Heavy metal accumulation and transfer between soils–plants–goats in a Mo-mining area

The effect of Mo mining on soil–plant–animal ecosystem heavy metal accumulation and migration has not been well investigated. In this work, soil, native plants, and goat hair samples were collected from mining, urban, and rural areas near a Mo-mining area in Luanchuan, China and analyzed for Mo, Pb, Cd, Cu, Zn, Ni, and Mn concentrations. Molybdenum had the largest pollution indices (soil heavy metal concentration/background value) among all metals. Although mining area soil had greater concentrations of all seven metals as compared to urban and rural areas, significant differences were only found for Cd (mining, 2.54; urban, 1.59; and rural, 1.85 mg kg⁻¹), Cu (73.4, 32.1, and 32.6 mg kg⁻¹), and Mo (109, 33.6, and 16.6 mg kg⁻¹). Setaria viridis had greater Mo concentrations in the mining area than the urban area, most plant samples had Mo concentrations >5 mg kg⁻¹, and mean plant Cu:Mo ratios were <4 in all three areas, both indicating potential Mo toxicity and Cu deficiency risks to herbivores. Goat hair Mo concentrations in both areas were greater, whereas the Cu:Mo ratios were lower than those found in the literature. Plants had greater bioconcentration factors (0.840–5.30) for soil Mo than other metals, whereas goat hair and grass Mo concentration ratios were <0.03, lower than most reported literature values. Results indicate Mo accumulation in soil, plants, and goat hair in the Mo-mining area; remediation measures may be needed to alleviate animal and potentially resident Mo stress.