鄱阳湖流域乐安河水化学特征及影响因素

Hydrochemical Characteristics and Influencing Factors in the Le'an River, Poyang Lake Basin

通过在2016年12月和2017年7月采集乐安河水样30个,检测了水化学离子、营养盐和溶解态重金属浓度等22项水化学指标,运用多元统计分析方法对河流水化学特征及影响因素进行分析。结果表明:乐安河水化学类型空间差异明显,上游为HCO_3-Ca型水,中游为SO_4-Mg-Ca型水,下游转为SO_4-Ca-Na型水;上游水化学离子主要受岩石风化控制,中、下游受人类活动控制。营养盐浓度中、下游高于上游,中、下游之间差异不明显;枯水期平均浓度高于丰水期;NH_4^+-N、TP在部分采样点超出中国地表水Ⅲ类水质标准。重金属浓度在中、下游之间差异不显著。乐安河水化学特征的主要影响因素为:NH_4^+-N、Cl^-受城市污水影响;Cr、Cu、Zn、Fe、Pb、SO_4^(2-)主要受工矿活动影响;NO_3^--N受城市污水、农业施肥和矿山活动共同影响;TP丰水期影响因素复杂,可能是受土壤可溶性有机物与农业施肥影响,枯水期受城市污水影响。以上研究结果可为流域水环境保护提供参考依据。

In this study, a total of 30 water samples(15 samples in each season) in Le’an River(Poyang Lake Basin, Jiangxi Province, China) were collected in December 2016(dry season) and July 2017(wet season) separately. Twenty-two physicochemical characteristics were analyzed, those included major ions, nutrients, and dissolved heavy metals, etc. Multivariate Statistical Analysis was used to analyze the hydrochemical characteristics and influencing factors. The results indicated that hydro-chemical types were different in three sections of the Le’an River, those were HCO3-Ca type in the upstream, SO4-Mg-Ca type in the midstream, and SO4-Ca-Na type in the downstream. The water chemical ions in the upstream were controlled by natural weathering of rock, while those in the midstream and downstream were most affected by anthropogenic activities. The concentrations of nutrients in the midstream and downstream water were higher than those from upstream water, while those nutrients had no significant differences between the midstream and downstream water. Additionally, the concentrations of nutrients in the dry season were higher than those in the wet season, and the concentrations of NH4+-N and TP in several water samples were higher than China’s surface water Ⅲ quality standards. No significant difference of the dissolved heavy metals concentrations was observed between the midstream and the downstream waters. The main influencing factors of hydrochemical characteristic in the Le’an River were as follows: NH4+-N and Cl- were affected by urban sewage;Cr, Cu, Zn, Fe, Pb and SO42-were mainly attributed to industrial and mineral activities;NO3--N were affected by urban sewage, agriculture and mining activities jointly. The influencing factors of TP were complex in the wet season, which may be affected by soil soluble organic matter and agricultural fertilization, and in the dry season, the urban sewage was the main factor of TP. The results in this study could provide reference for the Poyang Lake Basin environmental protection.