研究报告
孙荣国,张成,王定勇.长寿湖水体甲基汞光化学降解特征[J].环境科学学报,2016,36(4):1137-1144
长寿湖水体甲基汞光化学降解特征
- Photodegradation of methylmercury in the water body of Changshou Lake
- 基金项目：国家重点基础研究发展规划(973)项目(No.2013CB430004);国家自然科学基金(No.41373113,41173116);中央高校基本科研业务费项目(No.XDJK2013C155);贵州师范大学2014年博士科研启动项目
- 作者
- 单位
- 孙荣国
- 1. 贵州师范大学化学与材料科学学院, 贵阳 550001;2. 西南大学资源环境学院, 三峡库区生态环境教育部重点实验室, 重庆 400715
- 张成
- 西南大学资源环境学院, 三峡库区生态环境教育部重点实验室, 重庆 400715
- 王定勇
- 西南大学资源环境学院, 三峡库区生态环境教育部重点实验室, 重庆 400715
- 摘要：为明确长寿湖水体甲基汞(MMHg)光化学降解特征,采用硼硅玻璃瓶对水样进行原位培养,探讨了长寿湖水体MMHg光化学降解的季节差异性及垂直变化特征,分析了不同波段光波对MMHg光化学降解反应的贡献,并估算了MMHg光化学降解的通量.结果发现,在光的作用下,长寿湖水体表层MMHg会发生明显的降解反应,未发现明显的净甲基化结果.在水体表层,夏季MMHg光化学降解速率最快((6.10±0.38)×10-3E-1·m2),其次为春季((4.90±0.24)×10-3E-1·m2),秋冬季节的降解速率较低,分别为(3.10±0.19)×10-3E-1·m2和(2.60±0.12)×10-3E-1·m2;UV-A、UV-B和可见光(PAR)对表层水体MMHg光化学降解反应的贡献分别为49%~52%、21%~31%和21%~34%.MMHg光化学降解速率随水深增加而逐步衰减,其中,UV-B引发的光化学降解反应速率衰减最快,其次为UV-A.对整个水体而言,PAR对MMHg光化学降解的贡献最大(67%~77%),其次为UV-A(25%~31%),UV-B的贡献最小(4.3%~8.1%).夏、秋、冬和春4个季节的MMHg日降解通量分别为7.2、0.73、1.1和5.9ng·m-2·d-1,年降解通量估算为1.5μg·m-2·a-1.可见,长寿湖水体MMHg光化学降解反应具有明显的季节和水深剖面变化特征,不同波段光波对降解反应的贡献有较大的差异.
- Abstract：In situ incubation experiments were conducted to investigate the temporal and spatial characteristics of methylmercury (MMHg) photodegradation in the water body of Changshou Lake. We discussed the photodegradation features of MMHg among different seasons and under vertical variations, analyzed the contributions of different wavelength spectrum to MMHg photodegradation, and estimated the fluxes of photoprocess. The results show that MMHg underwent a net photolysis, rather than a methylation process, under solar radiation. For surface water, MMHg photodegradation rate constants reach maxmumin summer ((6.10±0.38) ×10-3 E-1·m2), followed by spring ((4.90±0.24) ×10-3 E-1·m2), autumn ((3.10±0.19) ×10-3 E-1·m2), and winter ((2.60±0.12) ×10-3 E-1·m2). UV-A, UV-B, and photosynthetically active radiation (PAR) contributed 49%~52%, 21%~31%, and 21%~34% to photolysis process, respectively. MMHg photodegradation rate constants decreased with water depth, and the rate constant of UV-B radiation decreased most rapidly, followed by that obtained from UV-A radiation. For the entire water columns, PAR contributed most for MMHg degradation process (67%~77%), followed by UV-A (25%~31%), and UV-B (4.3%~8.1%). MMHg photodegradation fluxes for summer, autumn, winter, and spring were calculated to be 7.2, 0.73, 1.1, and 5.9 ng·m-2·d-1. The annual MMHg photodegradation flux was estimated to be 1.5 μg·m-2·a-1. Therefore, the process of MMHg photodegradation in Changshou Lake showed significant temporal variation characteristics, and the photolysis process contributed by different wavelength rangesvaried significantly.
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