中国东部主要入海河流河口区地球化学特征：理化指标与水溶态元素浓度

Hydrogeochemical characteristics of major estuaries in eastern China:physicochemical indicators and soluble element concentrations of river water

河水理化性质和元素组成特征直接影响到水体利用功能,入海河流元素输送量对近岸海洋生态环境具有重要影响。在中国东部33条入海河流下游河段或河口区布设了水地球化学调查点,分别在2007年夏季(丰水期)、2007年底—2008年初(枯水期)采样并测定了河水酸碱度、电导率值以及溶解态常量和微量元素浓度。研究表明,多数北方河流水体酸碱度、电导率值以及常量元素浓度高于南方河流,与中国土壤及其常量元素组成的南北分带相吻合,反映了我国南北气候分带对河水地球化学特征的控制作用,推断少数河流酸碱度、电导率和常量元素浓度的异常分布与海水混合作用、人为污染等作用有关;部分河流水体中微量元素浓度背离于区域正常浓度,其原因一是与区域地球化学背景有关,二是与城市污染影响有关,通过对比部分城市上、下游水体元素浓度证实城市污染的影响;研究认为丰水期易溶元素Na、Ca、K、Zn、Se浓度较低反映了大量降水的稀释效应,而丰水期河水Al、REE、Fe、Pb、Tl等元素浓度明显高于枯水期,主要与丰水期暴雨形成的地面径流携带大量胶体颗粒进入地表水有关。

Hydro-physicochemical properties and element concentrations of rivers constitute key indicators related to water functions.Chemical flux through river to sea has important impact on marine ecosystem.This paper presents pH values,electric conductivities and soluble concentrations of major and trace elements in river water sampled at the lower position or estuaries of 33 rivers.It is demonstrated that pH values,electric conductivities and soluble concentrations of major and trace elements in most rivers of northern China are much higher than those in rivers of southern China,which is consistent with climate change from north to south.The soluble concentrations of major elements in river water are associated with the zoning of soil type and soil chemical distribution pattern from north to south.However,anomalous content of major elements and physicochemical indexes in some rivers may be influenced by the mixture of sea water with fresh water.It is found that trace element concentrations in some rivers are anomalous in comparison with the concentrations in other rivers of the same region.Such a phenomenon may be attributed to（1） special geological and geochemical background of drainage areas;and（2） anthropogenic activity and pollution.It is inferred that the lower concentrations of soluble Na,Ca,K,Zn,Se in flood season are caused by dilution under higher precipitation,whereas the higher concentration of Al,REE,Fe and some other elements may be the consequence of containing lots of micro-particulates and colloids derived from soil through surface current.