Characteristics and driving factors of surface water chemistry of Wujiang watershed

The changes in the water chemistry of rivers can reflect influence of anthropogenic activities on the water environment to some extent. To understand the relationship between the spatial distribution of the eco-environment of the watershed and the characteristics of water chemistry and geochemistry of rivers, firstly, the digital Wujiang watershed was built, and then the sub-watersheds were delineated, taking the sample points as sub-watershed outlets based on GIS. Secondly, using the function of spatial analyst of GIS, the statistical features of eco-environment (such as lithology and land use/cover) of each sub-watershed were calculated according to their respective classification. Finally, the correlation between the spatial distribution of lithology of the sub-watersheds and their corresponding ⁸⁷Sr/⁸⁶Sr ratio of river water, the correlation between NO₃ ⁻/HCO₃ ⁻, Cl⁻/HCO₃ ⁻, SO₄ ²⁻/HCO₃ ⁻ and anthropogenic activities, respectively, and the correlation between the fraction of green vegetation of the sub-watershed and their corresponding flux of TDS (total dissolved solids) were analyzed quantitatively. The results justify that the ⁸⁷Sr/⁸⁶Sr ratio of river water is highly dependent on the lithologic feature of the watershed and indicate that anthropogenic activities are one of the main sources of NO₃ ⁻ and SO₄ ²⁻ of river waters. The output of TDS is highly dependent on the percentage of vegetation cover of the watershed.