School of Environment, Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety & MOE Key Laboratory of Theoretical Chemistry of Environment, South China Normal University, Guangzhou 510006, China.
Department of Civil and Environmental Engineering, Water Technology Lab, Hong Kong Branch of Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China.
J Hazard Mater. 2021 Aug 5;415:125691. doi: 10.1016/j.jhazmat.2021.125691. Epub 2021 Mar 19.
Mine-polluted wastewater with mercury (Hg) poses severe environmental pollution since Hg(II) can be converted to highly neurotoxic methylmercury (MeHg) under anaerobic conditions. Previous studies on Hg methylation have focused on aquatic sediments, but few have investigated the MeHg formation in water layers containing algae. In this study, we investigated the dynamic effect of algae on Hg methylation throughout the lifetime of algae. We found that Chlorella pyrenoidosa was a non-methylating alga and exhibited good tolerance to Hg stress (1-20 μg/L); thus Hg(II) could not inhibit the process of eutrophication. However, the presence of C. pyrenoidosa significantly enhanced the Hg methylation by Geobacter sulfurreducens PCA. Compared to the control sample without algae, the MeHg production rate of algae-bacteria samples remarkably exacerbated by 62.3-188.3% with the algal growth period at cell densities of 1.5 × 10-25 × 10 cells/mL. The increase of algal organic matter and thiols with the algal growth period resulted in the exacerbation of MeHg production. The Hg methylation was also enhanced with the presence of dead algae, of which the enhancement was ~62.4% lower than that with the presence of live algae. Accordingly, the potential mechanism of Hg methylation in a freshwater algae-bacteria symbiotic system throughout the algal lifetime was proposed.
受汞（Hg）污染的矿山废水会造成严重的环境污染，因为在厌氧条件下，Hg(II) 可转化为具有高度神经毒性的甲基汞（MeHg）。先前关于 Hg 甲基化的研究主要集中在水生沉积物上，但很少有研究调查含有藻类的水层中 MeHg 的形成。在这项研究中，我们研究了藻类对整个藻类生命周期 Hg 甲基化的动态影响。我们发现，栅藻是一种非甲基化藻类，对 Hg 胁迫（1-20μg/L）具有良好的耐受性；因此，Hg(II) 不能抑制富营养化过程。然而，栅藻的存在显著增强了脱硫弧菌 PCA 的 Hg 甲基化作用。与没有藻类的对照样品相比，藻类-细菌样品中的 MeHg 生成速率在藻类生长阶段以 1.5×10-25×10 细胞/mL 的细胞密度显著增加了 62.3-188.3%。随着藻类生长周期的延长，藻类有机物质和硫醇的增加导致 MeHg 生成加剧。Hg 甲基化也随着死藻的存在而增强，其增强程度比活藻存在时低约 62.4%。因此，提出了淡水藻类-细菌共生系统中整个藻类生命周期 Hg 甲基化的潜在机制。
