Sako Aboubakar, Ouangaré Cheik Abba Cissé
UFR Sciences Appliquées et Technologie, Université de Dédougou, BP 139, Dédougou, Burkina Faso.
Laboratoire Géosciences et Environnement (LaGE), Département des Sciences de la Terre, Université Joseph Ki-Zerbo, Ouagadougou, Burkina Faso.
Environ Monit Assess. 2023 Mar 28;195(4):519. doi: 10.1007/s10661-023-11127-7.
Hydrogeochemical processes that govern selected inorganic substances distribution in a semi-confined aquifer were characterized using traditional hydrogeochemical approaches and natural background levels (NBLs). Saturation indices and bivariate plots were used to investigate the effects of water-rock interactions on natural evolution of the groundwater chemistry, whereas Q-mode hierarchical cluster analysis and one-way analysis of variance classified the groundwater samples into three distinct groups. To highlight the groundwater status, NBLs and threshold values (TVs) of the substances were calculated using pre-selection method. Piper's diagram showed that the Ca-Mg-HCO water type was the only hydrochemical facies of the groundwaters. Although all samples, except a borewell with a high NO concentration, had major ion and transition metal concentrations within the World Health Organization's recommended guideline values for drinking water, Cl, NO and PO exhibited scattered distribution patterns, reflecting their nonpoint anthropogenic sources in the groundwater system. The bivariate and saturation indices revealed that silicate weathering and possible gypsum and anhydrite dissolution contributed to the groundwater chemistry. In contrast, NH, Fe and Mn abundance appeared to be influenced by redox conditions. Strong positive spatial correlations between pH, Fe, Mn and Zn suggested that mobility of these metals was controlled by pH. The relative high F concentrations in lowland areas may imply the impact of evaporation on this ion's abundance. Contrary to TVs of HCO, those of Cl, NO, SO, F and NH were below the guideline values, confirming the influence of chemical weathering on the groundwater chemistry. Based on the present findings, further studies that take into account more inorganic substances are required for NBLs and TVs determination in the area, thereby setting up a robust sustainable management plan for the regional groundwater resources.
利用传统水文地球化学方法和自然背景值（NBLs）对控制半承压含水层中特定无机物质分布的水文地球化学过程进行了表征。饱和指数和双变量图用于研究水岩相互作用对地下水化学自然演化的影响，而Q型层次聚类分析和单因素方差分析将地下水样本分为三个不同的组。为突出地下水状况，采用预选法计算了这些物质的NBLs和阈值（TVs）。派珀图表明，Ca-Mg-HCO水型是地下水唯一的水化学相。尽管除一口NO浓度较高的井外，所有样本的主要离子和过渡金属浓度均在世界卫生组织饮用水推荐指导值范围内，但Cl、NO和PO呈现出分散的分布模式，反映了它们在地下水系统中的非点源人为来源。双变量和饱和指数表明，硅酸盐风化以及可能的石膏和硬石膏溶解对地下水化学有贡献。相比之下，NH、Fe和Mn的丰度似乎受氧化还原条件影响。pH、Fe、Mn和Zn之间存在很强的正空间相关性，表明这些金属的迁移受pH控制。低地地区相对较高的F浓度可能意味着蒸发对该离子丰度的影响。与HCO的TVs相反，Cl、NO、SO、F和NH的TVs低于指导值，证实了化学风化对地下水化学的影响。基于目前的研究结果，该地区需要进一步开展考虑更多无机物质的研究，以确定NBLs和TVs，从而为区域地下水资源制定稳健的可持续管理计划。
