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Abstract:
We have carried out a study on the variation of strontium isotope composition of river waters, Wujiang and Yuangjiang River, in karst areas of Guizhou Province, China. The results obtained permit us to characterize the geochemistry of the river draining karst terrain and obtain a better understanding of main controls of catchment geology, chemical weathering of different rocks, and evaluate impact of human activities on the environment. The isotopic ratios of dissolved Sr in all rivers are between Sr-87/Sr-86 = 0.7077 and 0.7110, totally lower than the weighted average of Sr-87/Sr-86 = 0.7119 for the world large rivers. The Wujiang River waters have Sr concentrations from 1.0 to 6.1 mu mol/L, while the Yuanjiang River waters have much lower Sr concentrations ranging from 0.28 to 1.3 mu mol/L. Most of the river waters from the Wujiang river are characterized by low Ca/Sr and Mg/Sr, and Sr-87/Sr-86 ratios, in which a majority of river waters are of Sr-87/Sr-86 ratios lower than the average Sr isotope ratio (Sr-87/Sr-86 = 0.709) of present seawater. The higher Sr-87/Sr-86 ratios are observed in the river waters in the lower reach of the Wujiang River, where the lithology is dominated by detrital rocks and dolomite. The water from Yuanjiang River show higher Ca/Sr, Mg/Sr and Sr-87/Sr-86 ratios due to weathering of silicates, as compared to the river waters from Wujiang river