The use of VLF-EM in sedimentary basins has not been fully understood and has not attracted substantial usage in groundwater exploration, specifically in coastal Niger Delta. In the present study, VLF and 2D electrical resistivity imaging (ERI) surveys were combined with hydrogeochemical data to examine groundwater quality. Both interpretations of VLF and 2D ERI uncovered subsurface conductive geologic materials. Eight groundwater and one river water samples as well as static water level were analyzed to complement geophysical data (VLF-EM and ERI). The results suggested that conductive materials detected in the subsurface are unconnected with intrusion of sea water but depicted clay material typical of tidal flat deposits. Furthermore, hydraulic heads estimated from water level and land elevation measurements did suggest that groundwater flows into the Escravos River. Also, the stage of the Escravos River is above water levels in boreholes and hand-dug wells, which is not an indicative of the incursion of salt water into aquifer from the river. The slight level of nitrate loading in groundwater probably suggests contamination emanating from anthropogenic sources such as septic tanks and leachates from diffuse refuse dumps. The study has validated the effectiveness of VLF technique usage in sedimentary basins for the delineation of groundwater quality, but not without important hydrogeochemical data.

中文翻译：

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低频电磁勘测在尼日尔三角洲Oporoza-gbamaratu地区的地下水状况制图中的应用

VLF-EM在沉积盆地中的使用尚不完全清楚，在地下水勘探中，特别是在尼日尔三角洲沿海地区的勘探中，尚未吸引大量使用。在本研究中，VLF和二维电阻率成像（ERI）调查与水文地球化学数据相结合，以检查地下水质量。VLF和2D ERI的两种解释都揭示了地下导电地质材料。分析了8个地下水和1个河水样品以及静态水位，以补充地球物理数据（VLF-EM和ERI）。结果表明，在地下发现的导电材料与海水的入侵无关，但描绘了潮滩沉积物的典型粘土材料。此外，根据水位和土地海拔测量结果估算的水头确实表明地下水流入了埃斯克拉沃斯河。此外，埃斯克拉沃斯河的水位高于钻孔和手挖井中的水位，这并不表示盐水从河中侵入了含水层。地下水中硝酸盐的含量很低，可能表明人为污染源，例如化粪池和扩散垃圾场的渗滤液。这项研究已经证实了在沉积盆地中使用VLF技术来描述地下水质量的有效性，但并非没有重要的水文地球化学数据。这并不表示盐水从河中侵入了含水层。地下水中硝酸盐的含量很低，可能表明人为污染源，例如化粪池和扩散垃圾场的渗滤液。这项研究已经证实了在沉积盆地中使用VLF技术来描述地下水质量的有效性，但并非没有重要的水文地球化学数据。这并不表示盐水从河中侵入了含水层。地下水中硝酸盐的含量很低，可能表明人为污染源，例如化粪池和扩散垃圾场的渗滤液。这项研究已经证实了在沉积盆地中使用VLF技术来描述地下水质量的有效性，但并非没有重要的水文地球化学数据。