长江中下游典型硅酸盐岩流域自然风化与人类活动影响下的水化学特征——以抚河流域为例

Hydrochemical Characteristics of River in a Representative Silicate Rock Region under Natural Weathering and Anthropogenic Activities——A Case Study of the Fuhe River in the Middle and Lower Reaches of the Yangtze River

抚河汇流于中国第一大淡水湖鄱阳湖,也是长江中下游的重要支流,其河流水化学组成代表了典型的硅酸盐岩地区河流风化特征。本研究于2019年1月对抚河流域进行了系统的采样分析,通过离子的主成分分析、离子比值分析等方法对流域河水水化学空间变化、控制因素和主要离子来源进行了研究。结果表明,K^(+)、Na^(+)和HCO_(3)^(-)为抚河流域水体的主要阳离子和阴离子,分别占总阳离子和总阴离子的67.0%和61.4%。TDS平均值为49.51 mg/L,低于世界河流平均值。控制流域水化学特征的主要因素是硅酸盐岩风化,同时也受降雨补给和水分蒸发的影响,其中海洋来源占总的河流比例为7.35%。Cl^(-)、HCO_(3)^(-)、SO_(4)^(2-)主要受农业化肥、工业污染及市政排放等影响,且不同地段的来源具有显著差别。由上游至下游,河流水化学中SO_(4)^(2-)、Cl^(-)不断增加,表明受人类活动的影响较大。

The Fuhe River is an important tributary of the Middle and Lower Reaches of Yangtze River and flows into the Poyang Lake,which is the largest freshwater lake in China.Hydrochemical composition of the Fuhe River represents a typical silicate rock area.The water samples from the main stream and the tributaries were systematically collected in January 2019 and were subjected to the analysis of the spatial variations of hydrochemistry,controlling factors and main ion sources by methods such as the principal component analysis and the ion ratio analysis.The results showed that the main cation and anion in runoffs were K^(+),Na^(+)and HCO_(3)^(-),that accounted for 67%and 61.4%of total cation and anion ions respectively.The average TDS value(49.51 mg/L)is lower than the world average.Chemical weathering of silicate rocks is the primary factor that controls the characteristics of the water,rainfall and water vaporization are another influencing factors,in which,water from seawater was estimated to contribute 7.35%of total river hydrochemistry.Cl^(-),HCO_(3)^(-)and SO_(4)^(2-)in Fuhe basin are mainly derived from agricultural effluent,industrial pollution and municipal sewage,with different shares of these inputs at different parts of the river.The increase of SO_(4)^(2-)and Cl^(-)in water from the upstream to the downstream indicates that anthropogenic activities have a significant impact on the river water chemistry.