Civil Engineering Department, Central University of Technology Free State, Bloemfontein 9301, South Africa.
Int J Environ Res Public Health. 2020 Apr 10;17(7):2609. doi: 10.3390/ijerph17072609.
Shallow groundwater vulnerability mapping of the southwestern Nigeria sedimentary basin was assessed in this study with the aim of developing a regional-based vulnerability map for the area based on assessing the intrinsic ability of the aquifer overlying beds to filter and degrade migrating pollutant. The mapping includes using the established seven parameter-based DRASTIC vulnerability methodology. Furthermore, the developed vulnerability map was subjected to sensitivity analysis as a validation approach. This approach includes single-parameter sensitivity, map removal sensitivity, and DRASTIC parameter correlation analysis. Of the Dahomey Basin, 21% was classified as high-vulnerability and at risk of pollution, 61% as moderate vulnerability, and 18% as low vulnerability. Low vulnerability areas of the basin are characterised by thick vadose zones, low precipitation, compacted soils, high slopes, and high depth to groundwater. High-vulnerability areas which are prone to pollution are regions closer to the coast with flat slopes and frequent precipitation. Sensitivity of the vulnerability map show the greatest impact with the removal of topography, soil media, and depth to groundwater and least impact with the removal of the vadose zone. Due to the subjectivity of the DRASTIC method, the most important single parameter affecting the rating system of the Dahomey Basin DRASTIC map is the impact of the vadose zone, followed by the net recharge and hydraulic conductivity. The DRASTIC vulnerability map can be useful in planning and siting activities that generate pollutants (e.g., landfill, soak away, automobile workshops, and petrochemical industries) which pollute the environment, groundwater, and eventually impact the environmental health of the Dahomey Basin's inhabitants.
本研究对尼日利亚西南部沉积盆地的浅层地下水脆弱性进行了评估，旨在根据含水层上覆地层过滤和降解迁移污染物的固有能力，为该地区开发基于区域的脆弱性图。该图包括使用已建立的基于七个参数的 DRASTIC 脆弱性方法。此外，还对开发的脆弱性图进行了敏感性分析作为验证方法。该方法包括单参数敏感性、地图删除敏感性和 DRASTIC 参数相关性分析。达荷美盆地的 21%被归类为高脆弱性和易受污染的风险，61%为中等脆弱性，18%为低脆弱性。盆地低脆弱性地区的特征是厚的包气带、低降水、压实土壤、高坡度和高地下水深度。易受污染的高脆弱性地区是靠近海岸的地区，坡度平坦，降水频繁。脆弱性图的敏感性表明，去除地形、土壤介质和地下水深度的影响最大，而去除包气带的影响最小。由于 DRASTIC 方法的主观性，对达荷美盆地 DRASTIC 图评级系统影响最大的单一参数是包气带的影响，其次是净补给和水力传导率。DRASTIC 脆弱性图可用于规划和选址活动，这些活动会产生污染（例如，垃圾填埋场、排水区、汽车修理厂和石化工业），从而污染环境、地下水，并最终影响达荷美盆地居民的环境健康。
