Spatial Variability, Bio-accumulation, and Health Risks of Heavy Metals in Wudil Agricultural Produce: Insights from MP-AES Quantification

This study quantified heavy metals contamination in peri-urban agricultural soils and vegetables from Wudil, Kano State, Nigeria, using Microwave Plasma–Atomic Emission Spectroscopy (MP-AES, Agilent 4210). Concentrations of Pb, Cd, Cu, Zn, and Cr in soils ranged from 0.25 to 1.16 mg/kg, while vegetable concentrations varied between 0.08 and 11.03 mg/kg, reflecting distinct metal-specific uptake patterns. Manganese (Mn) exhibited the highest accumulation in vegetables (7.58–11.03 mg/kg; mean 9.11 mg/kg), particularly in lettuce, whereas Chromium (Cr) showed moderate variability (0.08–0.85 mg/kg). Cadmium (Cd) and Lead (Pb) concentrations in vegetables remained comparatively low (Cd: 0.02–0.19 mg/kg; Pb: 0.05–0.41 mg/kg), yet their toxicological relevance was evident in elevated Estimated Daily Intake (EDI) and Target Hazard Quotient (THQ) values. Although THQ values for individual metals were generally < 1, but cumulative Hazard Index (HI) values for some vegetables exceeded the safety threshold (ΣTHQ = 1.01–1.80). Cancer Risk (CR) estimates for Cd and Cr surpassed the acceptable limit of 10⁻⁴, with pepper (CR = 0.0180) and spinach (CR = 0.0124) presenting the highest carcinogenic risk. Despite moderate soil contamination (PLI = 0.44), vegetable uptake significantly amplified human-health risks. These findings highlight the need for continuous monitoring, improved wastewater-irrigation management, and targeted public-health interventions to reduce long-term dietary exposure.