Sulfate (SO42-) is an essential anion in drinking water and a vital macronutrient for plant growth. However, elevated sulfate levels can impact ecosystem or human health and could be an important indicator of acid rock drainage or pollution. Therefore, monitoring SO42- sources and transport is important for water quality assessments. This study focused on exploring the sources and transformations of SO42- as well as estimating the proportional contribution of the potential SO42- pollutant sources to groundwater and surface water in a tropical river basin, the Densu River Basin. The study used major ions combined with stable sulfur and oxygen isotope compositions and a Bayesian isotope mixing model, MixSIAR. The major ion characteristics indicate that SO42- concentrations remain stable throughout the rainy and dry seasons but originate from diverse sources. The multiisotope model (delta S-34(SO4), (SOSO4)-O-18) identified four potential SO42- sources: detergent, precipitation, sewage, and sulfate fertilizer. However, the delta S-34(SO) and (SOSO4)-O-18 values of the fertilizer source signatures overlapped with those of precipitation and sewage. Nevertheless, the contributions from each source were disentangled using the MixSIAR model, which revealed sewage as the most dominant SO42- pollutant in the Densu Basin, accounting for similar to 47 % of sulfate in groundwater and similar to 56 % of sulfate in surface water. Sulfate fertilizer (similar to 33 %) was the second most important source after sewage for groundwater, while detergent (similar to 23 %) was the second most important source for surface water. The redox processes of bacterial sulfate reduction and sulfide oxidation were determined to have a minimal impact on the sulfur isotope fractionation within the basin. This study highlights the benefits of combining major ions, sulfur isotopes and the MixSIAR model for identifying sources of sulfate. This approach accounts for uncertainties in source contributions which allows for more robust and reliable apportionment of sulfate sources. The study emphasizes the need for effective waste management and pollution control measures to protect water quality and provides vital guidelines on how to partition sulfate sources on a large catchment scale and evidence for making pollution management decisions on water resources.

In the Tano River Basin, groundwater serves as a crucial resource; however, its quantity and quality with regard to trace elements and microbiological loadings remain poorly understood due to the lack of groundwater logs and limited water research. This study presents a comprehensive analysis of the Tano River Basin, focusing on three key objectives. First, it investigated the aquifer hydraulic parameters and the results showed significant spatial variations in borehole depths, yields, transmissivity, hydraulic conductivity, and specific capacity. Deeper boreholes were concentrated in the northeastern and southeastern zones, while geological formations, particularly the Apollonian Formation, exhibit a strong influence on borehole yields. The study identified areas with high transmissivity and hydraulic conductivity in the southern and eastern regions, suggesting good groundwater availability and suitability for sustainable water supply. Secondly, the research investigated the groundwater quality and observed that the majority of borehole samples fall within WHO (Guidelines for Drinking-water Quality, Environmental Health Criteria, Geneva, 2011, 2017. http://www.who.int ) limit. However, some samples have pH levels below the standards, although the groundwater generally qualifies as freshwater. The study further explores hydrochemical facies and health risk assessment, highlighting the dominance of Ca–HCO 3 water type. Trace element analysis reveals minimal health risks from most elements, with chromium (Cr) as the primary contributor to chronic health risk. Overall, this study has provided a key insights into the Tano River Basin’s hydrogeology and associated health risks. The outcome of this research has contributed to the broader understanding of hydrogeological dynamics and the importance of managing groundwater resources sustainably in complex geological environments.

Fertilizers increase agricultural productivity and farmers' income. However, intensive agriculture frequently overuses fertilizers, which in turn can contaminate surface and groundwater. In this study, hydrochemical and multi-isotope (δ15NNO3, δ18ONO3 and δ18OH2O) data have been combined to identify nitrate pollution sources in Ghana's Densu River Basin, trace the Nitrogen (N) biogeochemical processes in the basin and apportion the contribution of each pollution source. Surface water NO3- ranged from 0.3 to 10.6 mg/L (as N), while groundwater NO3- ranged from 0.9 to 34 mg/L. Hierarchical cluster analysis classified the water samples into three spatial categories: upstream, midstream, and downstream, reflecting river and land use patterns. The multi-isotope model considered five primary NO3- sources: atmospheric deposition, manure/sewage, NH4+ in fertilizers, other NO3- based fertilizers and soil N. Nitrification was identified as the major biogeochemical process upstream, whereas mixing of sources and denitrification dominate the midstream to downstream sections of the basin. Nitrate source apportioning using a MixSIAR model reveal that N fertilizers (40 %) and soil N (34 %) contribute the most to nitrate pollution upstream of the river. From the midstream to downstream sections, manure/sewage (43 %) become the dominant nitrate source, reflecting the transition from agriculture to peri-urban and urban land use. This study has shown that soil erosion and runoff contribute to nitrate pollution in the Densu River, at levels comparable to N fertilizers, and groundwater across the basin is impacted mainly by manure/sewage. The multi-isotope analyses allowed the partitioning of N sources in other ways not possible using only classical hydrochemical methods.

Investigating sources and evolution of groundwater in the Black Volta River basin is vital for understanding aquifer chemical configuration. Though resettlement has made groundwater in the region an important water supply source, its hydrochemical origin is poorly understood. Therefore, hydrochemistry was coupled with stable isotope (delta H-2 and delta O-18) techniques to improve knowledge for effective groundwater resource management. For this purpose, 23 boreholes were sampled in the Black Volta River basin of Ghana. Major ion dominance is in the order: Na+ > Ca2(+) > Mg2(+) >K+ and HCO3 > Cl > SO42 -> NO3- respectively. Hydrochemical facies indicates the presence of soluble silicate minerals within aquifer. Hierarchical cluster analysis showed higher ionic concentration within aquifers which decreases towards discharge areas. This is attributed to longer residence time at lower elevations leading to interaction of water with silicate and accessory minerals. Oxygen-18 spatial plot shows recharge occurs along subsurface fractured zones which is confirmed by the water table contour of the study area. Natural geochemical processes, anthropogenic influences and the dissolution of silicate/albite components were extracted using Principal component analysis/factor analysis. These two components which explains the hydrochemistry constituted 79.5% of the total variance in the hydrochemical data and have eigen values > 1. Isotopic composition of groundwater indicates is of meteoric origin and the aquifers were recharged by precipitation. The outcome of this study provides theoretical support for the monitoring and management of groundwater, and its implication on the migration of people in arid/semi-arid regions.

Stable Isotope (& delta;2H and & delta;18O) technique is employed to investigate the Dam water-groundwater interaction on the Bui hydropower project in Ghana, to ascertain; if surface water from the dam recharges the groundwater or if there is balance flow relationship between the two systems. The hydrochemical results showed that the pH of the groundwater (5.51-7.18) was slightly acidic to basic, predominantly due to lithology. The pH of the surface water (6.13-6.98) suggests decomposition of submerged organic matter at the impoundment of the dam. The hydrochemical facies showed signatures that result from groundwater interaction with soluble aquifer materials (feldspars, micas, and quartz). Stable isotope in the study area showed surface water is more enriched (& delta;18O = -2.46%0; & delta;2H -21.48%0) than rainwater (& delta;18O = -3.36%0; & delta;2H = - 17.83%0), which is slightly enriched than groundwater (& delta;18O = -3.58%0; & delta;2H = - 17.48%0). The stable isotope (& delta;2H-& delta;18O) biplot indicates that no interaction occurred between the groundwater and the Black Volta River; the groundwater in the catchment is of meteoric origin. D-excess confirms mineralization due to water-rock interaction while the biplot of Cl- versus & delta;18O delineated three (3) groups of water i.e., water being bridged by rocks; groundwater recharged by rainfall with little or no evaporation and evaporated groundwater. Residence time influences groundwater's ionic configuration which imparts aesthetic characteristics over time. The study confirms the feasibility of complimenting geochemistry with the isotope technique to investigate flow relationships between dam water and groundwater systems.

Soil serves as a vast matrix for heavy metal accumulation and subsequent redistribution to critical aspects of the environment such as groundwater. Soil pollution study is essential for sustainable human health and ecosystem protection. This study provides vital insight into the fate, accumulation, interactions, and health risk posed by heavy metals in soil and groundwater by employing geochemical accumulation index (Igeo), risk assessment models and multivariate data analysis techniques such as principal component analysis (PCA), preference ranking organisation method for enrichment evaluation (PROMETHEE) and geometrical analysis for interactive aid (GAIA). The median Igeo estimates show moderate to strong Pb accumulation levels whilst all the other metals indicate uncontaminated to moderate levels. The PCA output point to anthropogenic origin of Pb and Cd in the Tano Basin and surrounding communities. PROMETHEE-GAIA results indicate that Pb, Cd, Zn and Fe accumulated in the soil matrix may potentially leach into the groundwater resources. The carcinogenic lifetime risks posed by Pb, Cd, and Ni metals to adults are within the tolerable acceptable risk and thus do not present an immediate danger in the study area. Due to the significant toxicity, bioaccumulation and biomagnification properties of Pb and Cd in the environment, areas associated with significant anthropogenic activities require regular monitoring and evaluation in order to ensure that these metals are consistently below the regulatory limits. This study has further elucidated the subject of heavy metal pollution and is therefore expected to enhance sustainable protection of the environment and human health.

This work is to establish the hydrochemistry and origin of groundwater in some parts of the Gushegu district of the Northern Region of Ghana. Hydrochemical data from 19 groundwater and 7 rock samples have been used to evaluate water quality, water types, and sources of various ions as well as origin of the groundwater. The study results show that the quality of groundwater from the area is generally not good due to their fluoride (F − ), bicarbonate (HCO 3 − ) and electrical conductivity (EC) concentrations. The F − contents of the groundwater have values as high as 1.97 mg/L, with 53 % of the groundwater having concentrations of F − exceeding the WHO recommended allowable limits. These high F − values have the potential of causing serious health problems such as kidney failure, dental and skeletal fluorosis, reproductive problem and reduction in intelligent quotient of consumers. A plot of Gibbs diagram reveals that rock weathering and precipitation are the major hydrogeochemical processes regulating the water chemistry of the study area. Petrographic thin-section analyses of rock samples identify minerals present to be muscovite, plagioclase feldspars, quartz, sericite and iron oxide. Stable isotope ( 18 O and 2 H) composition of the waters reveals that most of the groundwater is likely to be recharged from local precipitation, indicating their meteoric origin. Some samples, however, showed considerable evaporation.

This paper assesses groundwater in the Ga West Municipal Area of Ghana using hydrogeochemistry and isotope approaches. High salinity groundwaters are obtained in the municipality which poses problems for current and future domestic water supply exploitation. The increase in salinity is related to the dissolution of minerals in the host rocks and the evaporative concentration of solutes. The dominant groundwater composition in both shallow and deep wells sampled is Na–Cl. The concentration of the Na–Cl was observed to increase substantially with well depths. The mixing of freshwater of the shallow hand dug wells with that of saline water of the deep boreholes was noted in the shift from Ca–HCO 3 facies to Ca–Cl facies. Schoeller diagram showed that groundwater in the study area is recharged from a similar source. The Schoeller diagram also showed the gradual increase in concentration of the major ions with depth. This leads to salinization in the deep boreholes. The oxygen and hydrogen isotope compositions in the groundwater samples suggest that groundwater recharge is of meteoric origin with few samples showing evidence of evaporation. An average deuterium excess of rainfall of 14.2 ‰ was observed, which indicates the significance of kinetic evaporation due to low humidity conditions prevalent in the study area. The d-excess also indicates modern recharge along the foothills of the Akwapim-Togo Ranges.