马莲河流域河水化学特征和化学风化过程分析

Hydrochemistry and Chemical Weathering Processes of Malian River Basin

采用Gibbs图解和端元分析方法研究了马莲河水化学特征、离子来源和化学风化作用,利用质量平衡正演模型评价了各风化作用对水化学组分的贡献率。结果表明,马莲河水为高TDS咸水,阳离子以Na^＋、Mg^2＋为主,阴离子以Cl^-、SO4^2-为主;沿河水流向TDS降低,水化学类型由Cl-Na型演变为HCO3·SO4-Na·Mg型;河水化学组分的主要形成作用为化学风化,蒸发盐主导了流域风化过程,对离子组分平均贡献率高达76.5%,硅酸盐和碳酸盐风化较弱;化学风化具空间变异,从上游到下游,硫酸盐和碳酸盐贡献率增加,岩盐贡献率降低。岩性是控制流域化学风化作用的首要因素,降雨量和径流量可能也有一定影响。

In this study,Gibbs plots and end-member analysis methods were used to identify hydrochemistry,solute sources and chemical weathering processes of Malian river. A forward model of mass budget was established to evaluate the contribution to river water mineralization for halite,sulfate,silicate and carbonate weathering. Results show that river water in this area was brackish with high total dissolved solids and dominated by Na^＋,Mg^2＋,Cl^- and SO4^2-. Along flow path,the total dissolved solids of river water decrease and hydrochemical type transfers from Cl-Na upstream to HCO3·SO4-Na·Mg downstream. Water chemistry was mainly controlled by weathering processes,in which evaporite plays a dominant role with average contribution of 76. 5%,while silicate and carbonate weathering have contributions of 10. 4% and 13. 1%,respectively. From upstream to downstream,chemical weathering processes vary spatially and the contribution decreases for halite,while increases for sulfate and carbonate. Lithology condition is the primary factor affecting chemical weathering processes and rainfall and water discharge also highlight significant impacts on water chemistry.