附着生物汞甲基化及其对水环境甲基汞归趋的影响

Mercury Methylation in Periphyton and Its Impact on the Fate of Methylmercury in Aquatic Environments

汞是一种重要的全球性污染物。水环境是汞重要的汇,也是汞甲基化和生物累积最重要的场所。作为最重要的初级生产者之一,附着生物广泛存在于湖泊、湿地、溪流等水环境中。相较于底泥和水柱,附着生物具有增强的汞甲基化潜势,是水环境中甲基汞的重要来源以及汞进入食物链的关键途经。附着生物具有多层次的微生物结构及功能复杂性,不同物种间的相互作用使其内部具有明显的氧化还原梯度,形成有利于汞甲基化的缺氧微环境。一方面,附着生物中的藻类和细菌可从周围水体中富集无机汞,为汞甲基化提供充足的底物。另一方面,附着生物中富含多种藻类、细菌等的代谢分泌物,其官能团(如巯基)可调控无机汞的赋存形态并增强其生物有效性。另外,不同微生物之间的代谢物共享可增强汞甲基化细菌的丰度和代谢活性,从而促进甲基汞的生成。附着生物中汞甲基化机制及生物累积的研究可为深入理解水环境中甲基汞的来源及归趋,准确评估汞污染与环境风险提供科学依据与数据支持。

Mercury(Hg)is an important global pollutant.The aquatic environment is an important sink of mercury and the most important site for methylation and bioaccumulation.As one of the most important primary producers,periphyton is widely present in lakes,wetlands,streams,and other aquatic environments.Compared to water columns,periphyton has enhanced mercury methylation potential,which is an important source of methylmercury in aquatic environments and a key pathway for mercury entering into food chains.Periphyton has diverse microbial structures and exhibits highly complex functionality.The interactions among different microorganisms result in distinct redox gradients within periphyton,forming an anoxic microenvironment conducive to mercury methylation.On the one hand,algae and bacteria in periphyton can accumulate inorganic Hg(Ⅱ)from the surrounding water,providing sufficient substrate for mercury methylation.On the other hand,periphyton is rich in metabolic secretions from various algae and bacteria,with functional groups(such as thiol groups)that can regulate the speciation of inorganic Hg(II)and enhance its bioavailability.In addition,different microorganisms can share metabolites,which can enhance the abundance and metabolic activity of Hg-methylating bacteria,thus promoting the production of methylmercury.Overall,clarifying the mercury methylation mechanism and bioaccumulation in periphyton contributes to a further understanding of the source and fate of methylmercury in aquatic environments,and provides scientific basis and data support for accurately assessing mercury pollution and environmental risks.