Methylmercury Biogeochemistry in Freshwater Ecosystems: A Review Focusing on DOM and Photodemethylation

Mercury contamination is a growing concern for freshwater food webs in ecosystems without point sources of mercury. Methylmercury (MeHg) is of particular concern, as this is the form of mercury that crosses the blood–brain barrier and is neurotoxic to organisms. Wetlands and benthic sediments have h...

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Bibliographic Details
Published in:Bulletin of environmental contamination and toxicology 2018, Vol.100 (1), p.14-25
Main Authors: Klapstein, Sara J., O’Driscoll, Nelson J.
Format: Article
Language:English
Subjects:
Anaerobic bacteria
Aquatic ecosystems
Aquatic Pollution
Bacteria
Bioavailability
Biodegradation
Biogeochemistry
Brain
Contamination
Dimethylmercury
Dissolved organic matter
Earth and Environmental Science
Ecotoxicology
Environment
Environmental Chemistry
Environmental Health
Focused Review
Food Chain
Food chains
Food contamination
Food webs
Fresh water
Freshwater ecosystems
Freshwater lakes
Humic Substances
Lakes - chemistry
Mercury
Mercury (metal)
Mercury - analysis
Methylation
Methylmercury
Methylmercury Compounds - analysis
Methylmercury Compounds - chemistry
Neurotoxicity
pH effects
Photochemical Processes
Photochemistry
Point sources
Pollution
Sediments
Soil Science & Conservation
Waste Water Technology
Water Management
Water Pollutants, Chemical - analysis
Water Pollutants, Chemical - chemistry
Water Pollution Control
Wetlands
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Summary:Mercury contamination is a growing concern for freshwater food webs in ecosystems without point sources of mercury. Methylmercury (MeHg) is of particular concern, as this is the form of mercury that crosses the blood–brain barrier and is neurotoxic to organisms. Wetlands and benthic sediments have high organic content and low oxygen availability. Anaerobic bacteria drive the metabolic function in these ecosystems and subsequently can methylate mercury. The bioavailability of MeHg is controlled by physicochemical characteristics such as pH, binding affinities, and dissolved organic matter (DOM). Similarly, photodemethylation is influenced by similar characteristics and thereby the two processes should be studied in tandem. The degradation of MeHg through photochemistry is an effective destruction mechanism in freshwater lakes. This review will highlight the uncertainties and known effects of DOM on subsequent photoreactions that lead to the occurrence of mercury photodemethylation and reduction in mercury bioavailability in freshwater ecosystems.
ISSN:0007-4861
1432-0800
DOI:10.1007/s00128-017-2236-x