Abstract Ninety-five wild forage plants (belonging to 22 species of 18 families) and their corresponding rhizosphere soil samples were collected from wastelands of a world large-scale abandoned Hg mining region for total Hg (THg) and methylmercury (MeHg) analysis. The forage plant communities on the wastelands were dominated by the Asteraceae , Crassulaceae and Polygonaceae families. The THg and MeHg concentrations in the forage plants varied widely and were in the range of 0.10 to 13 mg/kg and 0.19 to 23 μg/kg, respectively. Shoots of Aster ageratoides showed the highest average THg concentration of 12±1.1 mg/kg, while those of Aster subulatus had the highest average MeHg concentrations of 7.4±6.1 μg/kg. Both the THg and MeHg concentrations in the aboveground plant parts exhibited positive correlations with the THg (r=0.70, P<0.01 ) and MeHg (r=0.68, P<0.01 ) concentrations in the roots but these were not correlated with the THg and MeHg concentrations in their rhizosphere soils. The species A. ageratoides, A. subulatus, and S. brachyotus showed strong accumulation of Hg and are of concern for herbivorous/omnivorous wildlife and feeding livestock. Taking the provisional tolerable weekly intake (PTWI) values for IHg recommended by the JECFA (2010) for human dietary exposure of 4 ng/g into account, grazing on 1.0 kg of forage (dry weight) by a 65 kg animal would mean that the daily intake of IHg was between 190-13200 μg, which reaches 3-5 order of magnitude higher than the permitted limit, suggesting a potential risk of exposure.
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