Total mercury and methylmercury accumulation in wild plants grown at wastelands composed of mine tailings: Insights into potential candidates for phytoremediation
2018
Qian, Xiaoli | Wu, Yonggui | Zhou, Hongyun | Xu, Xiaohang | Xu, Zhidong | Shang, Lihai | Qiu, Guangle
Total mercury (THg) and methylmercury (MMHg) were investigated in 259 wild plants belonging to 49 species in 29 families that grew in heavily Hg-contaminated wastelands composed of cinnabar ore mine tailings (calcines) in the Wanshan region, southwestern China, the world's third largest Hg mining district. The bioconcentration factors (BCFs) of THg and MMHg from soil to roots ([THg]ᵣₒₒₜ/[THg]ₛₒᵢₗ, [MMHg]ᵣₒₒₜ/[MMHg]ₛₒᵢₗ) were evaluated. The results showed that THg and MMHg in both plants and soils varied widely, with ranges of 0.076–140 μg/g THg and 0.19–87 ng/g MMHg in roots, 0.19–106 μg/g THg and 0.06–31 ng/g MMHg in shoots, and 0.74–1440 μg/g THg and 0.41–820 ng/g MMHg in soil. Among all investigated species, Arthraxon hispidus, Eremochloa ciliaris, Clerodendrum bunge, and Ixeris sonchifolia had significantly elevated concentrations of THg in shoots and/or roots that reached 100 μg/g, whereas Chenopodium glaucum, Corydalisedulis maxim, and Rumex acetosa contained low values below 0.5 μg/g. In addition to the high THg concentrations, the fern E. ciliaris also showed high BCF values for both THg and MMHg exceeding 1.0, suggesting its capability to extract Hg from soils. Considering its dominance and the tolerance identified in the present study, E. ciliaris is suggested to be a practical candidate for phytoextraction, whereas A. hispidus is identified as a potential candidate for phytostabilization of Hg mining-contaminated soils.
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