Joel Creswell - Factors controlling temporal and spatial distribution of total mercury and methylmercury in hyporheic sediments of the Allequash Creek wetland, northern Wisconsin

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  Publication Details (including relevant citation   information):

  Creswell, J. E.; Kerr, S. C.; Meyer, M. H.;   Babiarz, C. L.; Shafer, M. M.; Armstrong, D. E.; Roden, E. E.   2008. Temporal and spatial distribution of total mercury and   methylmercury in hyporheic sediments of the Allequash Creek   wetland. Journal of Geophysical Research -   Biogeosciences 113(G00C02). doi:   10.1029/2008JG000742.


  Hyporheic pore water samples were collected from two sites within   the Allequash

  Creek wetland, in Vilas County, northern Wisconsin, from August   2003 to October 2004.

  Samples were collected simultaneously at the surface and at 2, 5,   7, 10, and 15 cm below

  the sediment-water interface. Concentration ranges were 3.7 to 58   pM for inorganic

  mercury, <0.5 to 16 pM for methylmercury, 3.02 to 152 mM and   0.38 to 96.6 mM for

  oxidized and reduced iron, respectively, 1.28 to 48.2 mM and<   0.05 to 9.76 mM for

  oxidized and reduced sulfur, respectively, and 109 to 689 mM for   dissolved organic

  carbon. These concentrations are typical of anoxic environments   such as wetlands and

  lake sediments. These data were used to gain a better   understanding of the processes

  controlling spatial and temporal variability of inorganic mercury   and methylmercury.

  Findings show that conditions conducive to mercury methylation   exist in the hyporheic

  zone, especially in late summer, when accumulation of reduced   iron and sulfide are

  indicative of microbial iron and sulfate reduction. Methylmercury   concentrations also

  peak in late summer, with the highest concentrations appearing 2   to 10 cm below the

  sediment-water interface. While there is a general covariance of   total mercury and

  methylmercury over the depth profile, poor correlation was   observed over time,

  highlighting the dynamic nature of hyporheic zone conditions and   suggesting changes in

  mercury speciation and partitioning.

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