title: Role of Free Radicals/Reactive Oxygen Species in MeHg Photodegradation: Importance of Utilizing Appropriate Scavengers.
abstract: A variety of free radicals (FR)/reactive oxygen species (ROS) have been proposed to dominate methylmercury (MeHg) photodegradation, primarily based on the results of FR/ROS scavenger addition experiments. However, in addition to eliminating FR/ROS, the added scavengers may also affect the experimental results by altering some water chemical properties, resulting in a misleading assessment of the importance of FR/ROS. In this study, 20 common FR/ROS scavengers were evaluated in terms of their influence on light absorbance, pH, MeHg analysis, MeHg-dissolved organic matter (DOM) complexation, and the scavenger-induced degradation of MeHg. Only nine scavengers were identified to be appropriate for investigating MeHg photodegradation. By utilizing these appropriate scavengers, direct photodegradation of MeHg-DOM complexes was found to be the major pathway of MeHg photodegradation in Laoshan Reservoir water and Stone Old Beach seawater. In contrast, MeHg photodegradation in Ink River water primarily occurs through both ·OH and3DOM* mediated indirect pathways and direct photodegradation of MeHg-DOM complexes. The diverse pathways of MeHg photodegradation in the tested water may be due to differences in water chemical properties. A severe overestimation of the role of FR/ROS was observed when several improper but commonly used scavengers were adopted, highlighting the necessity of utilizing appropriate scavengers.
authors.affiliation: College of Chemistry and Chemical Engineering, Ocean University of China , Qingdao 266100, China.
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: Han
authors.affiliation: Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China , Qingdao 266100, China.|College of Chemistry and Chemical Engineering, Ocean University of China , Qingdao 266100, China.
authors.forename: Yanbin
authors.identifier: 0000-0003-1813-4173
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Chemistry and Chemical Engineering, Ocean University of China , Qingdao 266100, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: College of Chemistry and Chemical Engineering, Ocean University of China , Qingdao 266100, China.
authors.forename: Chang
authors.initials: C
authors.lastname: Liu
mesh_terms: D005609:Free Radicals; D008767:Methylmercury Compounds; D010782:Photolysis; D017382:Reactive Oxygen Species / Q000737:chemistry*; D014874:Water Pollutants, Chemical
chemical_list: D005609:Free Radicals; D008767:Methylmercury Compounds; D017382:Reactive Oxygen Species; D014874:Water Pollutants, Chemical