贵中岩溶含水层SO42-运移特征及其硫氧同位素演化机理

In 2015, two important discoveries were made during hydrogeological surveys in Guizhou: 1) the SO42- concentration in the groundwater of Babu Basin was generally higher than 50 mg/L, and peaked at 1959.8 mg/L; 2) the two underground rivers in the basin showed huge seasonal variation in the SO42- concentration between the wet and dry seasons. It is concluded that this is closely related to the groundwater source, migration pathway, water-rock interaction and so on. This study uses hydrochemical analysis, 34S-SO42- and 18O-SO42-, increases the monitoring frequency of SO42- concentrations in underground water on two different time scales (monthly and during the rainfall events), observes the characteristics of 34S-SO42- and 18O-SO42- development, quickly “grasps” the changes in the sources of SO42- in groundwater, and distinguishes between the effects of natural processes and human activities on underground water quality. The terminal element input method is applied to quantify the proportions of SO42- in underground water according to the source, on both monthly and rainfall scales. This paper also examines the migration of SO42- within the two karst aquifers, performs a profile analysis of the mechanisms that influence the development of 34S-SO42- and 18O-SO42- to clarify their occurrences in the groundwater environment. It attempts to set up a diagram modeling the sulfur cycle in the Babu Basin as a framework to help explain sulfur cycles in other small karst watersheds. The results of this study are useful for understanding the development and migration patterns of substances in karst aquifers.

2015年发现八步盆地地下水SO42-浓度:1)很高，多在50mg/L以上，最高达1959.8mg/L；2)盆地内两条地下河水中一个枯水期＞丰水期，另一条则相反。初步推断这与岩溶系统中地下水来源、运移途径、水-岩作用等密切相关。以水化学、34S-SO42-和18O-SO42-为手段，通过观察月、降雨期地下河水SO42-浓度及34S-SO42-与18O-SO42-值演化特征，及时“捕捉”地下水SO42-来源的转变，区分自然过程和人类活动对地下水水质的影响。运用端元输入法，定量求得月和降雨期地下水不同SO42-输入源所占比例。对比分析SO42-在两个岩溶含水层中运移特征，揭示影响34S-SO42-和18O-SO42-演化的机理，以查明地下水赋存环境。尝试在八歩盆地建立硫循环模型图，为更好地了解其他岩溶区小流域硫循环提供一个有用的框架。研究成果将有助于更好解释岩溶含水层中物质的运移演化规律。

岩溶含水层受酸性矿坑水（AMD）的影响日益增加。贵州织金八步地下河流域的地表水、地下水、雨水和AMD水被采集用以分析主要水化学和稳定同位素组成，进而探讨AMD对岩溶含水层的影响及其运移规律。研究发现；（1）流域内AMD水主要受控于硫化物氧化，岩溶管道水受水岩作用和AMD影响，泉水主要受雨水和水岩作用影响；（2）受AMD影响，地下河出口的δ34SSO4出现了偏负的转变，从 3.4‰变为 −13.2‰；（3）受AMD的影响，地下河水因Fe，F-和SO42-超标不可饮用，这种负面生态效应在雨季或受到人类干扰时更加突出；（4）受AMD影响的管道水加速了周围碳酸盐岩的溶解，这种现象在枯水期更加突出，这个过程会向大气释放更多CO2。研究结果表明水化学和同位素（ (δ18OH2O, δ18OSO4和 δ34SSO4)）相结合是研究酸性矿坑水对岩溶含水层影响的重要手段。因此，应当采取合理的措施治理受到尾矿库影响的岩溶含水层。