长江流域主要干/支流水化学特征及外源酸的影响

为了探究人类活动对长江流域水化学特征的影响，本文以流域内主要干/支流代表断面的采样点为研究对象，分别于2016年丰水期和平水期采集地表水样各13组，通过离子比值法、主成分分析法和化学离子平衡计算法，综合分析水化学特征，并估算碳酸和外源酸参与碳酸盐岩的溶蚀比例.结果表明，水化学类型主要为HCO₃-Ca型，指示流域内水化学的主要影响因素为碳酸盐岩的溶解，在碳酸盐岩风化过程中，碳酸与碳酸盐岩的相对快速风化为主导反应.此外，丰水期和平水期各采样点碳酸溶蚀比例均值分别为60.33%和59.14%，不同采样点的溶蚀比例差值较大，指示外源酸对河流与岩石侵蚀风化过程的影响不容忽视，且阳离子交换对水化学有一定影响，但并不是主要的反应过程.与多年前水文监测初期的数据相比，硫酸和硝酸对岩石风化作用加强，人为因素对长江的水质影响增大.

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.