title: Critical role of natural organic matter in photodegradation of methylmercury in water: Molecular weight and interactive effects with other environmental factors.
abstract: Photodegradation is the main depletion pathway of methylmercury (MeHg) in surface water. However, the underlying mechanism of MeHg photodegradation is still not well understood. In this study, the critical role of natural organic matter (NOM) from Suwannee River natural organic matter of the International Humic Substance Society, especially its molecular weight, and the impacts of other related environmental factors in MeHg photodegradation were investigated. We observed that MeHg cannot photo-degrade in de-ionized water, excluding the direct photodegradation of MeHg. While either NOM or Fe3+alone induced MeHg photodegradation, co-existing NOM significantly inhibited the Fe3+-induced degradation, highlighting the critical and complex role of NOM in MeHg photodegradation. Additionally, MeHg exhibited different photodegradation rates in the presence of molecular weight fractionated natural organic matter (Mf-NOM). More importantly, high concentration of NOM caused light attenuation significantly inhibited the photodegradation of MeHg, which was more significant for high molecular weight Mf-NOM. In the presence of Mf-NOM, MeHg photodegradation was also affected by light quality, pH and co-existing Cl-and NO3-. The study is helpful for a better understanding of the critical role of NOM and other environmental factors on MeHg photodegradation in surface water.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Yongguang
authors.initials: Y
authors.lastname: Yin
authors.affiliation: Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China.
authors.forename: Yanbin
authors.initials: Y
authors.lastname: Li
authors.affiliation: Institute of Environment and Health, Jianghan University, Wuhan 430056, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Cai
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. Electronic address: jfliu@rcees.ac.cn.
authors.forename: Jingfu
authors.initials: J
authors.lastname: Liu
mesh_terms: D006812:Humic Substances; D008767:Methylmercury Compounds / Q000737:chemistry*; D008970:Molecular Weight; D010782:Photolysis; D014867:Water; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D006812:Humic Substances; D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D014867:Water
keywords: Iron; Methylmercury; Molecular weight; Natural organic matter; Photodegradation