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赤水河流域水化学特征与岩石风化机制

徐森1,2,李思亮3*,钟君3,苏靖3,陈率3   

  1. (1中国科学院地球化学研究所, 贵阳 550081; 2中国科学院大学, 北京 100049;3天津大学表层地球系统科学研究院, 天津 300072)
  • 出版日期:2018-03-10 发布日期:2018-03-10

Hydrochemical characteristics and chemical weathering processes in Chishui River Basin.

XU Sen1,2, LI Si-liang3*, ZHONG Jun3, SU Jing3, CHEN Shuai3   

  1. (1Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; 2 University of Chinese Academy ofSciences, Beijing 100049, China; 3Institute of Surface Earth System Science, Tianjin University, Tianjin 300072, China).
  • Online:2018-03-10 Published:2018-03-10

摘要: 赤水河是长江上游唯一一条干流没有修筑大坝的一级支流,对于探讨河流物质输送与流域岩石风化具有重要的意义。通过对赤水河全流域干流与主要支流进行系统采样,分析了河水的水化学特征及其控制因素,基于化学计量平衡与正演模型方法,计算了大气来源、人为活动输入、硅酸盐岩与碳酸盐岩风化端元对河水溶质的相对贡献,并对流域的岩石风化速率与大气CO2消耗速率进行了估算。结果表明:赤水河流域河水阳离子组成以Ca2+、Mg2+为主,碳酸盐岩风化对河水阳离子的平均贡献率达到77%,大气来源、人为活动输入、硅酸盐岩风化对河水阳离子的平均贡献率分别约为12%、3%和9%;河水阴离子组成以HCO3-、SO42-为主,与长江和乌江等河流相比,河水中SO42-含量较高而HCO3-含量较低。流域硅酸盐岩风化速率与大气CO2消耗速率分别为7 t·km-2·a-1、1.7×105 mol·km-2·a-1,与其他位于西南喀斯特地区的河流接近;仅考虑碳酸风化碳酸盐岩时,流域碳酸盐岩风化速率约为57.6 t·km-2·a-1,大气CO2消耗速率约为4.52×105 mol·km-2·a-1,而在硫酸参与作用下,流域碳酸盐岩风化速率增至为74.6 t·km-2·a-1,大气CO2消耗速率减至为1.74×105 mol·km-2·a-1。硫酸的存在使得赤水河流域碳酸盐岩风化速率估算结果提高了约30%,而相对于其他西南喀斯特地区的河流,由于河水中SO42-含量较高而HCO3-含量较低,使得其风化过程具有较低的大气CO2消耗速率。

关键词: 森林更新, 人工林, 物理作用, 塑料凋落物, 生物量分配

Abstract: Chishui River, the only tributary without the dam in the upper reaches of YangtzeRiver, is of importance for better understanding solute transportation in rivers and the chemical weathering processes. In this study, we investigated the hydrochemical characteristics of the mainstream and major tributaries and its major driving factors in Chishui River Basin. Mass balance and forward model approach were applied to calculate the contribution of different endmembers, the chemical weathering rates, and the atmospheric CO2 consumption rates in the river. Theresults showed that cations of the rivers were dominated by Ca2+ and Mg2+. The contributions of cations derived from atmospheric input, human activities, silicate weathering, and carbonate weathering were 12%, 3%, 9% and 77%, respectively. The anions of the rivers were dominated by HCO3- and SO42-. The Chishui River water had higher SO42- and lower HCO3- concentrations compared with Yangtze River and Wujiang River. The weathering rates and CO2 consumption rates of silicate were estimated to be 7 t·km-2·a-1 and 1.7×105 mol·km-2·a-1, respectively, which were similar to those in other rivers located in karstic areas of southwest China. The weathering rates and CO2 consumption rates of carbonate were estimated to be 57.6 t·km-2·a-1 and 4.52×105 mol·km-2·a-1 after excluding the impacts of sulfuric acid in weathering reactions, respectively. The weathering rates increased to 74.6 t·km-2·a-1 and CO2 consumption ratesdecreased to 1.74×105 mol·km-2·a-1 when considering the sulfuric acid as a carbonate weathering agent. The results suggested that the carbonate weathering rates increased by 30% due to the involvement of sulfuric acid. Due to higher concentration of SO42- and lower concentration of HCO3- in water, CO2 consumption rates were lower in the Chishui River compared to other rivers in karstic areas of southwest China.

Key words: plastic litter, physical effect, forest regeneration, plantation, biomass allocation