寒温带流域硅酸盐岩的风化特征--以嫩江为例

Characteristics of silicate rock weathering in cold temperate zone: A case study of Nenjiang River, China

测定了嫩江水系河水主要离子组成(Ca2+、Mg2+、Na+、K+、HCO3-、SO42-、Cl-),分析了不同类型岩石风化、大气降水、人为输入对河水溶解质的相对贡献,并对整个流域以及各子流域的岩石风化速率和CO2消耗速率进行了估算。结果表明,嫩江水系河水呈弱碱性,pH平均值为7.5;阳离子以Ca2+为主,约占阳离子总量的50%;阴离子以HCO3-为主,约占阴离子总量的85%。河水中的阳离子主要来源于硅酸盐岩风化(约38%)和碳酸盐岩风化(约32%),其余来源于蒸发岩溶解(约25%)和人类活动(约5%)以及大气降水输入(<1%)。嫩江流域硅酸盐岩风化速率约为1.37t·km-2·a-1(TDS硅酸盐岩),硅酸盐岩风化对大气CO2的消耗速率约为40.1×103mol·km-2·a-1。

We determined the concentrations of major ions （ Ca^2＋, Mg^2＋Na^＋, K^＋, and HCO3-, SO42-, and C1- ） in the waters of Nenjiang River system, China, analyzed the relative contribu- tions of chemical weathering of different kinds of rocks, atmospheric input, and human input to the total dissolved solutes, and estimated the chemical weathering rates of different kinds of rocks and associated atmospheric CO2 consumption rates in the whole basin and each sub-basin. The water of the Nenjiang River system was weakly alkaline, with an average pH of 7.5, calcium was the dominant cation, accounting for 50% of the total cations, and HCO3- was the most abundant anion, accounting for 85% of the total anions. The dissolved cations in the waters were mainly originated from silicate weathering （ -38% ） and carbonate weathering （ -32% ）, and from the dissolution of evaporates （ - 25% ）, human activities （ - 5% ）, and atmospheric precipitation input （〈1%）. The average chemical weathering rate of silicate rock in the basin was approxi- mately l. 37 t ·km-2 · a-l（ total dissolved solids of silicate rock）, and the associated atmospher- ic CO2 consumption rate was about 40. lxl03 mol · km-2 · a-1