云贵高原斜坡地带典型地下水富硫酸盐地区“越层找水”模式及其机理研究

Model and mechanism of "water exploration by cross layer" for high sulfate area in slope region of Yunnan-Guizhou Plateau

地下水是中国西南云贵高原斜坡地带重要的饮用水源,其中黔中镇宁县北部存在大面积地下水中硫酸盐超标地区,导致了当地出现水质性缺水问题。本次研究通过岩相古地理分析、水化学分析、D、18O、34S同位素测试、岩样测试、岩心观察等技术手段,查明了研究区内地下水的补给源主要为大气降水,地下水中硫酸盐(SO_4^(2-))浓度在30～1100 mg/L,平均值为221.78 mg/L,呈现高度富集SO_4^(2-)的特点;在区域相对隔水层以上,不同类型地下水中SO_4^(2-)浓度大体具有机井>上升泉>下降泉>溶潭>地下河出口>基岩裂隙泉>表层岩溶泉的规律;探讨了地表水、地下水中SO_4^(2-)的来源,表层岩溶泉中硫酸根的来源主要为大气降水,高硫酸盐样品中硫酸根的来源主要为石膏溶解。在此基础上,结合钻井资料,掌握了研究区膏岩层分布及含水层结构特征,通过建立"越层找水"模式,采取下层低硫酸盐含水层,获取合格饮用水源,可有效解决当地水质性缺水问题。

Groundwater is an important drinking water source in Southwest China. However, there exists a large area of sulfate exceeding standard in groundwater in the northern part of Zhenning County in Central Guizhou Province, which leads to the problem of water shortage in local area. The following conclusions were obtained by methods of lithofacies palaeogeographic analysis, hydrochemical analysis, D, 18O, 34S isotope test, rock sample test, core observation and other technical methods: The main source of water supply in the study area is meteoric water;the concentration of sulfate (SO4 2-) in groundwater is in the range of 30- 1100 mg/L, with an average value of 221.78 mg/L, showing the characteristics of highly enriched SO4^ 2-;the concentration of SO4^ 2- in different types of groundwater exhibits the law of well > rising spring > falling spring > karst pool > underground river > bedrock fissure spring > epikarst spring;the source of sulfate root in epikarst spring is mainly meteoric water, and the source of sulfate root in high sulfate samples such as J469, J585, ZK3-2 and C010 is mainly dissolved in gypsum. On such a basis and in combination with drilling data, the authors detected the distribution of gypsum rock layer and the characteristics of aquifer structure, and adopted the lower sulfate aquifers to obtain qualified drinking water source by establishing the "cross layer water finding" model, which can effectively solve the problem of water shortage in the study area.