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Using thermocline manipulation to remediate mercury-contaminated reservoirs in southwestern Utah

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Using thermocline manipulation to remediate mercury-contaminated reservoirs in southwestern Utah

Using thermocline manipulation to remediate mercury-contaminated reservoirs in southwestern Utah

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Using thermocline manipulation to remediate mercury-contaminated reservoirs in southwestern Utah Using thermocline manipulation to remediate mercury-contaminated reservoirs in southwestern Utah Presentation Transcript

  • Using thermocline manipulation to remediate mercury-contaminated reservoirs in southwestern Utah USGS, Utah/Wisconsin/Arkansas Water Science Centers Utah DNR/DWR Utah DEQ/DWQ Finnish Environment Institute
  • PROBLEM
  • TOPICS ♦Thermocline manipulation in Finland ♦Application to reservoirs in Utah ♦Remediation objectives
  • From Forsius and others, 2006 METHYL Hg PROFILE
  • THERMOCLINE DEPRESSION Pretreatment epilimnion Post-treatment From Forsius and others, 2006 epilimnion Post-treatment hypolimnion
  • EQUIPMENT ♦ Experiment originally designed for climate change ♦ Artificially decrease From Forsius and others, 2006 thermocline volume ♦ Increase depth of oxygen penetration during summer stratification ♦ More amenable to wind erosion Thermocline mixing equipment (MIXOX).
  • MIXOX DEPLOYMENT ♦ Cost is about 2,000 EU ♦ Powered via lake bottom cable from on-shore From Forsius and others, 2006 power source ♦ Platform provides for easy deployment of additional instruments ♦ Powered via wind/solar/hydroelectric at remote reservoir sites Deployment of mixing equipment and surface platform
  • DEPTH BELOW LAKE SURFACE, IN M T, oC DEPRESSION = 2.0 METERS
  • DECREASE IN METHYL Hg (Rask and others, in review) Fish tissue Water (small perch, 70-80 mm) (epilimnion) 0.6 Thermocline pumping X = 0.54 0.4 MeHg, ng/L 0.2 X = 0.16 0.0 Before During/after pumping pumping
  • DECREASE IN METHYL Hg ♦Decreased volume of anoxic Pre-pumping hypolimnion ♦Increased volume of oxic epilimnion Post-pumping ♦Decreased surface area of anoxic sediment ♦Longer ice-free season
  • POTENTIAL APPLICATION TO SMALL RESERVOIRS IN UTAH
  • NEWCASTLE RESERVOIR Water/sediment ♦ Reservoir dam sampling site completed in 1956 ♦ Small reservoir (66 hectares) ♦ Mean depth = 7.2 meters ♦ Water and sediment sampled during July 2007 ♦ Trout/wipers accumulating high Hg levels in 3 months
  • NEWCASTLE BIOTA
  • DEPTH BELOW WATER SURFACE, IN METERS THERMOCLINE 0 0.2 ng/L 2 [1.45 ng/L] Explanation 4 CH3Hg 6 Hg(inorg) 8 2.5 ng/L [HgTot] 10 whole water 14 16 18 20 22 o WATER TEMPERATURE, C [2.91 ng/L]
  • HISTORIC MERCURY DEPOSITION RATES 2010 Dry mass (g/cm2) * Hg conc. (μg/g) YEAR OF SEDIMENT DEPOSITION 2000 deposition period (yrs) 1990 1980 Spillway raised 1970 Dam 1960 completion 1950 1940 1930 0.00 0.01 0.02 0.03 0.04 2 Sediment core, Newcastle Hg DEPOSITION (UG/CM /YR) Reservoir, Utah
  • NEWCASTLE REMEDIATION OBJECTIVES 1. Calibrate a hydrodynamic model to simulate the naturally induced thermal stratification in Newcastle Reservoir over an annual cycle 2. Utilize the calibrated hydrodynamic model to determine the optimal location(s) and pumping rates needed to depress the thermocline elevation by 1 to 2 meters 3. Utilize results from objective 2 to design a field experiment to depress the thermocline in the experimental reservoir 4. Utilize pre-pumping and pumping data to determine if the thermocline manipulation has resulted in a measurable decrease in mercury concentration in water, sediment, and biota
  • NEWCASTLE REMEDIATION YR 1 TASKS/SCHEDULE ♦ Baseline Hg data ♦ Determine if pumping will work National Park Service QW sampling boat, Lake Powell, Utah
  • NEWCASTLE REMEDIATION YR 2 TASKS/SCHEDULE ♦ Conduct pumping experiment ♦ Model observed pumping results Limnology profiling, Lake Powell, Utah
  • NEWCASTLE REMEDIATION YR 3 TASKS/SCHEDULE ♦ Continue field experiment/modeling ♦ Decide if results warrant implementation Sediment coring platform, Newcastle Reservoir, Utah
  • Hg IN UTAH RESERVOIRS ♦ Many small reservoirs with fish advisories for Hg ♦ Cost effective ($4,000/pump to remediate a fishery) ♦ Baseline (pre-treatment) fish data already collected ♦ Alternative remediation options??