Use of Iron to Control of Methylmercury
Formation in Wetlands
Wetlands provide a variety of ecosystem services including
improvement of water quality, protection of fisheries and flood
control. Currently there are numerous efforts underway to
restore wetlands that have been lost to development.
Unfortunately, many of the areas targeted for restoration are
located in watersheds where fish and waterfowl contain elevated levels
of mercury. Because methylmercury (i.e., the toxic form of
mercury that accumulates in food webs) is formed readily in wetland
sediments, restoration efforts may have the unintended
consequence of exacerbating metrcury problems.
In our previous research we showed that addition of iron to wetland
sediments can decrease the rate of formation of methylmercury (Mehrotra
et al. 2003, Mehrotra and Sedlak 2005) by decreasing theconcentration
of dissolved bisulfide in the sediment pore water (Figure 1).
Figure
1. Effect of adding iron to methylmercury concentrations
(top) and porewater sulfide (bottom).
Our previous experiments were conducted under well-controlled
laboratory conditions using either pure cultures of sulfate-reducing
bacteria or wetland sediments incubated in closed containers.
In our current research project, we are exploring the effect
of iron addition on mercury methylation under conditions closer to
those encountered in the field using microcosms with wetlands plants
and a simulated tidal cycle. Preliminary results indicate
that iron addition decreases methylercury production and that the
effect of iron addition persists for at least three months.
Ongoing research is targeted at determining the dose of iron
needed for effective methylmercury control with the objective of
conducting pilot-scale experiments at field sites where wetland
restoration in planned in the San Francisco Bay region.
Figure
2. Doctoral student Patrick Ulrich supervises the
collection of wetland sediments for microcosm experiments.
For more information see:
- Mehrotra A.S., Horne A.J. and Sedlak D.L.
(2003) Inhibition of net mercury methylation by Desulfobulbus
propionicus cultures: implications for engineered wetlands. Environ. Sci. Technol. 37,
3018-3023. DOI:
10.1021/es0262838
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The Fate of
Hormones in the Aquatic Environment
Use of Iron to Control Methylmercury Formation in Wetland Sediments
Oxidation of
Contaminants by Iron Nanoparticles in the Presence of Oxygen
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