Abstract
Agricultural activities are often associated with contamination of water, which resulted in high concentration of nutrients and trace metals in the shallow aquifer. Occurrence and distribution of nutrients and trace metals in the groundwater of intensively irrigated region of Luvuvhu catchment were carried out to determine the status of groundwater quality and its suitability for drinking. Groundwater samples were collected and analysed for physio-chemical parameters. The results suggest that the concentration of nutrients and trace metals in the groundwater are below the permissible limit of drinking water standards recommended by the World Health Organization and South African standards except pH, K, and Pb. Low pH (51%), potassium (31%), and lead (100%) restrict the groundwater usage for drinking. Relation between groundwater flow direction and EC, sulphate, nitrate, and ammonium contents indicate that it is mostly constant towards the center of the study area, but sudden enrichment is noticed in the downstream. Silica and fluoride have increased along with the direction of groundwater flow. Trace metals (B, Pb, and Zn) show decreasing trend in the flow direction. However, pH, K, Li, Cr, and phosphate concentrations do not show significant variation along the flow direction. Positive relation between nitrate, EC, sulphate, and ammonium implies that groundwater quality is affected by the surface contamination sources, and mostly from irrigation return flow, through the application of fertilizers and organic manures. However, groundwater with high silica and fluoride also has high nitrate, which justify that wastewater infiltration from surface has triggered the mineral dissolution in the vadose. Trace metals does not correlate with nitrate. High concentrations of trace metals are recorded with low nitrate, which implies that metals are derived from mineral weathering. However, boron concentrations in few wells show positive relation with nitrate, which justified the impact of natural sources and irrigational activities.