[Major Ionic Features and Their Controlling Factors in the Upper-Middle Reaches of Wujiang River].

ABSTRACT

The Wujing River, the largest river in Guizhou Province, is one of the most important water resources for social and economical development. Recently, with the fast population proliferation and rapid economic growth, the drainage basin is intensively interfered by anthropogenic activities. The hydrochemistry of surface water was analyzed from the upper-middle reaches of Wujiang River for investigating the hydrochemical characteristics and their main influencing factors. The results showed that the major cations of the four rivers were Ca²âº and Mg²âº, accounting for more than 70%, and the main anions were HCO3⁻ and SO4²â», occupying more than 85%. The hydrochemical characteristics in the four rivers were found to be of HCO3-Ca type, and mainly determined by the carbonate rock dissolution, while only a small proportion of them were of HCO3 · SO4-Ca type, reflecting the influence of SO4²â» from anthropogenic activities. Compared to hydrochemical data in 1999, there was an obvious increase in cations and anions concentrations, majorly in NO3⁻, SO2- ion concentrations, which were significantly affected by human activities. The Na⁺, K⁺ , Cl⁻ in the river mainly came from atmospheric precipitation, and Ca²âº, HCO3⁻, Mg²âº, mainly came from carbonate rocks dissolution, while NO3⁻ and SO4²â» mainly came from human activities. According to principal component analysis and correlation analysis, hydrochemical composition of Liuchong River was affected by human activity, and that in the upstream of Sancha River was controlled by atmospheric precipitation and the dissolution of carbonate rocks, that to the downstream was enhanced by human activities. The main ion of Maotiao River was controlled by atmospheric precipitation and carbonate rocks dissolution, and also affected by human activity. The Nanming River, the Qingshui river's tributary, was mainly affected by human activity, while the middle and lower reaches of Qingshui River were affected by both the atmospheric precipitation and human activity.