School of Physical Sciences, Department of Chemistry, University of Cape Coast, Cape Coast, Ghana.
CSIR-Water Research Institute, P.O. Box AH 38, Achimota, Ghana.
Environ Monit Assess. 2022 Dec 29;195(1):246. doi: 10.1007/s10661-022-10760-y.
The Oti Basin is located at northeastern part of Ghana. Two major geological formations of Voltaian sedimentary supergroup exist: Kwahu-Morago and Oti-Pendjari groups. A total of 133 groundwater samples and 7 surface water samples were collected for two major seasons, viz. dry season (February, 2020) and wet season (November, 2020), and analysed for cations and anions. This is to determine the sources of ions, including pollutants and the reactions that promote them for sustainable groundwater management. Results of major ions revealed groundwater is potable base on the WHO permissible limits. Wet season nitrate and sulphate were higher than that of dry season, suggesting anthropogenic influence. Pearson's correlation shows major contributors of total dissolved solids were Mg, Na and HCO with a correlation (r = 0.439, 0.874 and 0. 945) respectively. In the wet season, major contributors were TH, Mg, Na, SO and HCO with correlation (r = 0.548, 0.537, 0.856, 0.530 and 0.936) respectively. Gibbs plot suggests chemical weathering and precipitation to be the main contributors to the water chemistry. The dominant hydrochemical facies within the basin for both seasons was Na-K-HCO water type. The plot of Ca + Mg vs. HCO3 + SO4 suggests both silicate weathering and ion exchange processes are taking place within the basin. Mineral stability diagrams signify kaolinite as the most stable mineral phase in the groundwater. Chloro-alkaline indices were negative for both seasons leading to base-exchanged softened water production. Consequently, majority of ions evolved from natural geochemical processes whilst nitrate and sulphate presence might be due to anthropogenic sources.
奥蒂盆地位于加纳东北部。存在两个主要的沃尔特沉积超群地质构造：夸胡-莫拉戈组和奥蒂-彭杰里组。在两个主要季节（2020 年 2 月的旱季和 2020 年 11 月的雨季）共采集了 133 个地下水样本和 7 个地表水样本，并对阳离子和阴离子进行了分析。这是为了确定离子的来源，包括污染物和促进它们的反应，以实现地下水的可持续管理。主要离子的结果表明，根据世界卫生组织允许的限度，地下水是可饮用的。雨季的硝酸盐和硫酸盐含量高于旱季，表明存在人为影响。皮尔逊相关性分析显示，总溶解固体的主要贡献者是 Mg、Na 和 HCO，相关性分别为 0.439、0.874 和 0.945。在雨季，主要贡献者是 TH、Mg、Na、SO 和 HCO，相关性分别为 0.548、0.537、0.856、0.530 和 0.936。吉布斯图表明，化学风化和降水是水化学的主要贡献者。两个季节盆地内主要的水文地球化学相是 Na-K-HCO 水型。Ca2+ -Mg2+ 与 HCO3- + SO42-的关系图表明，硅酸盐风化和离子交换过程都在盆地内发生。矿物稳定性图表明，高岭石是地下水中最稳定的矿物相。氯-堿度指数在两个季节均为负值，导致基交换软化水的产生。因此，大多数离子是由自然地球化学过程演化而来的，而硝酸盐和硫酸盐的存在可能是人为来源造成的。
