长江水系河水主要离子化学特征

2007年夏季采集了长江从上游沱沱河至入海口的干流原水样品36个,长江各主要支流水样品40个,分析了江水Ca2+、Mg2+、Na+、K+、HCO3-、SO42-、Cl-离子含量及溶解性SiO2等溶质成分。结果显示,长江流域水系离子化学组成主要受碳酸盐和蒸发岩风化控制,长江上游水离子化学呈现阳离子以K+和Na+为主,阴离子以Cl-和SO42-为主的蒸发岩类风化控制特征,但随着采样点位下移,离子含量逐渐呈现阳离子以Ca2+为主,阴离子以HCO3-为主的逐渐向碳酸盐风化过渡的特征;从时间变化上看,与20世纪50年代至1990年长江水离子化学数据相比,以Na+、K+、SO42-和Cl-为代表的所有阴阳离子均有明显增加;从通量上看,洞庭湖和鄱阳湖是长江离子两个最大的输入源,除洞庭湖和鄱阳湖外的其他长江各大支流中,岷江是长江Na+、K+、Ca2+、Mg2+、F-和HCO3-的最大输入源,嘉陵江是SO24-和溶解性SiO2的最大输入源;在几大世界河流中,长江是对海洋Mg2+、SO24-和Cl-的输入通量最大的河流,Ca2+和HCO3-通量仅次于亚马逊河。

Major ion chemistry in the Yangtze River

36 water samples were collected in the main Yangtze River channel and 40 in its tributaries.Concentrations of Ca2+,Mg2+,Na+,K+,HCO-3,SO_4-(2-),Cl-and SiO2 in the water samples were determined.It was found that the chemistry of the Yangtze River is dominated by the weathering of carbonates and evaporites with high K+,Na+,Cl-and SO_4-(2-)concentrations in the upstream of the Yangtze River,i.e.Tuotuohe,Tongtianhe and Jinshajiang,and Ca2+ and HCO-3 dominating the cations and anions in the middle and lower stream of the Yangtze River;All the major ions in Yangtze River water,especially Na+,K+,SO_4-(2-)and Cl-,have increased significantly compared with data acquired from 1950s to 1990;Dongting Lake and Poyang Lake are the first two ion sources of the main Yangtze River channel.Besides the two lakes,the Minjiang River is the first source for Na+,K+,Ca2+,Mg2+,F-and HCO-3,and the Jialing River is the first source for SO_4-(2-)and dissolved SiO2;the Yangtze River is the biggest source of Mg2+,SO_4-(2-)and Cl-for the ocean,and its fluxes for Ca2+ and HCO-3 is next to the Amazon River.