| 摘要 | It is important to study water quality and ion chemistry of river under Global Environment Change and human activities. Ion chemistry of river can reflect the nature and characters of drainage rock. To study physical character of controlling of ion formation in drainage is helpful to get to know what influence of human activities produce, such as irrigation, fertilization, mining and industrial production and so on. Components of river such as NO3-, SO42-, As, Al et al can reveal amount of pollution. Therefore，the characters of drainage water can reflect the effec human produces. To study river ion and it’s distribution can develop important information on the chemical weathering of catchment, biogeochemistry cycles and also reveal the exegetic cycles of elements in the continent-river-ocean system. It is also helpful to evaluate the river ion which is influenced by Economic Factors such as population, to protect water resource using river self-purification and environmental effect reasonably, to provide scientific basis for using water resource and controlling pollution.
In this paper, Xijiang River, lower of Huanghe River, upstream of Changjiang River and Huaihe River were sampled. By studying the major elements and trace elements of river water, some conclusions are drawn as follows:
1. pH of Drainage basin of Xijiang River, lower of Huanghe River, upstream of Changjiang River and Huaihe River is 7.40, 8.11, 8.34, 7.95, respectively. Dissolved oxygen of Xijiang River is 7.51 mg/l, lower than of Huanghe River which DO is 8.27 mg/l. The average total dissolved solid of Xijiang River is 152.78 mg/l, lower than of Huanghe River and upstream of Changjiang River. In addition, the total suspend solid of Xijiang River decreases from the headwater to the estuary.
2. The chemical ion composition of the these river water is characterized by dominance of HCO3- and Ca2+. The total flux of the anion in all rivers increases in the following order, HCO3- > SO42 -> Cl- > NO3-. The content of HCO3- of upstream of Huaihe River is highest, and Xijiang River is lowest in all rivers. In ascending order, concentrations of cations in upstream of Changjiang River and Xijiang River can be ordered as Ca2+ > Mg2+ > Na+ > K+. But concentrations of cations in upstream of Huaihe River and lower of Huanghe River increases in the following order Ca2+ > Na+ > Mg2+ > K+.
Weathering of catchment controls the ion composition of these river. But the control of evaporative crystallization increases gradually, from south to north of China in this study. And composition of Huaihe River reflects the transitional character. Pollution discharge is the dominance of Nitrate in all rivers. In addition, the pollution of the Huanghe River is heavier than Xijiang River.
3. The order of concentrations of trace elements in Xijiang River, lower of Huanghe River, upstream of Changjiang and Huaihe River is respectively observed to be: Zn > Cr > Cu > As > Al > Pb >Cd, Zn > Cr > Cu > As > Al > Pb > Cd, Zn>Cr>Pb>As>Cu=Al>Cd， Zn>Cr>As>Pb>Al>Cu>Cd. The average content of Zn and Cd is 37.72μg/l, 0.24μg/l respectively in Xijiang River. The average content of Cu and Cr is 6.12μg/l, 7.61μg/l respectively in Xijiang River, which is higher than other three river catchments. In addition, the average content of dissolved Al is 12.7 μg/l in lower of Huanghe River, which is the highest among these catchments studied. But the average content of dissolved Zn and Al in upstream of Huaihe River is higher.
Elements diifference between water and weathered mantle results from the weathering of catchment, which develops the relative enrichment of Al and As, but relative depletion of Zn, Cu and Cr. In addition, human activities also contributes some to the content of As and Cd in river water.
4. Difference of natural conditions controls the composition of river ion, but human activities’ influence is gradually increasing. Input of pollution of industry and agriculture changes the content of natural river ion, which makes river ion such as NO3-, SO42-, As and Al enriched. Geochemistry behavior of elements in river water is affected by human activities more and more.; 研究人类活动、全球变化对河流水质、离子化学特征及分布的影响具有重要意义。河流离子化学组成可以反映水系的区域岩性，物理化学风化特征。而对于控制河流离子化学自然因素的研究则有助于判别人类活动如农业灌溉施肥、矿山开采、工业生产等对河流的影响。同时，河流组分如NO3-、SO42-、As、Cd等的组成特征可以反映人类活动污染物输入程度。因此，河流水化学特征可以从一定程度上反映人类活动对水环境的影响。同时，研究河水离子化学特征及其分布规律也可以获得化学元素的生物地球化学循环、风化侵蚀及其在陆地—河流—海洋系统循环过程中的重要信息。此外，还有助于评价不同经济因素如人口密度等对河流离子的影响；有助于合理有效的利用河水的自净容量和环境效应，保护水资源；为水资源的开发利用、污染控制提供科学依据。
本文以中国南北方代表性流域—西江流域、长江中游（主要为汉水和乌江水系）、淮河上游及黄河下游流域河水为研究对象，通过对河水主要及微量金属离子的考察，结合基本水质理化参数，初步研究了我国南北方一些河流的离子化学特征及影响因素。通过此次研究，得出以下几点认识：
1. 西江流域河流pH均值为7.40，长江中游为8.11，黄河下游为8.34，淮河上游为7.95。西江流域河流DO含量均值为7.51 mg/l，低于黄河下游干流的8.27 mg/l；黄河下游支流DO含量显著低于干流。西江流域TDS经向分异显著，随经度增加逐渐降低。西江流域TDS平均值为152.78 mg/l，低于长江、黄河水系。
2. 西江流域、长江中游、淮河上游及黄河下游阴离子均以HCO3-平为主，各水系阴离子平均含量顺序均为HCO3- > SO42 -> Cl- > NO3-。研究区域水系中HCO3-平均含量以淮河上游为最高，西江流域最低；SO42 -、Cl-及NO3-平均含量则以黄河下游为最高，长江中游最低。研究区域水系阳离子均以Ca2+为主，西江流域及长江中游阳离子平均含量顺序为Ca2+ > Mg2+ > Na+ > K+，而淮河上游、黄河下游阳离子平均含量顺序则为Ca2+ > Na+ > Mg2+ > K+。
从长江中游到淮河上游、黄河下游，区域岩石风化是控制离子组成的主要因素，但蒸发结晶因素的贡献逐渐加强。其中，介于长江和黄河流域之间的淮河上游水系离子组成的过渡特征显著。研究区域水系中NO3-主要源于污染物排放，黄河干流污染较西江干流污染重。
3. 西江流域河流溶解态微量金属平均含量Zn>Cr>Cu>As>Al>Pb>Cd，其中Zn平均含量为37.72μg/l，Cd平均含量则仅为0.24μg/l。长江中游溶解态微量金属平均含量Zn>Cr>Pb>As>Cu=Al>Cd。淮河上游溶解态微量金属平均含量Zn>Cr>As>Pb>Al>Cu>Cd。黄河下游溶解态微量金属平均含量Zn>Cr>Cu>As >Al>Pb>Cd。研究区域河流中，西江流域溶解态Cu、Cr的平均含量分别为6.12μg/l和7.61μg/l，高于长江中游、淮河上游及黄河下游。长江中游溶解态Pb和Cd平均含量则高于西江流域、淮河上游及黄河下游。而研究区域中，黄河下游溶解态Al含量最高，达12.7 μg/l，淮河流域则体现出了Zn和Al的高含量特征。
化学风化过程在一定程度上导致了水体与风化壳之间不同化学元素的分异，使河水中溶解态Al和As相对于其它微量金属元素强烈富集，而Pb、Zn、Cu及Cr则相对亏损。河流溶解态As和Al除来源于矿物岩石风化外，也受外源输入—人类活动的影响。
4. 自然条件的区域差异是形成河流离子化学分异的主要因素，但人类活动对其影响逐步加深。工农业污染物输入在一定程度上改变了天然河流的离子化学组成，使河流组分NO3-、SO42-、As、Al等呈现富集趋势。化学元素在河流这一循环过程中间体中的地球化学行为越来越多地受人类活动影响。 |
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