Sulfidation of mercury(Hg)in Hg(Ⅱ)-dissolved organic matter(DOM)-sulfide(S(-Ⅱ))systems has crucial impacts on its transport,transformation,and bioavailability risks in food chains(e.g.,from fish to humans)under anox...Sulfidation of mercury(Hg)in Hg(Ⅱ)-dissolved organic matter(DOM)-sulfide(S(-Ⅱ))systems has crucial impacts on its transport,transformation,and bioavailability risks in food chains(e.g.,from fish to humans)under anoxic environments.Probing this process remains a significant challenge due to low Hg concentrations and poor sensitivity of conventional characterization methods.Here,we systematically identified nanoparticulate mercury sulfide(nano-HgS)formation in Hg(Ⅱ)-DOM-S(-Ⅱ)systems at nanomolar Hg(Ⅱ)levels and deciphered its environmental factors by integrating liquid chromatography(LC)-ICP-MS combined with ultrafiltration-transmission electron microscopy(TEM).Ultrafiltration-TEM with energy dispersive spectroscopy confirmed the spherical nano-Hg S(~5 nm)formation.Formation kinetics demonstrated a rapid formation of nano-HgS,followed by a slow size increase.Environmental factors,including pH,DOM,S(-Ⅱ),and Ca2+,modulated nano-HgS size distributions by altering surface charge interactions(e.g.,electrostatic repulsion),whereas natural ligands(Cl-,citrate,mercaptopropionic acid)showed negligible effects.Crucially,nano-HgS was the predominant Hg species in the Hg(Ⅱ)-DOM-S(-Ⅱ)systems,rather than dissolved HgS species(e.g.,HgSaq0 and HgS22-).Although nano-Hg S,especially aged nano-HgS exhibits lower methylmercury production than Hg(Ⅱ)-DOM complex at 24 h incubation by Geobacter sulfurreducens PCA,higher methylation for newborn nano-HgS at the initial 8 h further highlights the previously proposed“Trojan horse”mechanism of uptake followed by intracellular dissolution of nano-HgS.This work provides a significant analytical tool for accurately identifying and quantifying nano-HgS in the Hg(Ⅱ)-DOM-S(-Ⅱ)systems and highlights the importance of assessing the methylation of newborn nano-HgS because it may amplify Hg toxicity in food chains through providing higher methylation production.展开更多
基金supported by the National Key Research and Development Project(No.2020YFA0907400)the National Natural Science Foundation of China(Nos.22476206 and 22425606)。
摘要Sulfidation of mercury(Hg)in Hg(Ⅱ)-dissolved organic matter(DOM)-sulfide(S(-Ⅱ))systems has crucial impacts on its transport,transformation,and bioavailability risks in food chains(e.g.,from fish to humans)under anoxic environments.Probing this process remains a significant challenge due to low Hg concentrations and poor sensitivity of conventional characterization methods.Here,we systematically identified nanoparticulate mercury sulfide(nano-HgS)formation in Hg(Ⅱ)-DOM-S(-Ⅱ)systems at nanomolar Hg(Ⅱ)levels and deciphered its environmental factors by integrating liquid chromatography(LC)-ICP-MS combined with ultrafiltration-transmission electron microscopy(TEM).Ultrafiltration-TEM with energy dispersive spectroscopy confirmed the spherical nano-Hg S(~5 nm)formation.Formation kinetics demonstrated a rapid formation of nano-HgS,followed by a slow size increase.Environmental factors,including pH,DOM,S(-Ⅱ),and Ca2+,modulated nano-HgS size distributions by altering surface charge interactions(e.g.,electrostatic repulsion),whereas natural ligands(Cl-,citrate,mercaptopropionic acid)showed negligible effects.Crucially,nano-HgS was the predominant Hg species in the Hg(Ⅱ)-DOM-S(-Ⅱ)systems,rather than dissolved HgS species(e.g.,HgSaq0 and HgS22-).Although nano-Hg S,especially aged nano-HgS exhibits lower methylmercury production than Hg(Ⅱ)-DOM complex at 24 h incubation by Geobacter sulfurreducens PCA,higher methylation for newborn nano-HgS at the initial 8 h further highlights the previously proposed“Trojan horse”mechanism of uptake followed by intracellular dissolution of nano-HgS.This work provides a significant analytical tool for accurately identifying and quantifying nano-HgS in the Hg(Ⅱ)-DOM-S(-Ⅱ)systems and highlights the importance of assessing the methylation of newborn nano-HgS because it may amplify Hg toxicity in food chains through providing higher methylation production.