Effect of Abiotic Factors on the Mercury Reduction Process by Humic Acids in Aqueous Systems  

作　　者：JIANG Tao WEI Shi-Qiang D.C.FLANAGAN LI Meng-Jie LI Xue-Mei WANG Qiang LUO Chang 

机构地区：[1]College of Resources and Environment,Department of Environment Science and Engineering,Southwest University [2]Chongqing Key Laboratory of Agricultural Resources and Environment [3]USDA-Agricultural Research Service,National Soil Erosion Research Laboratory

出　　处：《Pedosphere》2014年第1期125-136,共12页土壤圈（英文版）

基　　金：Supported by the National Natural Science Foundation of China(No.40971147/D010503);the China Postdoctoral Science Foundation(No.2013M542238);the Fundamental Research Funds for The Central Universities,China(No.XDJK2013C151);the Ph.D.Initiation Fund of Southwest University,China(No.SWU112098)

摘　　要：As a global pollutant process, the reduction of mercury （Hg） is especially important. One pathway is through an abiotic reduction with humic acids （HAs）, which is controlled by different factors, including initial Hg and HA concentrations, pH, temperature and light. In this study, three humic acids were selected to illustrate the Hg2＋ abiotic reduction mechanisms by HAs, and to identify the key limiting factors for reduction rates and amounts. In addition, the initial status of the HAs as a solid or in an aqueous solution were also compared, to help explain why HAs show different dominant characteristics （e.g. complexation or reduction） in the reaction process with Hg. Results indicated that HAs were able to reduce Hg abiotically. Higher initial Hg, higher HA concentrations and either high （8.1） or low （3.6） solution pH decreased the HA reduction capacity. In addition, Hg~ production rates increased with increasing temperature, and the same trend was observed with light exposure. Humic acids added as an aqueous solution resulted in significantly greater HgO production than addition as a bulk solid. Finally, the Hg reduction rate and capacity varied significantly （P 〈 0.05） with HAs from different sources. These findings helped to explain why HAs showed different dominant characteristics （e.g. complexation or reduction） in the reaction process with of Hg2＋ reduction, which indicated that humic substances in sink or a source for Hg. Hg, and evidentially demonstrated the existence of a possible pathway natural environments, especially in water bodies, could act either as aAs a global pollutant process,the reduction of mercury(Hg)is especially important.One pathway is through an abiotic reduction with humic acids(HAs),which is controlled by different factors,including initial Hg and HA concentrations,pH,temperature and light.In this study,three humic acids were selected to illustrate the Hg^(2+)abiotic reduction mechanisms by HAs,and to identify the key limiting factors for reduction rates and amounts.In addition,the initial status of the HAs as a solid or in an aqueous solution were also compared,to help explain why HAs show different dominant characteristics(e.g.complexation or reduction)in the reaction process with Hg.Results indicated that HAs were able to reduce Hg abiotically.Higher initial Hg,higher HA concentrations and either high(8.1)or low(3.6)solution pH decreased the HA reduction capacity.In addition,Hg°production rates increased with increasing temperature,and the same trend was observed with light exposure.Humic acids added as an aqueous solution resulted in significantly greater Hg°production than addition as a bulk solid.Finally,the Hg reduction rate and capacity varied significantly(P<0.05)with HAs from different sources.These findings helped to explain why HAs showed different dominant characteristics(e.g.complexation or reduction)in the reaction process with Hg,and evidentially demonstrated the existence of a possible pathway of Hg^(2+)reduction,which indicated that humic substances in natural environments,especially in water bodies,could act either as a sink or a source for Hg.

关 键 词：abiotic reduction COMPLEXATION humic substance natural organic matter 

分 类 号：O614.243[理学—无机化学]