Appraisal of lead (Pb) contamination and potential exposure risk associated with agricultural soils and some cultivated plants in gold mines

Abstract

Background: Artisanal gold mining has been one of the major contributors to soil pollution. These types of soil have potential environmental implications and varying degrees of health risk due to agricultural product cultivation. The contamination level of Pb in soils under cultivation by maize and spinach from gold mines in Abare, Dareta and Bagega mines of Anka local government Zamfara state was examined. Three levels of soil depths (0–21, 21–40 and 41–60 cm) from study sites were considered for vertical distributions of the Pb. The samples were digested and analyzed using flame atomic absorption spectrophotometry (Varian model-AA240FS). Results: The total Pb concentration ranges from 326.2 to 383.43 (Abare), 67.74–76.44 (Bagega) and 17.88–42.00 mg/kg (Dareta), which are all within the environmental protection agency (EPA) 400 mg/kg permissible limits, while only those analyzed from Abare were above the 85 mg/kg department of petroleum resources of Nigeria (DPR) threshold. From the result, the spinach grown in those areas exceeded the FAO/WHO 0.3 mg/kg threshold. Conclusion: Additionally, all study sites from all areas revealed the highest Pb concentrations at a 0–20 cm soil depth. This study further indicates all the soils from these areas are within safety limits based on the single pollution index (SPI) and Nemerow composite pollution index (NCPI). This information will significantly help provide greater insight into developing more effective remediation strategies for the affected localities. More research is needed into the speciation, chemical forms, bioavailability, and biogeochemical mechanisms that influence Pb mobility in those areas.