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