大坝拦截对河流水溶解组分化学组成的影响分析——以夏季乌江渡水库为例

以乌江渡水库为主要研究对象，揭示了大坝拦截条件下的夏季水化学特征：阴离子以HCO-3,SO2-4为主，阳离子以Ca2+,Mg2+为主，其余离子含量低于10%，说明了碳酸盐岩的风化对水体化学组成起到了主要控制作用，蒸发盐岩石的风化对水体化学组成影响较小。水库水体存在温度分层现象，形成了不同层位的水体有着不同的水化学组成，即水化学分层。水化学的分层形成了溶解组分在水库垂直深度上的规律分布，比如受藻类的影响，Si和叶绿素随深度成相反的变化特征；HCO-3受光合作用和有机质降解的影响，30 m 以上随着水深的增加而递增，30 m 以下呈现相反趋势；水库泄水方式明显改变了水化学各种参数和离子在水体中的分配。乌江水库两主要支流（息烽河和偏岩河）分别对乌江渡坝前水体中的Ca2+,SO2-4,HCO-3,Mg2+和K+,Na+,Cl-有贡献。网箱养鱼、生活污水、农业施肥、酸性矿山废水以及酸雨沉降都会对水体造成不同程度的污染。

DAMMING EFFECT ON WATER DISSOLVED CHEMISTRY COMPONENTS ——A CASE STUDY OF WUJIANGDU RESERVOIR WATER IN SUMMER, SOUTHWEST CHINA

This study investigated the water chemistry of Wujiangdu Reservoir and its response to river damming.Results showed that major ionic chemistry of the reservoir dominated by HCO-3,SO2-4,Ca2+ and Mg2+,which account for about 90% of the total solutes in the water.It is concluded that limestone weathering,among silicate rock and evaporation weathering,are the most important controls on the water chemistry.The reservoir showed clear temperature stratification,and hence induced different chemical composition of major ions in the water of different water layers.Accordingly,dissolved components appeared different distribution characteristics along the water column.Si and Chlorophyll showed a negative correlation with each other in the vertical profile,due to biological function such as algal absorption.Concentration of HCO-3 decreased from surface water to 30 m in depth and then increase downwards,controlled by both photosynthesis and organic decomposition.River damming and the ways of water discharge of the reservoir can change the water chemistry of the reservoir and discharged water.In Pianyan River and Xifeng River Ca2+,SO2-4,HCO-3 Mg2+,K+,Na+ and Cl- have contributions to Wujiangdu Reservoir.Fish feeding,sewage inputs,fertilizer use and acid rain deposition are the possible contaminant sources for the reservoir water.