丰水期乌江上游干流水库-河流体系硫同位素组成

2007年7月对乌江上游河流、乌江干流上的3座不同库龄的梯级水库（洪家渡水库、东风水库、乌江渡水库）表层及垂直剖面水体的可溶性硫酸盐的硫同位素组成进行了研究。在垂直剖面上，洪家渡水库硫同位素值（δ34S）介于+03‰~+31‰，下泄水为-07‰；东风水库δ34S值介于-75‰~-55‰，下泄水为-68‰；乌江渡水库δ34S值介于-43‰~-06‰，下泄水为-29‰。上述结论表明，硫同位素组成变化反映了水库硫的不同来源及生物地球化学过程。不同水库表层和垂直剖面水体的硫同位素平均值有差别，水库表层的硫同位素比值主要受输入水体的控制，垂直剖面由表层向下硫同位素比值偏负，主要是由于生物作用以及有机硫的氧化造成的。

SULFUR ISOTOPE COMPOSITION OF RIVER CHANNEL AND RESERVOIR WATER IN UPPER REACHES OF WUJIANG RIVER IN HIGH FLOW SEASON

The compositions of sulfur isotopes were investigated in cascade reservoirs with different running ages (Hongjiadu Reservoir, Dongfeng Reservoir and Wujiangdu Reservoir) along Wujiang River. Water samples in the front of dams were collected along water column, and other river water samples were collected at 0.5m below water surface in July, 2007. The sulfur isotopic compositions (δ34S) along water column varied from +0.3‰ to +3.1‰ in Hongjiadu Reservoir, -7.5‰ to -5.5‰ in Dongfeng Reservoir, and -4.3‰ to -0.6‰ in Wujiangdu Reservoir, respectively. The δ34S in the release water of these three reservoirs were -0.7‰, -6.8‰, and -2.9‰, respectively. The results indicate that the changes in sulfur isotopic compositions mainly reflect the biogeochemical processes and the different sources of sulfur entering into reservoirs. Sulfur isotopic compositions in surface water and along water column showed a variation in different reservoirs. The δ34S in surface layer was controlled by the sulfur isotopic compositions of the input water, while the δ34S along water column decreased with the increase in depth, reflecting an influence of biological function and organic sulfur oxidation.