环境水体中甲基汞光化学降解机理  

Photodegradation mechanism of methyl mercury in environmental waters

作　　者：邰超[1,2] 吴浩贤 李雁宾[4] 阴永光[3] 毛宇翔[1] 蔡勇[2,3] 江桂斌[3] TAI Chao WU HaoXian LI YanBin YIN YongGuang MAO YuXiang CAI Yong JIANG GuiBin(Institute of Resources and Environment, Henan Polytechnic University, Jiaozuo 454000, China Department of Chemistry and Biochemistry, Florida International University, Miami 33199, USA State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China)

机构地区：[1]河南理工大学资源环境学院,焦作454000 [2]Department of Chemistry and Biochemistry,Florida International University,Miami 33199,USA [3]中国科学院生态环境研究中心,环境化学与生态毒理学国家重点实验室,北京100085 [4]中国海洋大学海洋化学理论与工程技术教育部重点实验室,青岛266100

出　　处：《科学通报》2017年第1期70-78,共9页Chinese Science Bulletin

基　　金：国家自然科学基金(21120102040,21377120,21377035);国家重点基础研究发展计划(2013CB430002)资助

摘　　要：为进一步阐明甲基汞(MeHg)在环境水体中的光化学降解机理,选择海水、溪水以及可溶性有机质(dissolved organic matter,DOM)水溶液为研究对象,采用通氮通氧、清除剂添加和竞争性配体添加等方法,研究了MeHg在不同水体中的光降解情况.研究结果表明,所研究水体中Me Hg光降解均存在通氮促进而通氧抑制的情况,添加羟基自由基和水合电子清除剂对MeHg光降解没有明显影响,而叠氮化钠的加入则会明显抑制MeHg的光降解,其原因不是因为叠氮化钠清除了DOM光化学反应产生的单线态氧,而是因为叠氮化钠破坏了MeHg-DOM配合物;MeHg/DOM比值对MeHg光降解具有较大影响,MeHg在DOM水溶液中的光降解速率常数随MeHg/DOM比值的升高先基本保持不变、后迅速升高、然后迅速降低;而含巯基配体半胱氨酸存在下,甲基汞能够较快光降解,但在暗反应或者有竞争性配体N_3^-条件下,甲基汞光降解被抑制.以上实验结果表明,MeHg-DOM配合物经由分子内电子转移而引起的直接光解可能是一般环境水体中甲基汞光降解的一个普适性机理.Photodegradation is the major pathway of methyl mercury （MeHg） degradation in surface water. However, the mechanism underlying MeHg photodegradation is still not completely understood. Previous reports suggest four potential pathways are responsible for MeHg photodegradation, including direct photodegradation, hydroxyl radical dominant indirect photodegradation, singlet oxygen dominant indirect photodegradation, and comprehensive action of various free radicals/reactive oxygen species （ROS）. Recently, we reported that dissolved organic matter （DOM）-MeHg complex play the dominant role in the photodegradation of MeHg in the Florida Everglades wetland water. Another very different pathway, involving direct photodegradation of MeHg- DOM complexes via intramolecular electron transfer, was proposed as the dominant mechanism for MeHg photodegradation in the Everglades water. Taking the differences in water chemistry in aquatic system into consideration, MeHg photodegradation in different waters should be investigated furtherly to inspect the dominant mechanism for MeHg photodegradation in normal aquatic system. In this study, based on our experimental results reported about the methyl mercury （MeHg） photodegradation in the Everglades wetland water, MeHg photodegradation in different other typical waters, including sea water, creek water and DOM contained solution were studied by the methods of N2/O2 purging and scavengers adding for further understanding of MeHg photodegradation mechanism. The influence of MeHg/DOM ratio and different MeHg ligands adding on MeHg photodegradation were also investigated. It was found that MeHg photodegradation rate constant in sea water （（17.95±0.70）×10^-3 E^-1m^2）, creek water （（13.62±0.75）×10^-3 E^-1m^2） and DOM contained solution （（6.08±0.33）×10^-3 E^-1 m^2） differed greatly. However, the influences of N2/O2 purging and scavengers adding on MeHg photodegradation in three waters were very similar to that in the Everglades water previously re

关 键 词：甲基汞 光降解 可溶性有机质 自由基 机理 

分 类 号：X52[环境科学与工程—环境工程]