Distribution, contamination, toxicity, and potential risk assessment of toxic metals in media from Arufu Pb–Zn–F mining area, northeast Nigeria

Abstract

Toxic metals exuding from mining remain a challenge to the environment and human health. This study investigated the distribution, contamination, toxicity, and potential risks of toxic metals in rocks, soils, sediments, and tailings from a typical Pb–Zn–F mineralization zone in Nigeria. In this study, 64 samples which include soils, stream sediments, mine tailings, rocks, and plants were collected. All samples were prepared in the laboratory using acceptable international procedures. Metals in media were chemically digested and analyzed using inductively coupled plasma-mass spectrometer. The concentration of metals in media was above their concentrations in background samples. The average concentration of As, Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn in soils of the area is 0.90 µg/g, 0.10 µg/g, 7.10 µg/g, 27.18 mg/kg, 8.90 mg/kg, 0.10 mg/kg, 8.10 mg/kg, 959.30 mg/kg, and 109.30 mg/kg respectively while their concentration in tailings is 5.17 mg/kg, 1.74 mg/kg, 23.40 mg/kg, 38.40 mg/kg, 19.60 mg/kg, 17.00 mg/kg, 1275.00 mg/kg, and 359.80 mg/kg, respectively. Pollution load index (PLI) values for metals are >1 indicating severe pollution in the area. Bioaccumulation and translocation factors were >1 and showed that metals were mobilized from the media to different parts of plants. Risk index (RI) showed that heavy metals posed strong to extreme ecological risks. The carcinogenic risk (CR) is >0.4 and non-CR is >1 for adults and children which implies exposure to high carcinogenic and non-CRs. We suggest that complete remediation of contaminated media be carried out in the area.