Evaluating the concentration of heavy metals in effluent irrigated vegetables around industrial area of Abuja, Nigeria

This study assessed heavy metal concentrations in irrigated Amaranthus and Capsicum crops grown with effluent water from the Idu Industrial Area, Federal Capital Territory, Nigeria. Effluent water samples were collected from Salco, NIPRD, and Afrifab Steel Ltd, along with soil samples and irrigated crop parts (roots, shoots, leaves, and chili) during wet and dry seasons. Samples were analyzed for Cd, Cr, Cu, Fe, Pb, Zn, Ni, As, and Hg, and results were compared with NESREA and FAO limits for effluent water, soil, and food crops. The study revealed varying levels of heavy metals, with Cu, Fe, Zn, and Ni showing higher concentrations in dry-season soils and crops. Statistical analyses indicated no significant differences in heavy metal concentrations in effluent water, soils, and crops between seasons, with values within NESREA and FAO permissible limits. However, the concentration of heavy metals in soils showed a strong positive correlation with those in Amaranthus leaves (r = 0.9211) and Capsicum chili (r = 0.965), indicating soil as the primary contamination pathway for crops. The study concludes that although current heavy metal levels do not exceed regulatory limits, continuous irrigation with untreated effluent poses a risk of accumulation in soil and crops over time. It recommends that all industrial effluent should be collected and treated at a centralized plant following NESREA guidelines before being discharged into agricultural fields to safeguard food safety and environmental health.