Distribution characteristics of Hg2+ and methylmercury in natural organic matter with different molecular weights

Abstract

Abstract Natural organic matter (NOM) is a very important environmental medium in the aquatic environment. Hg2+ and methylmercury (MeHg) in the aquatic environment are mostly present in the form by combining with NOM. The distribution characteristics of Hg2+ and MeHg affects their transport and transformation in the aquatic environment. However, the distribution characteristics in molecular weight fractionated natural organic matters (Mf-NOM) are still unclear. In this study, the distribution characteristics of Hg2+ and MeHg in Mf-NOM were studied by isotope tracer technology. We observed that when both Hg2+ and MeHg were distributed in Mf-NOM, Hg2+ tended to distribute in higher molecular weight Mf-NOM, while MeHg preferred to the lower ones. These distributions had a strong correlation with pH. They was also affected by thiol-containing small molecules, which can bind with both Hg2+ and MeHg to form a more stable substance. Moreover, the composition and pH of water play a key role in determining the distribution characteristics of Hg2+ and MeHg in actual environment.