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Warming increases methylmercury production in an Arctic soil
Ziming Yang1, Wei Fang2, Xia Lu1
1Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
Environmental Pollution (Barking, Essex : 1987)
|May 2, 2016
Summary
Arctic permafrost thaw significantly increases methylmercury (MeHg) production, posing risks to ecosystems and human health. Warmer temperatures and available soil organic carbon (SOC) fuel MeHg biosynthesis, with potential for a tenfold increase.
Area of Science:
- Environmental Science
- Geochemistry
- Microbiology
Background:
- Arctic permafrost thaw releases soil organic carbon (SOC) and impacts mercury cycling.
- Methylmercury (MeHg) bioaccumulation poses risks to Arctic wildlife and humans.
- The link between SOC degradation and MeHg production during permafrost thaw is poorly understood.
Purpose of the Study:
- To investigate the effect of warming on MeHg production in Arctic soils.
- To understand the relationship between SOC availability and MeHg biosynthesis.
- To assess the potential impact of permafrost thaw on mercury methylation.
Main Methods:
- An 8-month anoxic incubation experiment was conducted on Arctic soil.
- MeHg production was measured at two temperatures: -2°C and 8°C.
- The role of labile SOC, mercury availability, and co-produced substances (methane, ferrous ions) were analyzed.
Main Results:
- Net MeHg production increased over tenfold at 8°C compared to -2°C in both soil layers.
- Labile SOC, such as reducing sugars and ethanol, significantly fueled initial MeHg biosynthesis.
- Newly added mercury was methylated more readily than existing soil mercury.
- Mercury methylation correlated positively with methane and ferrous ion production.
Conclusions:
- Climate warming and permafrost thaw can enhance MeHg production by an order of magnitude.
- SOC availability and mercury speciation influence MeHg production rates.
- Increased MeHg levels in Arctic food webs are a potential consequence of permafrost thaw.
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