The Relationship Between Mercury Loading AndFish Mercury Concentrations:Some Modeling And Field PerspectivesFishHgHg LoadReed HarrisTetra Tech Inc.January 4, 2005
Lab experiment showing linear effect of HgII load onmethylmercury production… to a point.. What about real world?
Effect of Hg deposition on fish Hg• Some datasets suggest a link• Difficult to isolate effects of Hg loading
(Mercury Experiment To Assess AtmosphericLoading in Canada and the US)
Principal Investigators:Canadian DFO Freshwater InstituteKen Beaty, Paul Blanchfield,Drew Bodaly, Mike Paterson,Cheryl PodemskiAcademy of Natural SciencesCynthia GilmourR&K ResearchJohn Rudd, Carol KellyTetra Tech Inc. Reed HarrisTrent Univ. Holger HintelmannUSGS David KrabbenhoftUS DOE Steve LindbergU. Alberta Vince St. LouisU. MarylandAndrew Heyes, Robert MasonU. Montreal Marc AmyotU. Toronto Brian BranfireunU. WisconsinJames Hurley, Christopher Babiarz
What is METAALICUS?• A loading experiment: : Mercury is being added to alake and its surrounding watershed.Measure Different Contributions to Fish Hg200Hg202Hg198Hg(Upland)(Lake)(Wetland)
How much is wet Hg deposition being increased?35302520151050IsotopeBackgroundELA -CurrentN.WisconsinDorset, Ont.FloridaEvergladesSwedenWest Coast(1987-89)ELA -Experimentug/m2/yr
What about effects of point source Hg loads?
• 10 tonnes ofHg releasedtoWabigoonRiver from1962-69Clay Lake~ 80 kmdownstreamRelease fromchlor-alkalifacility
Watershed Area = 440 km 2Elevation: 1,155 m — sea levelMean Annual Precipitation: 0.4 – 1.2 mGuadalupe River FlowDry season: 0.03 – 0.5 m 3 sec -1Wet season: 3.5 – 297 m 3 sec -1
What are the “MCM” Models?• Models to predict the behaviour andbioaccumulation of mercury in lakes orwetlands← End point of concern is typically fish Hg• Process, mass balance approach tofollow important forms of Hg• Developed by EPRI, Wisconsin DNR,EPA, Florida DEP, South Florida WaterManagement District
MCM Applications514Devil’s LakePilot TMDLTMDLMcPheeReserviorTMDL23EvergladesPilot TMDL
Initial model development based onintensive studies in Wisconsin1) Mercury in Temperate LakesStudy (MTL)- Original model developed andapplied to 7 Wisconsin SeepageLakes2) Mercury Accumulation Pathwaysand Processes (MAPP)- Extension of model to wider set of21 Wisconsin seepage lakesPredicted Fish Hg (ug/gwet)R-MCM Predicted vs Observed Hg in YellowPerch for 21 Wisconsin Lakes0.30.250.20.150.10.050r-squared = 0.65to 0.80SpruceLake0 0.1 0.2 0.3Observed Fish Hg (ug/g wet)1:1MAPP, age 3MTL, age 11988-95
Pilot Hg TMDL for Florida Everglades:Overview of Hg Cycling in E-MCMEverglades MCM (E-MCM)• Lake model adapted forEverglades marshes• Closely tied to ACME andother R&D programs• Model applied to severalsites ranging from low tohigh fish Hg• E-MCM used in pilot HgTMDL at hot spotHg (ug/g wet muscle)54.543.532.521.510.500 20 40 60E-MCM12/3/969/17/9710/21/971/20/98length (cm)11/4/98Modeled Hg in largemouth bass in WCA 3A-15(calibration is better description than prediction)
Estimate Hg loads to system and model what happens underdifferent loading regimes..
Calibrate Hg concentrations in fish of interest..5Hg (ug/g wet muscle)4.543.532.521.51E-MCM12/3/969/17/9710/21/971/20/9811/4/980.500 10 20 30 40 50 60length (cm)Estimated fromw hole bodyFigure 20. Predicted long-term methylmercury concentrations in largemouth bass in WCA 3A-15for calibration with current atmospheric Hg(II) deposition = 35.32 mg/m2/yr. Observations: Langeet al., unpublished data
Make predictions about long term magnitude ofresponse to changes in loading..21.75Fish Hg (ug/g wet muscle)1.51.2510.750.5y = 0.0480x + 0.11000.2500 10 20 30 40Atmospheric Hg(II) deposition (wet and dry, ug/m2/yr)Proportional response E-MCM Predicted Linear fit of E-MCM results
Make predictions about timing of response to changes in loading..21.8Fish Hg (ug/g wet muscle)184.108.40.206.220.127.116.11 10 20 30 40 50 60 70 80 90 100Time After Load Reduction (years)25% Reduction 50% Reduction 75% Reduction 85% ReductionFigure 25. Predicted dynamic response of Hg concentrations inlargemouth bass in WCA 3A-15 following different reductions in Hg(II)deposition.
Aquatic Modeling for Devil’s s Lake, WIPilot Mercury TMDL
Devil’s Lake, WI
Effect of assumed sediment depth on predicted timingof response for Devil’s Lake..1.2Fraction of initial MeHg1.00.80.60.40.23 mm sediments3 cm sediments0.00 20 40 60 80 100Time after 50% load reduction (years)
Handling uncertainty: Monte Carlo approachCount4540353025201510500.05 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95 1.05 1.15 1.25 1.35 1.45 1.55Methylmercury concentration in 5 year old walleye (ug/g wet muscle)middle of intervalCurrent conditions (arithmetic mean = 0.47)Steady state after 50% load reduction (arithmetic mean = 0.26)
Current capability of Hg modelsR&D tool to improve understandingTerrestrialmodelsMarinemodelsRiversAtmosphericLake modelsmodelsFishBioenergetics Model developmentand incorporation ofnew R&D Model calibration Model validationPredictions and mitigation testing
Modeling challenges for Hg TMDLs• Predicting the magnitude of the response:– Are the assumptions resulting in a near-linear response to Hg loading true?– What Hg species are methylated and where?• Predicting the timing of the response:– How big are the pools of Hg involved(new/old Hg, depth of sediments..)– What time lags are imposed by the terrestrial system• Data:– Establishing baselines– Getting models to work with reasonable amount of data.• Uncertainty associated with predictions
River Hg modeling..Peak effect for MeHg may not be at point of release?Dissolved oxygen analogy, but dealing with a sourceinstead of a sink:MeHg inwaterDistance from source