| 羊卓雍错水体pH偏高的成因 |
| |
| 引用本文： | 保宏运,郭建阳,杨海全,张红梅,马丽.羊卓雍错水体pH偏高的成因[J].环境科学研究,2021,34(3):567-575. |
| |
| 作者姓名： | 保宏运 郭建阳 杨海全 张红梅 马丽 |
| |
| 作者单位： | 1.中国科学院地球化学研究所, 环境地球化学国家重点实验室, 贵州 贵阳 550002 |
| |
| 基金项目： | 国家自然科学基金项目（No.91647205，41877406）；国家自然科学基金-贵州省喀斯特科学研究中心联合项目（No.U1612441） |
| |
| 摘 要： | 羊卓雍错（简称“羊湖”）流域是我国生态环境保护的重点区域，但羊湖水体pH往往超标，令当地管理部门倍感压力.针对羊湖pH偏高的问题，利用地球化学方法，从水化学和流域风化的角度寻找相关线索，以揭示羊湖水体pH偏高的成因.结果表明:①羊湖水体pH在8.5~9.3之间，超标率为49%，同时具有季节性变化特征；而羊湖流域水源（包括地表水、地下水和冰川融水等）pH中间值为8.52，基本代表该流域水源pH的背景值.②羊湖流域水源水化学类型为Ca-HCO3或Ca-SO4，汇入羊湖经历长期蒸发浓缩和复杂地球化学过程后，水化学类型转化为Mg-SO4.③羊湖流域不但存在碳酸盐岩和硅酸盐岩的风化，还有硫化物矿物风化特征.羊湖水体pH超标与羊湖流域水源无关，而是流域风化和其自身长期自然演化的结果.流域风化为羊湖水体提供的大量HCO3-，是羊湖pH在特定条件下自然演化的物质基础.羊湖封闭型水动力学特征使HCO3-滞留并累积在水体中，这为羊湖pH自然演化提供了一个必要条件.在长期蒸发浓缩过程中，水体中一部分HCO3-转化为CO32-，导致水体pH逐渐上升，这是羊湖水体pH偏高的充分条件.简言之，羊湖pH偏高是流域风化、封闭型的水动力学和水体长期蒸发浓缩共同作用的结果.鉴于羊湖水体pH偏高是长期自然演化的结果，建议将pH从羊湖水质管理的考核指标中排除，以免造成不必要的管理成本和压力.
|
| 关 键 词： | 羊卓雍错 pH 水化学 流域风化 |
| 收稿时间： | 2020/2/25 0:00:00 |
| 修稿时间： | 2020/6/4 0:00:00 |
Reasons for High pH Value in Yamzhog Yumco, South Tibet |
| |
| BAO Hongyun,GUO Jianyang,YANG Haiquan,ZHANG Hongmei,MA Li.Reasons for High pH Value in Yamzhog Yumco, South Tibet[J].Research of Environmental Sciences,2021,34(3):567-575. |
| |
| Authors: | BAO Hongyun GUO Jianyang YANG Haiquan ZHANG Hongmei MA Li |
| |
| Affiliation: | 1.State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China2.University of Chinese Academy of Sciences, Beijing 100049, China3.Ecological Environment Bureau of Shannan City, Tibet Autonomous Region, Shannan 856100, China |
| |
| Abstract: | The Yamzhog Yumco watershed is the key region of ecological environment protection in China, but pH value in Yamzhog Yumco is often too high, which puts the local government under tremendous pressure. In order to understand the reasons for the high pH in Yamzhog Yumco, geochemical methods were used to find the clues to its formation mechanism based on the hydrochemistry and weathering in the watershed. The results show that: (1) pH value of Yamzhog Yumco is between 8.5 and 9.3, with the exceeding probability of 49% and seasonal variation, while median value of pH in water sources from the catchment (including surface water, groundwater and glacier melt water, etc) is 8.52, representing the background level of pH in the watershed. (2) Hydrochemical type of water source in the Yamzhog Yumco Basin was Ca-HCO3 or Ca-SO4, but it was changed to Mg-SO4 type after a long period of evaporation and complicated geochemical processes. (3) The weathering in the Yamzhog Yumco Basin is not only characterized by the weathering of carbonate and silicate rocks, but also by the weathering of sulfide minerals. The high pH value in Yamzhog Yumco is the result of watershed weathering and long-term natural evolution of Yamzhog Yumco, and it is not affected by with the water sources. The abundant HCO3- provided by the watershed weathering is the basis for pH evolution in Yamzhog Yumco under specific conditions. Retention and accumulation of HCO3- in Yamzhog Yumco caused by the closed hydrodynamics is the prerequisite for pH evolution in Yamzhog Yumco. The partial conversion of HCO3- to CO32- caused by long-term evaporation leads to an increase in the water pH in Yamzhog Yumco. In short, the high pH of Yamzhog Yumco is the result of the watershed weathering, the closed hydrodynamics and the long-term evaporation of the water body. Since the high pH value of Yamzhog Yumco is the result of long-term natural evolution, it is recommended to remove pH from the water quality management list to avoid unnecessary management costs and pressure. |
| |
| Keywords: | Yamzhog Yumco pH hydrochemistry watershed weathering |
|
| 点击此处可从《环境科学研究》浏览原始摘要信息 |
|
点击此处可从《环境科学研究》下载全文 |
|
