title: Implications of mercury speciation in thiosulfate treated plants.
abstract: Mercury uptake was induced in two cultivars of  Brassica juncea  under field conditions using thiosulfate. Analysis was conducted to better understand the mechanism of uptake, speciation of mercury in plants, and redistribution of mercury in the soil. Plant mercury and sulfur concentrations were increased after thiosulfate treatment, and a linear correlation between mercury and sulfur was observed. Mercury may be absorbed and transported in plants as the Hg-thiosulfate complex. The majority of mercury in treated plant tissues (two cultivars) was bound to sulfur in a form similar to β-HgS (66-94%). Remaining mercury was present in forms similar to Hg-cysteine (1-10%) and Hg-dicysteine (8-28%). The formation of β-HgS may relate to the transport and assimilation of sulfate in plant tissues. Mercury-thiosulfate complex could decompose to mercuric and sulfate ions in the presence of free protons inside the plasma membrane, while sulfide ions would be produced by the assimilation of sulfate. The concomitant presence of mercuric ions and S(2-) would precipitate β-HgS. The mercury concentration in the rhizosphere decreased in the treated relative to the nontreated soil. The iron/manganese oxide and organic-bound fractions of soil mercury were transformed to more bioavailable forms (soluble and exchangeable and specifically sorbed) and taken up by plants.
authors.affiliation: State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, People's Republic of China.
authors.forename: Jianxu
authors.initials: J
authors.lastname: Wang
authors.forename: Xinbin
authors.initials: X
authors.lastname: Feng
authors.forename: Christopher W N
authors.initials: CW
authors.lastname: Anderson
authors.forename: Heng
authors.initials: H
authors.lastname: Wang
authors.forename: Lirong
authors.initials: L
authors.lastname: Zheng
authors.forename: Tiandou
authors.initials: T
authors.lastname: Hu
mesh_terms: D001673:Biodegradation, Environmental / Q000187:drug effects; D018533:Biomass; D005591:Chemical Fractionation; D002681:China; D016018:Least-Squares Analysis; D008628:Mercury / Q000302:isolation & purification*; D009149:Mustard Plant / Q000187:drug effects* / Q000378:metabolism*; D009928:Organ Specificity / Q000187:drug effects; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D058441:Rhizosphere; D012987:Soil / Q000737:chemistry; D013455:Sulfur / Q000032:analysis; D013885:Thiosulfates / Q000494:pharmacology*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D012987:Soil; D013885:Thiosulfates; D013455:Sulfur; D008628:Mercury