Thermodynamic modelling of the chemical speciation of mercury and methylmercury under sulfidic conditions in boreal wetland soils
2017 (English)Other (Other academic)
Boreal wetlands have been identified as environmentsin which inorganic divalent mercury (HgII) is transformed to methylmercury (MeHg) by anaerobic microbes. In order to understand this transformation and the mobility and transport of HgII and MeHg, factors and conditions in control of the solubility and chemical speciation of HgII and MeHg need to be clarified. Here we explore the ability of thermodynamic models to simulate measuredsolubility of HgII and MeHg in different types of boreal wetland soils.With the input of measured concentrations of MeHg, sulfide, eight low molecular mass thiols and thiol groups associated with naturalorganic matter (NOM), as determined by sulfur K-edge X-rayabsorption near-edge structure (XANES) spectroscopy and Hg LIII-edgeextended X-ray absorption fine structure spectroscopy (EXAFS),the model could accurately predict porewater concentrations of MeHg in the wetlands. A similar model for HgII successfully predicted the average level of its concentration in the porewaters, but the variability among samples, driven mainly by the concentration of aqueous inorganic sulfide, was predicted to be larger than measurements. The smaller than predicted variability in HgII solubility is discussed in light of possible formation of colloidal HgS(s) passing the 0.22 μm filters used to define the aqueous phase. The chemical speciation of the solid/adsorbed and aqueousphases were dominated by NOM associated thiol complexes for MeHg and by an equal contribution from NOM associated thiolsand HgS(s) for HgII.
Place, publisher, year, pages
American Chemical Society (ACS), 2017. , 9 p.
Analytical Chemistry, Analytisk kemi
IdentifiersURN: urn:nbn:se:umu:diva-133343DOI: 10.1021/acs.est.6b04622OAI: oai:DiVA.org:umu-133343DiVA: diva2:1087184