Integrated assessment of heavy metal contamination and health risks in irrigation water, soil, and vegetables along the Dankran River, Bekwai Municipality, Ghana

Abstract

Industrial operations release significant amounts of pollutants into the ecosystem, introducing potential threats to both humans and wildlife. The study examined water contamination in the Bekwai Municipality, Ghana, with a focus on the Dankran River's irrigation water and its impact on the accumulation of toxic metals in agricultural soils and cultivated vegetables. Water, soil, and vegetable samples were analysed for physicochemical properties and heavy metal content using ICP-OES. While the electrical conductivity of the irrigation water (151.58 ± 62.35 μS/cm) and total dissolved solids (132.22 ± 51.88 mg/L) were safe, high levels of total suspended solids (2744.44 ± 1039.43 mg/L), colour (25353.33 ± 5707.37 Pt/Co), and turbidity (2916.67 ± 617.36 NTU) raised concerns for agricultural use. Chromium (0.42 ± 0.13 mg/L) and arsenic (0.38 ± 0.13 mg/L) concentrations in irrigation water exceeded WHO/FAO standards, and soil samples also showed high levels of these metals (chromium: 84.31 ± 36.40; arsenic: 59.90 ± 17.60), raising food safety concerns. Although heavy metal levels in vegetables generally met safety standards, arsenic was consistently above safe limits in cabbage and garden eggs. Heavy metal transfer from soil to vegetables was mostly low, except for cadmium, which showed moderate but safe transferability. The health risk assessment found no substantial risk to the local vegetable consumers, with nickel posing the lowest threat. Also, arsenic was the primary contributor to the health index and cancer risks. Sustainable water and soil management is crucial to prevent heavy metal contamination in agriculture, necessitating regular monitoring of surface water near small-scale mining and waste disposal sites.