Analysis of Selected Potentially Harmful Metal Elements in Soils and Vegetables in Gold Mining Region: Case Study Evaluated in Kenya, Africa

Abstract

This study aimed to assess heavy metal and associated trace element contamination in soils and vegetables from artisanal gold mining areas in Migori County, Kenya. Soil concentrations were markedly elevated, with Pb (15.4–706 mg/kg), Cd (0.14–6.07 mg/kg), Ni (0.2–33.4 mg/kg), Cr (11.9–119.3 mg/kg), As (0.1–37.4 mg/kg), Zn (38–1454 mg/kg), Se (0.1–0.8 mg/kg), and Hg (0.51–1830 mg/kg) all exceeding international guideline values. Corresponding vegetable concentrations were as follows: Pb (0.17–71.3 mg/kg), Ni (0.2–111 mg/kg), Cr (2.4–244 mg/kg), As (1.2–399 mg/kg), Hg (0.22–35 mg/kg), Zn (11.2–67.4 mg/kg), and Se (0.1–5.7 mg/kg). Brassica oleracea var. capitata (cabbage) exhibited the highest uptake, while Amaranthus hybridus (smooth pigweed) showed the lowest. Estimated daily intake (EDI) values for Pb, Ni, Cr, As, Zn, and Hg exceeded FAO/WHO limits, with hazard quotients (HQ) > 1 for all metals and hazard index (HI) values between 15.6 and 30.4, indicating significant non-carcinogenic and carcinogenic risks. These findings highlight severe contamination linked to geological background and mining activity, underscoring the urgent need for regular monitoring and mitigation to protect food safety and public health.