1 / 48

Fish Mercury Impairment in California Reservoirs: Historic Mines and Other Factors

Fish Mercury Impairment in California Reservoirs: Historic Mines and Other Factors. EPA Region 9 State-of-the-Science Workshop on Mercury Remediation in Aquatic Environments September 26, 2013 California Water Boards Multi-Region Team

allene
Télécharger la présentation

Fish Mercury Impairment in California Reservoirs: Historic Mines and Other Factors

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Fish Mercury Impairment in California Reservoirs: Historic Mines and Other Factors EPA Region 9 State-of-the-Science Workshop on Mercury Remediation in Aquatic Environments September 26, 2013 California Water Boards Multi-Region Team Michelle Wood, Carrie Austin, Steve Louie & many others

  2. Outline • Introduction to Statewide Mercury Control Program for Reservoirs • Quick overview of: • California reservoirs fish MeHg impairment • Linkage between fish MeHg bioaccumulation, sources, and other factors • Mercury sources and where they occur • Where might mine remediation enable measurable and timely fish mercury reductions? • WANTED: Your Feedback!

  3. Outline total mercury (Hg) inorganic mercury • Introduction to Statewide Mercury Control Program for Reservoirs • Quick overview of: • California reservoirs fish MeHg impairment • Linkage between fish MeHg bioaccumulation, sources, and other factors • Mercury sources and where they occur • Where might mine remediation enable measurable and timely fish mercury reductions? monomethylmercury MeHg

  4. Statewide Mercury Control Program for Reservoirs Goal: Quickly, measurably reduce fish MeHg • Website with fact sheets & updates www.waterboards.ca.gov/water_issues/programs/mercury • Sign up for email notices at: www.waterboards.ca.gov/resources/ email_subscriptions/swrcb_subscribe.shtml#quality

  5. Fish MeHg Levels • 74 CWA 303(d) listed reservoirs • another ~70+ soon to be listed • Rainbow trout have low MeHg • But so do black bass! [green boxes] Red and orangeindicatefish MeHg exceeds draft target of0.2 mg/kg High elevationSierra Nevada California Pacific Ocean

  6. Fish MeHg Levels • 74 CWA 303(d) listed reservoirs • another ~70+ soon to be listed • Fish were collected from about 350 lakes and reservoirs • ~50% impaired<typical for U.S.> • There are >1,000 reservoirs in CA Red and orangeindicatefish MeHg exceeds draft target of0.2 mg/kg California Control program might need to address ~500 reservoirs Pacific Ocean

  7. It’s a complicated story…

  8. It’s a complicated story… MultipleFactors upstream mines & high sedHg, low fish MeHg low sedHg, high fish MeHg variability

  9. Model Equation LN [Fish methylmercury] = 0.563 *[aqueous total Hg] +0.338 *[aqueous MeHg] /[chlorophyll-a]+0.394 *(annual water level fluctuation)– 0.912 R2= 0.83 Adjusted R2 = 0.81 Predicted R2 = 0.72n = 26 reservoirs, P < 0.001 MeHg 3 factors are equally important!

  10. Multiple factors →Multiple possible tools (a) Source control: Reduce Hg sources to reduce MeHg production in reservoirs Today’s focus: mine waste remediation

  11. Some reservoirs are in naturally Hg-enriched areas

  12. Mercury & Gold Mines 74 303(d)-Listed reservoir watershed boundaries indicated by black outline Hg Mines Au Mines

  13. Reservoir fish MeHg compared to modeled 2001 atmospheric Hg deposition rate At least 1 recorded upstream gold or mercury mine Reservoirs with no record of upstream gold or mercury mines; 60 have fish MeHg > target • Can have high fish MeHg but low atm dep and no mines • Can have low fish MeHg but very high atm Hg dep • Very highest fish MeHg associated with extensive Hg mining MultipleFactors

  14. Key Question: Where can mine waste remediation make quick reductions in reservoir fish MeHg? (a) Source control: Reduce Hg sources to reduce MeHg production in reservoirs Program Goal: Quickly & measurably reduce fish MeHg

  15. Desk-top [GIS-based] analysis: Mine factors considered • High reservoir sediment Hg compared to background • indicates substantial mine contribution • Mine sites localized to a relatively small watershed area • indicates highly contaminated soils likely not dispersed throughout watershed • Mines near reservoirs (e.g., within 10 to 20 km) • likely do not have many miles of creek channels filled with waste that can be difficult to remediate

  16. Initial desk-top analysis results: • 53 of the 74 Hg-impaired reservoirs have at least one recorded upstream mine or prospect • Of these 53: only 3 “probably” and 2 “maybe” reservoirs where mine waste remediation expected to make timely and measurable improvements

  17. A comparison of two neighbors…Part 1

  18. A comparison of two neighbors…Part 2 Linkage Model = TotHg sources + aqMeHg / Chlor-a + water level fluctuation MeHg Halfwayto target

  19. A comparison of two neighbors…Part 2 Halfwayto target Not controllable

  20. A comparison of two neighbors…Part 2 Linkage Model = TotHg sources + aqMeHg / Chlor-a + water level fluctuation MeHg Halfwayto target Not controllable

  21. A comparison of two neighbors…Part 2 Nacimiento ≈MeHg machine! Likely controllable aqMeHg/Chlor-a ratio >5x higher inNacimiento Halfwayto target Likely not controllable Not controllable

  22. Key Question: Where can mine waste remediation make timely reductions in reservoir fish MeHg? We evaluated: • High reservoir sediment Hg compared to background • Localized mine sites • Mines near reservoirs • What other factors can we consider? • mine processes • mine productivity • others??? We need realistic expectationsof where quick improvements are possible from mine waste remediation

  23. Let there be no doubt…We are still advocating mine waste remediation as a tool to reduce fish MeHg… And we are looking forward to coordinating with stakeholders to explore ways to prioritize specific sites within a watershed, e.g.… • Proximity and erosion of waste to surface water: • High threat - visual evidence or high potential of wastes eroding into surface waters • Medium threat - wastes near waters but no visual evidence of erosion • Low threat - wastes located far from waters and no visible evidence of erosion • Level of Hg contamination: • Historical mine processes and productivity • Waste pile and portal discharges: Hg concentrations and volumes • Hg concentrations in downstream water and sediment • Site accessibility Future Meetings

  24. Find Out More, Stay in Touch • Website with fact sheets & updates www.waterboards.ca.gov/water_issues/programs/mercury • Sign up for email notices at: www.waterboards.ca.gov/resources/ email_subscriptions/swrcb_subscribe.shtml#quality • Hand out • Project goals & contact info • Discussion questions from this presentation

  25. Key Question: Where can mine waste remediation make timely reductions in reservoir fish MeHg? We evaluated: • High reservoir sediment Hg compared to background • Localized mine sites • Mines near reservoirs • What other factors can we consider? • mine processes • mine productivity • others??? We need realistic expectationsof where quick improvements are possible from mine waste remediation

  26. Extra Slides for Possible Questions

  27. We have reasons to be hopeful… Source: Teck Cominco-Azimuth 2008 (Figure 4.6-1) Source: Kirchner et al. 2011 (Figure 3a) Fish MeHg Conc. (mg/kg) • Logscale • Lake Pinchi Mercury Mine, BC • Some waste capping & erosion control since 1975 mine closure; additional remediation planned • Initial dramatic fish MeHg reduction, then modest reductions • Coring indicate slow burial process – no large tributaries to provide significantly cleaner sediment • Gambonini Mercury Mine • Largest Hg pollution source to Walker Creek & Tomales Bay • Erosion control alone – no capping! >90% Hg load reductions & >50% sediment load reductions • But we don’t yet have fish MeHg data

  28. Prioritizing where to start additional mine remediation within a watershed • Proximity and erosion of waste to surface water: • High threat - visual evidence or high potential of wastes eroding into surface waters • Medium threat - wastes near waters but no visual evidence of erosion • Low threat - wastes located far from waters and no visible evidence of erosion • Level of Hg contamination: • Historical mine processes and productivity • Waste pile and portal discharges: Hg concentrations and volumes • Hg concentrations in downstream water and sediment • Site accessibility

  29. Next steps • Learn from what we hear today and enhance our evaluation! • Have follow-up meetings with workshop participants and other interested stakeholders during the next couple months to continue to enhance the evaluation • Scientific peer review of draft technical report in 2014

  30. Nacimiento Reservoir Sediment THg

  31. Nacimiento Reservoir Fish THg(ATSDR 2007, Figure 5)

  32. Sources and Methylation of Mercury

  33. Building a Reservoir Before After

  34. LinkageAnalysis • >30 reservoir and watershed variables • This is just one analysis example…

  35. Reservoirs: Multiple factorscontribute to impairment Comes down to 3 factors: Total Hg = (a) sources MeHg/Chl-a = (b) methylation / (c) bioaccumulation Reservoir fluctuation = (b) methylation / (c) bioaccumulation one size fits all Several tools: Select right tool(s) for each reservoir

  36. Potential Solutions toReduce Fish Mercury Source control Water chemistry(decrease methylation) Fisheries management

  37. Multiple factors → Multiple possible tools (b) Water chemistry (reduce methylation):Studies & pilot tests to reduce in-reservoir MeHg production: - Reduce anoxia with artificial circulation or oxygenation, or adjust redox potential by adding nitrate - If low pH, increase pH by adding lime or reducing air emissions (NOx, SOx, etc.) that produce acid rain

  38. Multiple factors → Multiple possible tools (c) Fisheries & food web management: Studies & pilot tests to manage food web to reduce MeHg bioaccumulation -Add nutrients to oligotrophic reservoirs to increase productivity at food web base - Manipulate food web, e.g., intensive fishing, to increase growth rate of remaining fish - Restore native anadromous fisheries (e.g., salmon & steelhead trout) - Change stocking to increase numbers of less predatory fish

  39. Reservoir fish MeHg compared to modeled 2001 atmospheric Hg deposition rate At least 1 recorded upstream gold or mercury mine No record of upstream gold or mercury mines • Can have high fish MeHg but low atm dep and no mines • Can have low fish MeHg but very high atm Hg dep • Very highest fish MeHg associated with extensive mining MultipleFactors

  40. USEPA’s REMSAD 2001 model output for atmospheric Hg deposition throughout the U.S. • Overall, atm dep rates low in CA • Some limited areas rival atm dep rates in eastern U.S. Source: USEPA 2008a (Figure 6-3c)

  41. USEPA’s REMSAD 2001: % of atmospheric Hg deposition from sources CA regulators cannot regulate • Several reservoirs in areas with 30 to 80% of atm dep from CA industrial sources (blue arrows) YELLOW-RED: >90%natural + international industrial DARKEST GREEN: >60% CA industrial • Statewide: ~10% : CA industrial sources ~60% : International industrial sources ~30% : Natural sources

  42. Sources of Hg in atmospheric deposition per USEPA’s REMSAD model output for 2001 & literature review

  43. Reservoir fish MeHg and upstream mines No mines, high fish MeHg • Almost half of reservoirs (~150) exceed draft target • More than a third of those (~60) do not have upstream mine sites Reservoir or lake with no upstream mines No mines, low fish MeHg No mines, high fish MeHg

  44. Reservoirs with very high fish MeHg ~40% ~60%

  45. Mine waste remediation is a useful tool, but benefits may take a while to observe in many downstream reservoirs • Many reservoirs have a high density of mine sites over much of their watersheds, some with watershed sizes bigger than many countries… • Need to consider mine waste already in creek and river channels that may be difficult to remediate MRDS gold mine features upstream of 303(d) Listed Hg-impaired reservoirs in the Feather, Yuba, & Bear Rivers’ watersheds

  46. Mine waste remediation is a useful tool, but benefits may take a while to observe in many downstream reservoirs • Many reservoirs have a high density of mine sites over much of their watersheds,some with watershed sizes bigger than many countries… • Need to consider mine waste already in creek and river channels • Need to consider potential for widespread elevated soil THg from past mining activities’ air emissions Profile of Hg concentration in soil impacted by release of particulate Hg and vapor from Hg mines in the New Idria Mercury District, California [Source: Rytuba 2002, Figure 2]

More Related