Extremely Elevated Total Mercury and Methylmercury in Forage Plants in a Large-Scale Abandoned Hg Mining Site: A Potential Risk of Exposure to Grazing Animals

Ninety-five wild forage plants (belonging to 22 species of 18 families) and their corresponding rhizosphere soil samples were collected from wastelands a large-scale abandoned Hg mining region for total (THg) methylmercury (MeHg) analysis. The plant communities on the dominated by Asteraceae, Crassulaceae, Polygonaceae families. THg MeHg concentrations in varied widely range 0.10 13 mg/kg 0.19 23 μg/kg, respectively. Shoots Aster ageratoides showed highest average concentration 12 ± 1.1 mg/kg, while those subulatus had 7.4 6.1 μg/kg. Both aboveground parts exhibited positive correlations with (r = 0.70, P < 0.01) 0.68, roots; however, these not correlated soils. A. ageratoides, subulatus, S. brachyotus strong accumulation are concern herbivorous/omnivorous wildlife feeding livestock. Taking provisional tolerable weekly intake (PTWI) values IHg recommended Joint FAO/WHO Expert Committee Food Additives (JECFA Summary conclusions seventy-second meeting joint expert committee food additives Rome, Italy, 2010) human dietary exposure 4 ng/g into account, daily 65 kg animal grazing 1.0 (dry weight) would be between 190 13,200 μg, three five orders magnitude higher than permitted limit, suggesting potential risk exposure.