title: Effects of natural water constituents on the photo-decomposition of methylmercury and the role of hydroxyl radical.
abstract: Photo-decomposition of methylmercury (MeHg) in surface water is thought to be an important process that reduces the bioavailability of mercury (Hg) to aquatic organisms. In this study, photo-initiated decomposition of MeHg was investigated under UVA irradiation in the presence of natural water constituents including NO3(-), Fe(3+), and HCO3(-) ions, and dissolved organic matter such as humic and fulvic acid. MeHg degradation followed the pseudo-first-order kinetics; the rate constant increased with increasing UVA intensity (0.3 to 3.0 mW cm(-2)). In the presence of NO3(-), Fe(3+), and fulvic acid, the decomposition rate of MeHg increased significantly due to photosensitization by reactive species such as hydroxyl radical. The presence of humic acid and HCO3(-) ions lowered the degradation rate through a radical scavenging effect. Increasing the pH of the solution increased the degradation rate constant by enhancing the generation of hydroxyl radicals. Hydroxyl radicals play an important role in the photo-decomposition of MeHg in water, and natural constituents in water can affect the photo-decomposition of MeHg by changing radical production and inhibition.
authors: Department of Environmental Health, School of Public Health, Seoul National University, Seoul 151-742, Republic of Korea.
authors: Moon-Kyung
authors: MK
authors: Kim
authors: Kyung-Duk
authors: KD
authors: Zoh
mesh_terms: D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D008745:Methylation; D008767:Methylmercury Compounds / Q000737:chemistry*; D055668:Photochemical Processes; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry*
chemical_list: D008767:Methylmercury Compounds; D014867:Water; D017665:Hydroxyl Radical