Cao Xing-Xing, Wu Pan, Yang Shi-di, Liu Shan, Liao Jia-Hao
Key Laboratory of Karst Georesources and Environment, Ministry of Education, College of Resource and Environmental Engineering, Guizhou University, Guiyang 550025, China.
Huan Jing Ke Xue. 2021 Apr 8;42(4):1761-1771. doi: 10.13227/j.hjkx.202007163.
The Caohai Lake wetland in Weining County, Guizhou Province, is the largest karst wetland in China, and karst groundwater is an essential source of recharge and material. This study collected groundwater from the Caohai Lake catchment during the wet season, dry season, and flat season, and the main ion components of the groundwater were analyzed. The hydrochemistry characteristics and main ion sources of the groundwater were revealed, and the preliminary estimates of the karst carbon sink flux in the Caohai Lake catchment were calculated based on the solute load method. The results indicated that the water chemistry of the groundwater in the Caohai Lake catchment is primarily the HCO-Ca type, and individual groundwater points in the southeast are the SO-Ca type during the flat season. The dominant ions in the groundwater are Ca, Mg, and HCO. Seasonally, the average concentrations of SO and Mg decreased in the order of flat season>dry season>wet season, while the average concentration of NO decreased in the order of wet season>dry season>flat season, and the seasonal variation of the other ions were not significant. Spatially, the concentrations of Ca and HCO in the groundwater in the northern part of Caohai Lake, of K, Na, and Cl in the southwest, and of Mg, NO, and SO in the southeast were relatively high. Ca, Mg, and HCO in the groundwater were primarily controlled by the dissolution of carbonate rocks, and carbonic acid, sulfuric acid and nitric acid were all involved in the weathering of carbonate rocks in the catchment. Most of the NO in the groundwater was affected mostly by the soil nitrogen and domestic sewage, while NO in the southeast groundwater was primarily affected by agricultural activities. The sources of K, Na, Cl, and SO exhibited no obvious temporal and spatial differences, and the K, Na, and Cl were mainly affected by human activities, while SO was mostly derived from the dissolution of sulfur compounds in the formation. The studied area has a high proportion of allogenic acids (sulfuric acid and nitric acid) participating in the weathering of carbonate rocks, which is the highest in the flat season and the lowest in wet season. After deducting the proportion of allogenic acids participating in the weathering of carbonate rocks, the average inorganic carbon flux in the Caohai Lake catchment is preliminarily estimated to be approximately 181.5 t·a, and the average karst groundwater transport of HCO to Caohai Lake is approximately 1144.1 t·a.
贵州省威宁县的草海湿地是中国最大的喀斯特湿地，喀斯特地下水是其重要的补给源和物质来源。本研究采集了草海流域雨季、旱季和平季的地下水，并分析了地下水的主要离子成分。揭示了地下水的水化学特征和主要离子来源，并基于溶质负荷法对草海流域的喀斯特碳汇通量进行了初步估算。结果表明，草海流域地下水水化学类型主要为HCO-Ca型，平季时东南部个别地下水点为SO-Ca型。地下水中的主要离子为Ca、Mg和HCO。季节上，SO和Mg的平均浓度平季>旱季>雨季依次降低，而NO的平均浓度雨季>旱季>平季依次降低，其他离子的季节变化不显著。空间上，草海北部地下水中Ca和HCO的浓度、西南部K、Na和Cl的浓度以及东南部Mg、NO和SO的浓度相对较高。地下水中的Ca、Mg和HCO主要受碳酸盐岩溶解控制，碳酸、硫酸和硝酸均参与了流域内碳酸盐岩的风化作用。地下水中的NO大部分受土壤氮和生活污水影响，而东南部地下水中的NO主要受农业活动影响。K、Na、Cl和SO的来源在时间和空间上无明显差异，K、Na和Cl主要受人类活动影响，而SO主要来源于地层中硫化合物的溶解。研究区域参与碳酸盐岩风化的外源酸（硫酸和硝酸）比例较高，平季最高，雨季最低。扣除参与碳酸盐岩风化的外源酸比例后，初步估算草海流域平均无机碳通量约为181.5 t·a，HCO从喀斯特地下水向草海的平均输送量约为1144.1 t·a。
