An Integrated Magnetotelluric and Gama Exploration of Groundwater in Fractured Granite for small-scale freshwater supply: a case study from the Boshan Region, Shandong Province, China
An Integrated Magnetotelluric and Gama Exploration of Groundwater in Fractured Granite for small-scale freshwater supply: a case study from the Boshan Region, Shandong Province, China
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用于小型淡水供应的裂隙花岗岩地下水综合大地电磁和伽马勘探：以中国山东省博山地区为例
DOI：
10.1007/s12665-017-6486-z
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发表时间：
2017
影响因子：
2.8
通讯作者：
Lv Lianghua
中科院分区：
文献类型：
--
作者：
Li Jie;Pang Zhonghe;Kong Yanlong;Lin Fangli;Wang Yalu;Wang Guangjie;Lv Lianghua
在坚硬岩石中勘探和利用地下水是一个困难而又重要的问题，特别是在当地地表水受到污染的情况下。本文采用地球物理与核相结合的方法，对山东博山花岗岩地层进行了含水圈定。构造分析表明，裂缝沿NW-SE方向伸展，与河谷方向一致。沿河谷进行的可控源音频大地电磁测量显示了几个不同的低阻异常或潜在的含水裂缝带。它们位于距离河谷地表400米的深度范围内。在河谷附近发现的高伽马辐射测量进一步证实了深水含水带的位置。推断该河流附近的北西-东南走向断层为异常含水带。在含水区钻了两口管井，单井出水量大于360立方米/天。对井水进行了水化学和稳定同位素分析。浅层地下水样品显示出与河水相似的水化学和同位素特征，表明两者之间存在联系。含水断裂带的深部地下水与浅层地下水没有水力连接，保证了花岗岩深部地下水的安全，不受浅层地下水或河水污染的影响。综合地球物理和伽马勘探方法帮助确定了两个不相连的地下水系统，如果浅层地下水或地表水受到污染，则为该地区提供了替代淡水来源。
Exploration and use of groundwater in hard rocks is a difficult but yet a significant issue, especially when the local surface water source is polluted. In this study, integrated geophysical and nuclear methods are used to delineate groundwater-bearing zones in a granite terrain in the Boshan region, Shandong Province, China. Structural analysis showed that fractures extend in a NW–SE direction, which is the same as the direction of river valley. A controlled source audio-frequency magnetotelluric survey conducted along the river valley indicated several different low resistivity anomalies or potential water-bearing fracture zones. They are seated at depth ranges down to 400 m from the surface along the river valley. The locations of deep water-bearing zones were further confirmed by higher gamma radiation measurements found near the river valley. A fault with a NW–SE strike near the river was deduced as an anomalous water-bearing zone. Two tube wells were drilled targeting at the water-bearing zone that has achieved single-well water yield greater than 360 m3/day. The well water was sampled for water chemistry and stable isotope analyses. Shallow groundwater samples show similar water chemistry and isotopic feature to river water, indicating connection between the two. Deep groundwater from the water-bearing fracture zones is not hydraulically connected with shallow groundwater, ensuring safety of the deep groundwater in the granite from being affected by the polluted shallow groundwater or river water. Integrated geophysical and gamma exploration methods helped to identify two disconnected groundwater systems, offering an alternative freshwater source for the region if shallow groundwater or surface water is polluted.