信江流域化学风化特征及碳汇效应

Characteristics of Chemical Weathering and Carbon Sink Effect in Xinjiang River Basin

选取鄱阳湖流域信江作为研究对象,分析其主要离子组成;采用Gibbs图解法判断溶质来源,利用放射性核素铀作为端元识别主要风化类型,并利用质量平衡方法估算河流内不同端元对化学风化的贡献值和风化速率,计算了流域内CO2消耗量及其消耗速率。结果表明:信江流域水化学类型为Ca-HCO3,大气降水为河流重要补给来源,在中、下游有少量地下水补给。河水化学组分主要受岩石风化控制,碳酸岩主导了岩石风化过程。各个端元值对化学风化的贡献率为碳酸岩(50.8%)>硅酸盐(32.4%)>蒸发岩(12.8%)>大气降水(4%);人类通过矿山开采活动影响SO4^2-,从而对流域化学风化产生贡献,贡献率为13.2%。信江流域内碳酸岩风化速率为25.2 t/(km^2·a),硅酸盐风化速率为17.2 t/(km^2·a),总风化速率为42.4 t/(km^2·a)。信江流域内岩石风化过程大气CO2的消耗量为7.9×109 mol/a,占鄱阳湖流域CO2的消耗量(74.39×109 mol/a)的10.6%;CO2的消耗速率为448.9 mol/(a·km^2)。

Xinjiang River in Poyang Lake Basin was selected as the research object to analyze the main ion composition.Gibbs graphic method was used to determine the source of solute and the radionuclide uranium was used as the terminal element to identify the main weathering types.The contribution rates of different elements to chemical weathering in rivers is estimated by mass balance method.The consumption of CO2 and its consumption rate and weathering rate of different rocks are calculated.The results show that the hydrochemical type of the river is Ca-HCO3,precipitation is an important source of recharge in the river basin,and there is a small amount of groundwater recharge in the middle and lower reaches.The chemical components of river water are mainly controlled by rock weathering,and carbonate rocks dominate the chemical weathering process.The contribution rate order of each end element to chemical weathering is:carbonate(50.8%)>silicate(32.4%)>evaporative rock(12.8%)>atmospheric precipitation(4%);human activities have an effect on the concentration of SO4^2-,which contributing to the chemical weathering of the basin with a contribution rate of 13.2%.The weathering rate of carbonate rocks in Xinjiang river basin is 25.2 t/(km^2·a),silicate weathering rate is 17.2 t/(km^2·a),total weathering rate is 42.4 t/(km^2·a).The consumption of CO2 during rock weathering in Xinjiang river basin is 7.9×109 mol/a,accounting for 10.6%of the consumption of CO2(74.39×109 mol/a)in Poyang lake basin;the consumption rate of CO2 is 448.9 mol/(a·km^2).