近年来长江口水体主离子的变化特征及影响因素分析

通过对2004-2008年长江口徐六泾江水样品中主要离子(Ca2+,Mg2+,Na+,K+,HCO32-,SO42-,Cl-,NO3-和SiO32-)含量的月观测,以及对2008年9月长江下游调查,研究发现,长江河口水体主要离子浓度与径流呈现很好负相关关系,季节变化明显,但主离子浓度季节差异小于径流量的季节差异.河口水体中K+,Na+,Ca2+,Mg2+,Cl-,SO42-,NO3-,总硬度/总碱度有上升趋势,尤其以SO42-和总硬度/总碱度的上升趋势显著,SiO32-,HCO3-则表现出下降趋势.引起近年来长江口水体主离子浓度变化的影响因素为工业排放、环境酸化、循环盐和三峡蓄水等.

Change characteristics of major ions and their influence factors in Yangtze Estuary in recent years

The geochemistry of major ions(Ca~(2+),Mg~(2+),Na~+,K~+,HCO_3~(2-),SO_4~(2-),Cl~-,NO_3~- and SiO_3~(2-))in the Yangtze River was studied, based on the monthly monitoring data at Xuliujing station for the period of 2004-2008 and the investigation result of the Yangtze River in September 2008.The study found that the concentration of main ions varies clearly in different seasons, with a negative correlation with the discharge of the River.But the difference of the concentration is less clearly than that of the discharge.There is a persistently increasing in the concentrations of K~+, Na~+, Ca~(2+), Mg~(2+), Cl~-, NO_3~-, SO_4~(2-) and the ratio of hardness/alkalinity;especially the concentration of SO_4~(2-) and the ratio of hardness/alkalinity have a more obvious increasing trend.In contrast, the concentration of SiO_3~(2-) and HCO_3~- show a decreasing trend.The changes of major ions mainly result from the environment acidification, the pollution emissions by human, the cyclic salt from sea, the preserved effect by reservoirs establishments etc.