Abstract:

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.

Key words: Sulfur isotope/Wujiang drainage basin/ high flow season/cascade reservoirs