[Water Chemical Characteristics and Influence of Exogenous Acids in the Yangtze River Basin]

To explore the influence of human activities on the Yangtze River water chemistry, water samples were obtained from a representative section the main river stem/branch in wet and normal seasons in 2016. Ion ratio analysis, principal component analysis(PCA), and chemical ion balance calculations were performed, and carbonate rock dissolution rates were determined based on carbonate and exogenous acids. The result show that HCO₃-Ca is the dominant hydrochemistry type, indicating that the dissolution of carbonate rocks in the basin is the main process affecting hydrochemistry, and carbonate acid is significant in the weathering of carbonate rocks. In addition, the proportion of carbonate acid dissolution in the wet and normal seasons accounted for 60.33% and 59.14% of the total dissolution, respectively. The dissolution ratio among the different sampling points was notable, which indicates that the carbon sink effect of exogenous acid cannot be ignored. In addition, cation exchange some influence on hydrochemistry but was not the main reaction process. Compared with hydrological monitoring data for the last few years, the weathering of rocks by sulfuric and nitrate acids has strengthened, and the negative effects of anthropogenic pollution in the Yangtze River have increased.