Abstract

The mining site in Itagunmodi, Southwestern Nigeria, was investigated using geophysical and geochemical approaches. This is to ascertain the areas vulnerable to groundwater contamination from mining activities. Airborne Time-Domain Electromagnetic delineated weak zones in the subsurface, facilitating the movement of contaminants into the aquifer. The isolated weak zones were further subjected to ground geophysical survey for detailed investigation. Six (6) Vertical Electrical Sounding and Induced Polarization were located. Fractured layers and thick weathered layers were interpreted as potential groundwater aquifers, having resistivity range of 100–650 ohms/m with average thickness of 5.5 m and the depth of about 5 m to above 50 m within the study area. The metrics utilized to characterize the overburden units’ capacity to protect the aquifer were their layer thickness and resistivity values. Total longitudinal conductance of the overburden layer to the aquifer was generally low, ranging between 0.0102 and 0.0300 mhos, showing that the aquifer protection capacity is inadequate. Due to the low protective capacity of the study area, the aquifer is extremely sensitive to contamination. Six sediment samples from different mine locations collected for further geochemical analysis revealed that the area is highly polluted. The geochemical analysis indicated pollution status and environmental risks associated with the accumulation of Chromium (Cr), Copper (Cu), Lead (Pb), Nickel (Ni), Zinc (Zn), and Manganese (Mn) using contamination indices (statistical parameters). Contaminations from these selected trace elements are as a result of anthropogenic activities of artisanal miners panning for gold in the study area.

中文翻译：

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尼日利亚西南部伊塔贡莫迪地区活跃采矿场的元素痕量富集和污染评估

摘要

使用地球物理和地球化学方法对尼日利亚西南部伊塔贡莫迪的采矿场进行了调查。这是为了确定容易受到采矿活动地下水污染的地区。机载时域电磁描绘了地下的薄弱区域，促进污染物进入含水层。对孤立的薄弱区进一步进行了地面物探详查。定位了六 (6) 个垂直电探测和感应极化。研究区内裂缝层和厚风化层被解释为潜在的地下水含水层，电阻率范围为100-650 ohms/m，平均厚度为5.5 m，深度约为5 m至50 m以上。用于表征覆盖层保护含水层能力的指标是其层厚度和电阻率值。覆盖层对含水层的总纵向电导普遍较低，在0.0102~0.0300 mhos之间，表明含水层保护能力不足。由于研究区防护能力低，含水层对污染极为敏感。从不同矿区采集的六份沉积物样本进行进一步的地球化学分析表明，该地区污染严重。地球化学分析利用污染指数（统计参数）表明与铬（Cr）、铜（Cu）、铅（Pb）、镍（Ni）、锌（Zn）和锰（Mn）积累相关的污染状况和环境风险）。这些选定的微量元素的污染是由于研究区域淘金的手工采矿者的人为活动造成的。