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Application of geographical information system to geoelectrical data for evaluation of the vulnerability of aquifers in parts of Bauchi, Northeastern Nigeria
Environmental Earth Sciences ( IF 2.8 ) Pub Date : 2021-01-05 , DOI: 10.1007/s12665-020-09308-5
Abdullateef Lawal , Moshood N. Tijani , Matteo D’Alessio , Abubakar Sadiq Maigari

The poor quality and inconsistent nature of most surface water supply in arid and semi-arid regions of the world has increased the reliance on groundwater resources. However, the susceptibility of groundwater to anthropogenic pollution in most cities and rural communities in Nigeria has become a major source of concern. In this study, the protective capacity of the aquifers in parts of the Bauchi State, Northeastern, Nigeria, from surface contamination was investigated in light of the geoelectrical characteristics of the overburden materials for sustainable management of the resources. This study applied a geographical information system (GIS) technique to secondary geoelectrical parameters (Dar-Zarrouk) derived from 94 vertical electrical soundings (VES) to delineate aquifer vulnerability zones. Five different thematic maps (topsoil longitudinal unit conductance, total overburden longitudinal unit conductance, total transverse unit resistance, coefficient of anisotropy, and total overburden isopach) were developed. Suitable weights were assigned to the thematic maps based on their relative influence on the protection of groundwater systems in the area. Subsequently, the ranks of the subclasses of the themes were reclassified based on their respective suitability before the thematic maps were integrated using ArcGIS 10.3 software to generate the overall aquifer protective capacity map of the study area. To validate the map, water samples were collected from 40 wells and trace elements (e.g., Ni, Cu, Sb, Cr, and As) were analyzed. The study area was categorized into three aquifer vulnerability zones: moderate (32.4%), weak/fair (54.5%), and low/poor (13.1%). Moderate zones with limited portions of fair/weak zones were the predominant zones within the basement setting. This reflects the occurrence of clayey saprolitic units within the basement terrain (< 100 Ωm) occasioned by weathering of weak ferromagnesian minerals. However, the weak and the poor zones predominate the sedimentary setting with the poor zones concentrated in the southwestern zones of the study underlain by the sedimentary rocks. The poor to weak aquifer protective capacity ratings of the sedimentary settings indicate overburden layers devoid of argillaceous materials and conform to porous and permeable sandy sequences with high transmissivity as revealed by the high transverse unit resistance values (> 15,000 Ωm2). Over 60% of the basement settings are characterized by moderate aquifer protective capacity. On the other hand, the sedimentary zones due to weak and poor protective capacity zones are more vulnerable to pollution. The trace elemental analysis shows the predominance of As, Cu, and Sb in the sedimentary zones as compared to the basement setting which corroborates the aquifer protective capacity map produced.



中文翻译:

地理信息系统在地电数据中的应用,以评估尼日利亚东北部包奇部分地区含水层的脆弱性

在世界干旱和半干旱地区,大多数地表水的质量低劣和性质不一致,增加了对地下水资源的依赖。但是,在尼日利亚的大多数城市和农村社区,地下水对人为污染的敏感性已成为人们关注的主要问题。在这项研究中,根据覆盖层材料的地电特征,对资源的可持续管理进行了调查,研究了尼日利亚东北部包奇州部分地区的含水层对表面污染的保护能力。这项研究将地理信息系统(GIS)技术应用于由94个垂直电测深(VES)得出的次级地电参数(Dar-Zarrouk),以描绘含水层的脆弱性区域。绘制了五种不同的专题图(表土纵向单位电导率,总覆土纵向单位电导率,总横向单位电阻,各向异性系数和总覆土等值线)。根据专题图对当地地下水系统保护的相对影响,为其分配适当的权重。随后,在使用ArcGIS 10.3软件集成主题图以生成研究区域的整体含水层保护能力图之前,根据主题的各自适用性对主题子类的等级进行重新分类。为了验证该图,从40口井中收集了水样,并对痕量元素(例如,Ni,Cu,Sb,Cr和As)进行了分析。研究区域分为三个含水层脆弱性区域:中度(32.4%),弱/中(54.5%),低/低(13.1%)。地下室设置中的主要区域为中等区域,只有有限的软弱区域。这反映了弱铁镁铝矿物风化引起的地下地形(<100Ωm)内粘土质腐殖质单元的发生。然而,软弱和贫困地区占主导地位的沉积环境,贫困地区集中在研究的西南地区,沉积岩的基础上。沉积设置的差至弱含水层保护能力等级表明,上覆层不含泥质物质,并符合高透射率的多孔和可渗透砂质层序,如横向单位电阻值高(> 15,000Ωm)地下室设置中的主要区域为中等区域,只有有限的软弱区域。这反映了弱铁镁铝矿物风化引起的地下地形(<100Ωm)内粘土质腐殖质单元的发生。然而,软弱和贫困地区占主导地位的沉积环境,贫困地区集中在研究的西南地区,沉积岩的基础上。沉积设置的差至弱含水层保护能力等级表明,上覆层不含泥质物质,并符合高透射率的多孔和可渗透砂质层序,如横向单位电阻值高(> 15,000Ωm)地下室设置中的主要区域为中等区域,只有有限的软弱区域。这反映了弱铁镁铝矿物风化引起的地下地形(<100Ωm)内粘土质腐殖质单元的发生。然而,软弱和贫困地区占主导地位的沉积环境,贫困地区集中在研究的西南地区,沉积岩的基础上。沉积设置的差至弱含水层保护能力等级表明,上覆层不含泥质物质,并符合高透射率的多孔和可渗透砂质层序,如横向单位电阻值高(> 15,000Ωm)这反映了弱铁镁铝矿物风化引起的地下地形(<100Ωm)内粘土质腐殖质单元的发生。然而,软弱和贫困地区占主导地位的沉积环境,贫困地区集中在研究的西南地区,沉积岩的基础上。沉积设置的差至弱含水层保护能力等级表明,上覆层不含泥质物质,并符合高透射率的多孔和可渗透砂质层序,如横向单位电阻值高(> 15,000Ωm)这反映了弱铁镁铝矿物风化引起的地下地形(<100Ωm)内粘土质腐殖质单元的发生。然而,软弱和贫困地区占主导地位的沉积环境,贫困地区集中在研究的西南地区,沉积岩的基础上。沉积设置的差至弱含水层保护能力等级表明,上覆层不含泥质物质,并符合高透射率的多孔和可渗透砂质层序,如横向单位电阻值高(> 15,000Ωm)薄弱地区和贫困地区占主导地位,贫困地区主要集中在研究的西南地区,而沉积岩则位于该地区之下。沉积设置的差至弱含水层保护能力等级表明,上覆层不含泥质物质,并符合高透射率的多孔和可渗透砂质层序,如横向单位电阻值高(> 15,000Ωm)薄弱地区和贫困地区占主导地位,贫困地区主要集中在研究的西南地区,而沉积岩则位于该地区之下。沉积设置的差至弱含水层保护能力等级表明,上覆层不含泥质物质,并符合高透射率的多孔和可渗透砂质层序,如横向单位电阻值高(> 15,000Ωm)2)。超过60%的地下室设置以中等的含水层保护能力为特征。另一方面,由于保护能力薄弱的地区造成的沉积区更容易受到污染。痕量元素分析显示,与地下室设置相比,沉积区中As,Cu和Sb占优势,这证实了所产生的含水层保护能力图。

更新日期:2021-01-05
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