Hydrochemical characteristics of surface water and ecological risk assessment of sediments from settlements within the Birim River basin in Ghana

Noah Kyame Asare-Donkor,Japhet Opoku Ofosu,Anthony Apeke Adimado

doi:10.1186/s40068-018-0113-1

Noah Kyame Asare-Donkor, Japhet Opoku Ofosu + Show 1 more

Open Access

https://doi.org/10.1186/s40068-018-0113-1

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Abstract

BackgroundGeogenic and anthropogenic activities such as Artisanal and illegal gold mining continue to have negative impacts on the environment and river basins in China. This work studied the hydrogeochemical characteristics of surface water from the Birim River basin and assess the quality of water for human consumption and agricultural activities. In addition, the ecological risk assessment for Cd, Zn, Pb and As in sediment was evaluated using pollution indices.ResultsThe results show that the turbidity, temperature, colour and iron concentration in the water samples were above the World Health Organization guidelines. Multivariate analysis explained five components that accounted for 98.15% of the overall hydrogeochemistry and affected by anthropogenic and geogenic impacts. The surface water was observed to range from neutral to mildly acidic, with the dominance of HCO3−, Cl−, Ca2+, Mg2+, and Na+ in ionic strength. The Piper diagram reveals five major surface water types: Na–HCO3–Cl, Na–Cl–HCO3, Na–Ca–Mg–HCO3, Na–Ca–Mg–HCO3 and Ca–Na–Mg–HCO3. The Gibbs plot showed that the major ion chemistry of surface water was mostly influenced by atmospheric precipitation and the water quality index showed that the majority of the surface water from settlements within the Birim River basin were of poor quality for drinking and other domestic purposes. However, irrigation suitability calculations with reference to sodium adsorption ratio, residual sodium carbonate, and magnesium ratio values, together with Wilcox and USSL models indicated that the surface water within the area under study was suitable for agriculture. The potential ecological risk for single heavy metals pollution and potential toxicity response indices gave low to considerable ecological risks for the sediments, with greater contributions from Cd, Pb and As. Whilst geo-accumulation indices indicated that the sediments ranged from unpolluted to moderately polluted Modified degree of pollution and Nemerow pollution index calculations which incorporate multi-element effects, however, indicated no pollution.ConclusionThere are some levels of both potential ecological risks and health hazards in the study area. Hence continuous monitoring should be undertaken by the relevant agencies and authorities so that various interventions could be put in place to prevent the situation from deteriorating further in order to protect the inhabitants of the settlements within the Birim River basin.

Highlights

Geogenic and anthropogenic activities such as Artisanal and illegal gold mining continue to have neg‐ ative impacts on the environment and river basins in China
Based on the Eri results, the ecological risks associated with As, Zn and Pb are generally low whiles that associated with Cd are a considerable risk
The results of this study provided valuable information about the hydrochemistry and water quality of surface water as well as ecological risks of some heavy metal contents of sediment from different settlements within the Birim River basin

Summary

Introduction

Water resources are being enriched with metals, metalloids or ions, which often tend to be toxic to mankind as well as the natural environment (Lang et al 2006; Négrel et al 2006; Robinson and Ayotte 2006) Other geochemical activities, such as sorption, redox reactions, ion exchange, and complexation may alter it’s hydrogeochemistry and subsequently affect the water quality. The hydrogeochemical characterization may be accomplished via several techniques, and among them are the typical hydrogeochemical ratios, which can evaluate the dominant and origin processes of water resources (Zhu et al 2007), as well as multivariate statistical analysis (Saleem et al 2015; Purushothaman et al 2014) These two techniques may be valuable in identifying the factors that influence surface water chemistry, hydrogeological and complex geological systems

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