Contamination, sources and risk assessments of metals in media from Anka artisanal gold mining area, Northwest Nigeria

摘要

Mining is a major human activity that has contributed significantly to high degree of environmental and human health degradation. This study was done to uncover the degree of contamination and risks associated with metals in environmental media collected from Anka area, Northwest Nigeria. A total of eighty-two (82) samples which include 42 soils, 22 stream sediments, 13 tailings and 5 plants were collected. Media were air-dried, pulverized and sieved to collect fine particles. They were digested and analyzed for toxic metal contents using High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometer (HPLC-ICPMS). Metals analyzed include As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, Zn and Fe. From the results, degree of contamination in samples were obtained using pollution indices, while ecological and health risks were calculated using acceptable risk indices. Average concentrations of metals in the soils were: As: 0.64 μg/g; Cr: 42.55 ug/g; Pb: 131.76 μg/g; Hg: 0.85 μg/g while in sediments, the average concentration were As: 15.46 μg/g; Cr: 111.82 μg/g; Pb: 2234.02 μg/ g; Hg: 2.12 μg/g. In tailings, the mean concentration were As: 4.79 μg/g; Cr: 96.95 μg/g; Pb: 2802.56 μg/g; Hg: 1.25 ug/g. Metals in plants are above acceptable limits. Metals in the media are both from geogenic and mining activities, and they pose high ecological risks. High carcinogenic (>10~(-4)) and non-carcinogenic (>1) health risks are associated with metals in media from this area. Further epidemiological studies should be carried to know the extent of occurrence of diseases associated with mining in the area.