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North Carolina Eastern Regional Mercury Study: Results

North Carolina Eastern Regional Mercury Study: Results. Michelle Woolfolk NC Division of Water Quality Presented April 19, 2004 at the CSSA Meeting. NC Eastern Regional Mercury Study. Funded by USEPA grant (104(b)(3)) Goals

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North Carolina Eastern Regional Mercury Study: Results

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  1. North Carolina Eastern Regional Mercury Study: Results Michelle Woolfolk NC Division of Water Quality Presented April 19, 2004 at the CSSA Meeting

  2. NC Eastern Regional Mercury Study • Funded by USEPA grant (104(b)(3)) • Goals • Evaluate levels of ambient mercury in surface water systems using low level techniques (Method 1631) • Estimate site-specific total mercury:methyl mercury translators to evaluate water quality criteria • Estimate site-specific water to fish bioaccumulation factors • Evaluate potential mercury loads from WWTPs • Referred to hereafter as the ERMS

  3. Ambient Surface Water Total Hg Standard exceeded in 11 % of samples. Goal 1: Ambient mercury levels

  4. Ambient Surface Water Total MeHg Goal 1: Ambient mercury levels

  5. Ambient sediment Total Hg Goal 1: Ambient mercury levels

  6. Ambient sediment Total MeHg Goal 1: Ambient mercury levels

  7. Ambient Hg residue: piscivorous fish Black crappie Goal 1: Ambient mercury levels

  8. Ambient Hg residue: Omnivores and Insectivores White catfish Spotted sucker

  9. Bioaccumulation factors • Bioaccumulation is the uptake and retention of a chemical by a living organism as a result of either intake of food, drinking water, air or direct contact. (EPA 1994b) • A bioaccumulation factor is defined as : BAF = Residue C(d) where Residue = concentration in wet tissue, mg/kg C(d) = concentration of chemical dissolved in H2O, mg/L Goal 3: Bioaccumulation

  10. Bioaccumulation factors, cont. • Can be species specific, size specific, or trophic level specific • Species specific: e.g., largemouth bass, black crappie, bluegill sunfish, etc. • Size specific: e.g., largemouth bass of length 40 cm • Trophic level specific: e.g., all of trophic level 3 Goal 3: Bioaccumulation

  11. Largemouth bass bioaccumulation • One of three species with a regional advisory by DHHS • Caught and analyzed at every site in ERMS (makes site-to-site comparison possible) • Calculate BAFs to all fish caught at a site and to a “normalized” 40-cm bass • Allow variability in exposure concentration Goal 3: Bioaccumulation

  12. Largemouth bass BAFs Goal 3: Bioaccumulation

  13. 40-cm Largemouth bass BAFs Goal 3: Bioaccumulation

  14. What is the significance of BAFs? • We use the BAFs to calculate the allowable water concentrations of MeHg(d) and ultimately Hg(t). • Required to implement the AWQC for methylmercury Goal 3: Bioaccumulation

  15. Target water column levels • Evaluate human health endpoint, not wildlife • Only evaluate to DHHS criteria • Site-specific water column translators (i.e., MeHg(d)/MeHg(t) and MeHg(t)/Hg(t)) [less confidence in relationships between MeHg(d) and Hg(t)] Goal 3a: Target water levels

  16. Target water column levels Goal 3a: Target water levels

  17. Target water column levels, cont. Goal 3a: Target water levels

  18. And now for the big picture…

  19. Photo-toon by R. Johnson

  20. Questions? Michelle Woolfolk Div. of Water Quality, Modeling Unit (919) 733-5083 ext. 505 michelle.woolfolk@ncmail.net Connie Brower Div. Of Water Quality, Standards Unit (919) 733-5083 ext. 572 connie.brower@ncmail.net

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