Pedosphere 24(1): 125--136, 2014
ISSN 1002-0160/CN 32-1315/P
©2014 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Effect of abiotic factors on the mercury reduction process by humic acids in aqueous systems |
JIANG Tao1,2, WEI Shi-Qiang1,2 , D. C. FLANAGAN3, LI Meng-Jie1, LI Xue-Mei1, WANG Qiang1,2 and LUO Chang1 |
1College of Resources and Environment, Department of Environment Science and Engineering, Southwest University, Chongqing 400716 (China)
2Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400716 (China)
3
USDA-Agricultural Research Service, National Soil Erosion Research Laboratory, West Lafayette, IN 47907-2077 (USA) |
| ABSTRACT |
| 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, Hg0 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 Hg0 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 Hg2+ reduction, which indicated that humic substances in natural environments, especially in water bodies, could act either as a sink or a source for Hg. |
| Key Words: abiotic reduction, complexation, humic substance, natural organic matter |
| Citation: Jiang, T., Wei, S. Q., Flanagan, D. C., Li, M. J., Li, X. M., Wang, Q. and Luo, C. 2014. Effect of abiotic factors on the mercury reduction process by humic acids in aqueous systems. Pedosphere. 24(1): 125-136. |
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