韩江流域河水地球化学特征与硅酸盐岩风化——风化过程硫酸作用

流域岩石化学风化是全球碳循环的重要环节之一,硅酸盐岩风化过程消耗大气CO_2,是在地质时间尺度上调节大气CO_2浓度的重要机制。本工作在对我国东南花岗岩地区流经典型的硅酸盐岩地质背景河流——韩江流域河流水化学组成研究的基础上,分析和定量计算了河流水体主要物质来源,并对硫酸参与岩石风化和碳循环过程的作用进行了分析,进而对韩江流域岩石风化速率及其大气CO_2消耗通量进行了估算。结果表明,韩江流域河流主离子组成主要来源于硅酸盐岩和碳酸盐岩风化,并计算得出约41%的硫酸根离子来自于大气降水;流域碳酸盐岩的风化速率为21.7 t/(km~2·a),硅酸盐岩为18.9 t/(km~2·a)。硫酸参与岩石风化提供的离子贡献占流域岩石风化提供总离子量的65.9%;流域风化带来的CO_2消耗速率被高估了约61%。

River Water Geochemistry of Hanjiang River, Implications for Silicate Weathering and Sulfuric Acid Participation

Chemical weathering is an important process in global carbon cycle, and the weathering of silicate rocks is a significant mechanism for regulation of atmospheric CO₂ concentrations on geological time scale. In this study, we analyzed ion compositions of water in the Hanjiang River Basin, which are lithologically dominated by silicate rocks and located in the Southeast of China. We estimated the rock weathering rate and CO₂ consumption flux in the Hanjiang River Basin. Besides, sulfuric acid participating rocks weathering and carbon cycle processes were identified. Results show that water chemistry in the Hanjiang River Basin is mainly controlled by chemical weathering of silicate rocks and carbonate rocks. The weathering rate of carbonate rocks is 21.7 t/(km²·a) while the rate of silicate rocks is 18.9 t/(km²·a).Calculations of end-member contribution indicate that 41% of the SO₄^2- originated from precipitation. The presence of sulfuric acid increased the cationic load account for 65.9% of the total cationic load origin, and overestimated CO₂ consumption rate by 61%.