Factors affecting methylmercury distribution in surficial, acidic, base-metal mine tailings

被引：24

作者：

Winch, S. ^{[1
]}

Praharaj, T. ^{[1
]}

Fortin, D. ^{[1
]}

Lean, D. R. S. ^{[2
]}

机构：

[1] Univ Ottawa, Dept Earth Sci, Ottawa, ON K1N 6N5, Canada

[2] Univ Ottawa, Dept Biol, Ottawa, ON K1N 6N5, Canada

来源：

SCIENCE OF THE TOTAL ENVIRONMENT | 2008年 / 392卷 / 2-3期

基金：

加拿大自然科学与工程研究理事会;

关键词：

mine tailings; sulfate-reducing bacteria; mercury; methylmercury;

D O I：

10.1016/j.scitotenv.2007.12.008

中图分类号：

X [环境科学、安全科学];

学科分类号：

08 ; 0830 ;

摘要：

The most toxic form of Hg commonly of concern in the environment is methylmercury (MeHg), as it accumulates in living tissues and bioconcentrates in food webs. Sulfide-rich metal ores are often enriched in Hg, but little is known regarding the potential for Hg methylation in acidic tailings produced from these ores. This study examined acidic tailings from four mines in northern Ontario, Canada, to determine whether they could be an important source of MeHg to downstream environments. Where sulfate reducing bacteria (SRB) were abundant and active in pH-circumneutral, unoxidized layers (Potter mine), negligible MeHg was detected. By contrast, a zone of active sulfate reduction found in the acidic, oxidizing, surficial layers of tailings from the Kidd Metsite contained the highest concentrations of MeHg in bulk tailings (12.1 nmol kg(-1) dry wt. of sediment) and porewaters (88 pM) measured in this study. Cell count estimates of SRB by the "most-probable-number" (MPN) method were low in these surficial tailings, suggesting that sulfate reducers from this environment were acidophilic and did not thrive under the pH-neutral conditions of the MPN incubations. A later study of bacterial DNA from these tailings produced evidence of a novel Deltaproteobacterium which has only previously been detected in acid mine drainage environments. Further research will be necessary to determine whether this Deltaproteobacterium is a sulfate reducer and/or an efficient Hg methylator. Surface water concentrations of MeHg did not exceed Canadian water quality guidelines at any of the sites sampled, but one site (Broulan) featured total Hg (Hg-T) concentrations of 838 pM in filtered samples, far in excess of recommended levels. Trends in surface water MeHg and Hg-T reflected corresponding values in porewaters from the same sites, indicating that concentrations of these substances in tailings influence surface water concentrations. (C) 2007 Elsevier B.V. All rights reserved.

引用

页码：242 / 251

页数：10