长江南通站含沙量及水化学变化与流域的风化过程

1960—2001年间长江河水含沙量递减趋势方程为：S=-4．7273a 582．94。近些年来泥沙含量递减趋势可能会对流域生态环境产生重要影响，应引起社会的关注。长江河水化学组分在1997-2001年的5年间受到季节和年际变化的影响较为有限。河水中HCO3^-与Ca^3 占主导地位，占总离子当量浓度的55％以上。主要受到碳酸盐类溶解的控制。硅酸盐类的风化过程较弱，可能主要是钙镁硅酸盐类的溶解，对流域离子的总体贡献不大。岩盐、石膏和芒硝的水解对河水中的Na^ 、SO4^2-和Cl^-的贡献最大。由此长江流域发生的主要风化过程有：白云石和方解石的溶解、钙镁长石的分解和岩盐、石膏、芒硝等的水解过程等，这与长江流域的岩石特征是基本一致的。粗略的估计．大气CO2对河流中HCO3^-的贡献量占河水中离子总当量浓度的20％左右，其余80％河水溶解质为风化岩石提供。

VARIATIONS OF SOLID CONTENT AND WATER CHEMISTRTY AT NANTONG STATION AND WEATHERING PROCESSES OF THE CHANGJIANG WATERSHED

The data of solid content at two month intervals from1996to2001reveal obvious seasonal variations and the decreasing trend of solid transport,as followed by equation:S=-4.7273a+582.94from1960to2001,which may result in serious environmental problems.Seasonal and annual differences imply that water chemistry of Changjiang River is controlled by the runoff,though the influence is fairly limited.According to the principal composition analysis of river water,water chemistry is mainly controlled by the dissolution of calcite,which is responsible for mostly HCO 3- and Ca 2+ accounting for55%of total ion equivalent concentration.However,silicate weathering plays a minor role in the contribution to the river fluxes,while Na + ?SO 42- and Cl - originate mostly from the halite hydrolyzation,gypsum and Glauber ' s salt dissolution.So the major weathering processes happened in the Changjiang basin include dolomite and calcite dissolution,anorthite weathering and halite,gypsum and Glauber' s salt dissolution.The products by rock weathering are estimated to be80%of the total chemical fluxes while atmospheric CO 2 may contribute20%solute to the river water as the form of HCO 3- in the Changjiang River.