 mu eq L(-1), and were balanced by Ca2+ and HCO3-; pH wa s slightly alkaline at all locations, Several independent analyses eac h concluded that the solute composition of surface waters was dominate d by dissolution of rocks with rapid weathering kinetics, such as calc ite and dolomite, Preliminary analysis of stable sulfur ratios in head water basins shows delta(34)S values of +6.8 for snow and +3.3 for sur face waters. Changes in the delta(34)S value of surface waters with in creasing basin area were variable, suggesting changes in the stable su lfur ratios of source materials. The large amounts of HCO3- and base c ations at all sites indicates that the Urumqi River is not sensitive t o acidification from atmospheric deposition.