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Effects of mercury addition on microbial community composition and nitrate removal inside permeable reactive barriers
Environmental Pollution ( IF 8.9 ) Pub Date : 2018-07-07 , DOI: 10.1016/j.envpol.2018.07.017
Kenly Hiller-Bittrolff , Kenneth Foreman , Ashley N. Bulseco-McKim , Janina Benoit , Jennifer L. Bowen

Permeable reactive barriers (PRBs) remove nitrogen from groundwater by enhancing microbial denitrification. The PRBs consist of woodchips that provide carbon for denitrifiers, but these woodchips also support other anaerobic microbes, including sulfate-reducing bacteria. Some of these anaerobes have the ability to methylate inorganic mercury present in groundwater. Methylmercury is hazardous to human health, so it is essential to understand whether PRBs promote mercury methylation. We examined microbial communities and geochemistry in fresh water and sulfate-enriched PRB flow-through columns by spiking replicates of both treatments with mercuric chloride. We hypothesized that mercury addition could alter bacterial community composition to favor higher abundances of genera containing known methylating taxa and that the sulfate-rich columns would produce more methylmercury after Hg addition, due mainly to an increase in abundance of sulfate reducing bacteria (SRB). However, methylmercury output at the end of the experiment was not different from output at the beginning, due in part to coupled Hg methylation and demethylation. There was a transient reduction in nitrate removal after mercury addition in the sulfate enriched columns, but nitrate removal returned to initial rates after two weeks, demonstrating resilience of the denitrifying community. Since methylmercury output did not increase and nitrate removal was not permanently affected, PRBs could be a low cost approach to combat eutrophication.



中文翻译:

添加汞对可渗透反应性屏障内微生物群落组成和硝酸盐去除的影响

渗透性反应屏障(PRB)通过增强微生物反硝化作用从地下水中去除氮。PRB由为反硝化器提供碳的木片组成,但这些木片还支持其他厌氧微生物,包括硫酸盐还原菌。其中一些厌氧菌具有甲基化地下水中存在的无机汞的能力。甲基汞对人体健康有害,因此必须了解PRB是否会促进汞甲基化。我们通过用氯化汞加标两种处理的重复,检查了淡水和富硫酸盐的PRB流通柱中的微生物群落和地球化学。我们假设添加汞可能会改变细菌群落组成,从而有利于包含已知甲基化类群的属的较高丰度,并且富汞的柱在添加汞后会产生更多的甲基汞,这主要是由于减少硫酸盐的细菌(SRB)的丰度增加。但是,实验结束时甲基汞的输出与开始时的输出没有什么不同,这部分是由于Hg甲基化和去甲基化的耦合。在富硫酸盐的色谱柱中添加汞后,硝酸盐的去除量有短暂的减少,但是两周后硝酸盐的去除量恢复了初始速率,这表明了反硝化群落的复原力。由于甲基汞的产量没有增加并且硝酸盐的去除没有受到永久性的影响,因此PRB可能是一种对抗富营养化的低成本方法。

更新日期:2018-07-08
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