Hello, everyone. The production of methlymercury (MeHg) was primarily conducted by anaerobic microorganisms including sulfate- and iron-reducing bacteria, methanogens, and other syntrophs. Thus, the amount of inorganic mercury (Hg(II)) that is bioavailable to these organisms is an important factor for controlling Hg(II) methylation. Due to the complexity of Hg speciation in sediments, quantification of the bioavailable fraction remains a great challenge. So, which method would be potential strategies ? the concentrations of Hg(II) in pore water ? the contents of low-molecular-weight (LMW) thiols (e.g. cysteine, thioglycolic acid) which could affect its bioavailability and thus MeHg production? passive sampling like diffusive gradients in thin films (DGT)? a selective model organism using to stimulate the Hg uptake process into methylating microbes?
I don't know the performance difference between those methods. So if anyone can share your opinion or scientific story, I'd be most grateful.
You may be interested in publications from US National Mercury Lab. Coastal areas dominated by wetlands and black, tannic water streams are susceptible to noticeable bioaccumulation issues. We found difficulty in limited sampling of sediments in finding reliable concentrations. We sampled the fatty tissues of predatory fish species with better success without basic, brief water quality report on the Francis Marion National Forest, sediment was less reliable and often low concentration. The National Mercury lab has found high concentrations in mosquito fish. Not all aquatic sediments are anaerobic, so that may add complexity. I talked to Dr. Krabbenhoft (spelling) the US National Mercury Lab several times. You might try contacting him directly for his opinion on your hypothesis. https://wi.water.usgs.gov/mercury-lab/research/index.html
The potential strategies for predicting or quantifying the amount of bioavailable ( Hg(II ) in water and sediment include measurements of the " dissolved" or filter-passing phase ( typically 0.2 or 0.45 microns nominal pore size ) or the solid - aqueous Hg partition coefficient where the aqueous fraction is defined by this filter - passing phase. Despite this widely employed approach, the filter - passing Hg concentraion rarely correlate with Hg methylation rates or MeHg concentration. Another approach is to infer Hg speciation using chemical equilibrium speciation models and assume the subset of dissolved species are available. For details consult Environmental Science and Tecchnology. Vol. 52 issue 15: pp. 8510 - 8520. http://dol.org/10121/acs.est.8b02515
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