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Probing the DOM-mediated photodegradation of methylmercury by using organic ligands with different molecular structures as the DOM model.
- Source :
-
Water Research . Jul2018, Vol. 138, p264-271. 8p. - Publication Year :
- 2018
-
Abstract
- Photodegradation is the main depletion pathway for methylmercury (MeHg) in surface water. The formation of MeHg-dissolved organic matter (DOM) complexes has been found to be a key step in MeHg photodegradation. However, the major functional groups involved in the DOM-mediated process have yet to be clearly resolved. In this work, we systematically investigated the effects of DOM molecular structures on MeHg photodegradation by using a variety of organic ligands with different functional groups (e.g., thiosalicylate, thiophenol, and thioaniline). The results showed that thiol and phenyl groups may be the major functional groups governing DOM-mediated MeHg photodegradation, with photodegradation rates also dependent on the type (carboxyl, hydroxyl, and amino group) and position (ortho-, meta-, and para-) of other chemical substituents. The addition of “non-photochemically active” thiol ligands (e.g., mercaptoethanol and dithiothreitol) and high concentrations of Cl − can significantly inhibit the o-thiosalicylate-induced MeHg photodegradation, indicating that complexation of MeHg with these ligands is necessary for MeHg photodegradation. Sparging with O 2 had a negligible effect on MeHg photodegradation, while sparging with N 2 significantly enhanced MeHg photodegradation. This finding suggests that MeHg photodegradation may be a reductive process, which was further supported by identification of the degradation products of MeHg. A possible protonolysis mechanism of MeHg photodegradation in the presence of o-thiosalicylate was then proposed based on the findings of this study. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00431354
- Volume :
- 138
- Database :
- Academic Search Index
- Journal :
- Water Research
- Publication Type :
- Academic Journal
- Accession number :
- 129120764
- Full Text :
- https://doi.org/10.1016/j.watres.2018.03.055