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厌氧条件下可溶性有机质对汞的还原与氧化作用
摘要点击 130  全文点击 62  投稿时间:2018-04-27  修订日期:2018-05-04
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中文关键词    可溶性有机质  还原  氧化  厌氧条件
英文关键词  mercury  dissolved organic matter  reduction  oxidation  anaerobic conditions
作者单位E-mail
卞永荣 中国科学院水利部成都山地灾害与环境研究所, 中国科学院山地表生过程与生态调控重点实验室, 成都 610041
中国科学院大学, 北京 100049
中国科学院南京土壤研究所, 中国科学院土壤环境与污染修复重点实验室, 南京 210008 
yrbian@issas.ac.cn 
顾宝华 美国橡树岭国家实验室环境科学系, 橡树岭 37830  
朱波 中国科学院水利部成都山地灾害与环境研究所, 中国科学院山地表生过程与生态调控重点实验室, 成都 610041  
程虎 中国科学院大学, 北京 100049
中国科学院南京土壤研究所, 中国科学院土壤环境与污染修复重点实验室, 南京 210008 
 
谷成刚 中国科学院南京土壤研究所, 中国科学院土壤环境与污染修复重点实验室, 南京 210008  
杨兴伦 中国科学院南京土壤研究所, 中国科学院土壤环境与污染修复重点实验室, 南京 210008  
宋洋 中国科学院南京土壤研究所, 中国科学院土壤环境与污染修复重点实验室, 南京 210008  
王芳 中国科学院南京土壤研究所, 中国科学院土壤环境与污染修复重点实验室, 南京 210008  
叶茂 中国科学院南京土壤研究所, 中国科学院土壤环境与污染修复重点实验室, 南京 210008  
蒋新 中国科学院南京土壤研究所, 中国科学院土壤环境与污染修复重点实验室, 南京 210008  
中文摘要
      在沉积物、湿地和淹水的水稻土中天然可溶性有机质(DOM),如胡敏酸(HA)和富里酸(FA)处于还原状态,其介导Hg(Ⅱ)的还原,影响汞的转化及地球化学循环.本文通过模拟黑暗厌氧环境,研究还原态HA与FA对Hg(Ⅱ)的还原.结果表明,还原态HA与FA的还原容量高于对照氧化态HA与FA.还原态HA与FA对Hg(Ⅱ)的还原最佳浓度分别是0.2 mg·L-1和1.5 mg·L-1.而高于最佳浓度时,由于发生巯基竞争性络合作用,抑制Hg(Ⅱ)的还原;特别是还原态HA大于5 mg·L-1时,不能还原Hg(Ⅱ)为Hg(0).还原态HA与FA对Hg(Ⅱ)的还原反应动力学表明:有机碳(DOC)与Hg(Ⅱ)摩尔比DOC:Hg(Ⅱ)=400:1时,还原反应速率IHSS-HA > FRC-HA > FRC-FA;高摩尔比[DOC:Hg(Ⅱ)=10000:1]时,还原态HA对Hg(Ⅱ)的还原反应停止,甚至向相反方向进行.还原态HA与FA对Hg(0)氧化结果表明,当还原态HA与FA浓度分别增加至5 mg·L-1和10 mg·L-1时,样品中检测不到Hg(0),还原态HA与FA对Hg(0)发生诱导性氧化络合作用.在汞的氧化还原与络合作用中,还原态DOM扮演双重角色,影响活性汞的可利用性,进而影响微生物汞的甲基化.
英文摘要
      In sediments, wetlands, and flooded paddy soils, natural organic matter (DOM), such as humic acid (HA) and fulvic acid (FA), exist in a reduced state and mediate the reduction of Hg(Ⅱ) and affect the transformation of mercury and geochemical cycles. This study simulated a dark anaerobic environment to study the reduction of Hg(Ⅱ) by reduced HA and FA. Compared to oxidized HA and FA, the reduction capacity of the reduced HA and FA for Hg(Ⅱ) were higher. The optimal concentrations of reduced HA and FA to reduce Hg(Ⅱ) to Hg(0) were 0.2 mg·L-1 and 1.5 mg·L-1, respectively. The reduction quantity of Hg(Ⅱ) was enhanced with the increased concentration of reduced HA and FA at a lower than optimal concentration, whereas the reduction quantity of Hg(Ⅱ) decreased with increasing concentration of reduced HA and FA at a higher than optimal concentration due to the occurrence of thiol-competitive complexation. Hg(Ⅱ) was not reduced at a reduced HA concentration of 5 mg·L-1. The kinetics results of Hg(Ⅱ) reduction demonstrated that the reduction rates were IHSS-HA > FRC-HA > FRC-FA at a low molar ratio (dissolved organic carbon (DOC):Hg(Ⅱ)=400:1). The reduction of Hg(Ⅱ) by the reduced HA stopped or processed in the opposite direction at a high molar ratio (DOC:Hg(Ⅱ)=10000:1). The quantity of Hg(0) decreased with increasing HA concentration. Furthermore, as the concentrations of reduced HA and FA were increased to 5 mg·L-1 and 10 mg·L-1, respectively, no Hg(0) was detected in the samples. The experiment of the recovery confirmed that reduced HA and FA reacted with Hg(0). Additionally, reduced HA, FA, and Hg(0) induced oxidative complexation with sulfhydryl or disulfide bonds. Reduced DOM played a dual role in Hg redox reactions, affecting the availability of active Hg, which, in turn, affected the methylation of microbial Hg.

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