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Robert Hudson and Brian Vermillion , University of Illinois Thomas Simon , Indiana University

Anthropogenic and biogeochemical influences on the distribution of methylmercury in fish, surface waters, and sediments of lacustrine wetlands in the Grand Calumet Region (Indiana, USA). Robert Hudson and Brian Vermillion , University of Illinois Thomas Simon , Indiana University

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Robert Hudson and Brian Vermillion , University of Illinois Thomas Simon , Indiana University

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  1. Anthropogenic and biogeochemical influences on the distribution of methylmercury infish, surface waters, and sediments of lacustrine wetlands in the Grand CalumetRegion (Indiana, USA) Robert Hudson and Brian Vermillion, University of Illinois Thomas Simon, Indiana University Joy Marburger, USPS-Indiana Dunes Gabriel Filipelli, IUPUI

  2. Research Objectives • Develop new, accurate methods for methylmercury analysis that permit environmental samples to be analyzed at lower cost. • Field test methods in INDU/ Grand Calumet region in order to: • Aid in understanding the Hg pollution problems in Grand Calumet AOC, • Help establish validity of methods.

  3. Speciation Analysis by Hg2+/MeHg+-Thiourea Complex Ion Chromatography New method for MeHg analysis developed at UIUC employs mercury-thiourea complex ion chromatography with post-column oxidation, cold vapor generation and Hg detection by atomic fluorescence spectrometry. The same detector is used as for standard methods of THg, MeHg analysis, but is based on a new chemistry for separating MeHg and HgII. Shade and Hudson (ES&T 2005)

  4. Sample Preparation Methods

  5. Calumet Region of Northwestern Indiana Lake Michigan • Nine lacustrine wetlands surveyed four times in2006-2007. • Over 30 wetlands surveyed in July 2006.

  6. Seasonal Dynamics

  7. Strong pH-Dependence of Dissolved MeHg in Grand Calumet Wetlands 3 separate samples collected per site per event.

  8. MeHg: DOC Ratios Highest During Summertime in Calumet Wetlands

  9. Spatial Survey • Stratified (by size) random design. • Samples collected along 3-5 “transects” per wetland. • One sample per transect analyzed (typically 3 per wetland).

  10. Hg in Sediments All samples

  11. Porewater Hg Species All samples

  12. July 2006 Spatial Survey Geometric Means for Each Site

  13. Geochemical Factor Analysis N=27

  14. Organisms Analyzed for MeHg and Total Hg • No sample exceeded 300 ppb. • MeHg was 83-99% of total Hg.

  15. National Descriptive Model of Hg in Fish (Wente/USGS) ln(Cijk+ 1) = k× ln(LENGTHijk +1) + j +ijk • i=specimen index • j=sampling site/event index • k=species/cut index • Approximation: • Where possible, use published k. • Estimate k for mud minnow, crayfish, golden shiner. • Derive site-specific factor (j ) from this dataset.

  16. NDMMF Predictions

  17. Factor Analysis - Biota

  18. Summary • The new MeHg analysis methods were successfully employed to analyzed a large number of samples. • Geochemical relationships between MeHg and other variables were consistent with observations made in other systems using conventional methods of analysis. • Dissolved MeHg was controlled by organic matter in water and sediments. • Hg in biota from the surveyed wetlands never exceeded 300 ppb. • NDMMF-predicted values for standard perch did exceed 300 ppb at 2(3) sites.

  19. Acknowledgements • Sea Grant: Funding. • NPS: Access to facilities and sites. • IDEM: Access to sites.

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