title: Photo-degradation of monomethylmercury in the presence of chloride ion.
abstract: Photo-degradation (PD) of monomethylmercury (MMHg) is recognized as the most important process in mercury cycling that maintains MMHg at low concentration in water systems. Chloride ion (Cl(-)) is present widely in ecosystems and it may have an effect on MMHg PD. In this investigation, MMHg PD with various Cl(-) concentrations under different light radiation intensity and wavelength were performed in a quartz cylinder reactor. Various light radiations were obtained from xenon and ultraviolet (UV) bulbs. The results showed that the first order reaction coefficient decreased (1.35-0.37 h(-1)) with Cl(-) concentrations, and increased (0.14-0.76 h(-1)) with UV-B radiation intensity. The wavelength mediated PD rates varied from 0.29 h(-1) to 0.96 h(-1). The peak emission of Hg(0) was excited by UV-B radiation and Hg(0) flux of the reactions without Cl(-) (94.06 ng) was higher than that with Cl(-) by 1-4 times. All the results suggest that Cl(-) could block MMHg PD and subsequently influence the end products from PD. The wavelength and light intensity have a significant effect on MMHg PD and Hg(0) emission. Calculation of MMHg species (%) at initial and terminal time with various Cl(-) concentrations show that MMHg species changed by Cl(-) complexation and thus result in different PD mechanisms and pathways.
authors: Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment (Ministry of Education), College of Resource and Environment, Southwest University, Chongqing 400715, China.
authors: Rongguo
authors: R
authors: Sun
authors: Dingyong
authors: D
authors: Wang
authors: Yutao
authors: Y
authors: Zhang
authors: Wen
authors: W
authors: Mao
authors: Tong
authors: T
authors: Zhang
authors: Ming
authors: M
authors: Ma
authors: Cheng
authors: C
authors: Zhang
mesh_terms: D002384:Catalysis; D002712:Chlorides / Q000737:chemistry*; D008027:Light; D008767:Methylmercury Compounds / Q000737:chemistry*; D010782:Photolysis / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D002712:Chlorides; D008767:Methylmercury Compounds