黔中茶店桥地下河流域不同水体硫酸盐浓度特征及来源识别

Sulfate Concentrations and Source Identification in Different Water Bodies of the Chadianqiao Underground River Basin in Central Guizhou

茶店桥地下河位于西南岩溶区,流域内"三水"转换迅速,地下水是当地的重要饮用水源。本文对流域内雨水、地表水、地下水中的SO_4^(2-)浓度进行了测试,利用氘(δD_(H_2O))、氧(δ^(18) O_(H_2O))同位素示踪地表水、地下水补给来源,用硫酸盐硫(δ^(34)S_(SO4))、氧(δ^(18) O_(SO4))同位素探讨了地表水、地下水中SO_4^(2-)的来源,并计算了地下河出口河水中不同SO_4^(2-)来源的贡献比例。结果表明:1不同水体中SO_4^(2-)浓度大小顺序为地表水>地下水>雨水,与邻近区域相比,茶店桥地下河流域雨水、地表水、地下水呈现富集SO_4^(2-)的特征。2地表水、地下水的主要补给来源为大气降水,硫酸不仅和HCO_3^-共同参与了流域内碳酸盐岩的溶解,也参与了雨水中含钙镁颗粒物的溶解。3地表水δ^(34)S_(SO4)、δ^(18) O_(SO4)值分别介于-12.98‰^-10.19‰和-0.54‰^+9.13‰之间,地下水δ^(34)S_(SO4)、δ^(18) O_(SO4)值分别介于-14.32‰^+16.58‰和+2.81‰^+14.35‰之间,SW02的SO_4^(2-)主要来源于大气降水,SW01、SW03、GW02、GW03、GW06主要来源于煤层,GW05主要来源于石膏,GW01、GW04为混合输入源。4地下河出口河水中大气降水带来的SO_4^(2-)贡献比例为13%,煤层硫化物氧化的贡献比例为40%,石膏溶解的贡献比例为47%。

The Chadianqiao underground river is located in karst areas in southwestern China, where the movement of the water, including rainwater, surface water, and ground water is extremely rapid. The groundwater in the area is an important source of local drinking water. This study measured the sulfate （SO4^2-） concentration of rainwater, surface water, and groundwater in the drainage basin. Deuterium （δDH2O） and oxygen （δ^18 OH2O） isotopes were used to track the source of the surface water and groundwater. Sulfur （δ^34 SSO4） and oxygen （δ^18 OSO4）isotopes in the SO4^2- were employed to identify the source of SO42 in the surface water and groundwater, additionally, to quantify the proportion contributed by the different SO4^2- sources at the underground river outlet. The results demonstrated that 1） the SO4^2- concentrations in the different water bodies were （in descending order） surface water,groundwater） rainwater. The SO4^2- was more enriched in the Chadianqiao underground river basin than in the adjacent river basins. 2） The major recharge source of surface water and groundwater was precipitation. The SO4^2- was active in the dissolution of carbonate rocks in the river basin together with HCO3^-, as well as in the dissolution of the calcium/magnesium particles in the rainwater. 3） The δ^34 SSO4 and δ^18 OSO4 values of the surface water ranged between -12.98‰and -10.19‰, and -0.5‰ and ＋ 9.13‰, respectively. The δ^34 SSO4 and δ^18 OSO4 values of the groundwater ranged between -14.32‰ and ＋16.58‰, and ＋2.81‰ and ＋14.35‰, respectively. The SO4^2- in SW02 mainly derived from precipitation, whereas that in SW01, SW03, GW02, GW03, and GW06 mainly derived from coal. The SO4^2- in GW05 derived from gypsum, whereas that in GW01 and GW04 derived from mixed sources. 4） At the underground river outlet, 13‰ of the SO4^2- derived from precipitation, 40% from sulphide oxidation in coal seams, and 47% from the dissolution of gypsum.