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Fish Mercury Impairment in California Reservoirs:
Historic Mines and Other FactorsEPA Region 9 State-of-the-Science Workshop on
Mercury Remediation in Aquatic Environments
September 26, 2013
California Water BoardsMulti-Region Team
Michelle Wood, Carrie Austin, Steve Louie & many others
•WANTED: Your Feedback!
OutlineIntroduction 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?
•2
total mercury (Hg)inorganic mercuryOutline
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?
•3
monomethylmercuryMeHg
Statewide Mercury Control Program for Reservoirs
Goal: Quickly, measurably reduce fish MeHg
•4
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
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]
•5
Red and orangeorange indicatefish MeHg exceeds
draft target of0.2 mg/kg
Pacific Ocean
California
•
High elevationSierra Nevada
Fish MeHg Levels
74 CWA 303(d) listed reservoirs
another ~70+
soon to be listed
•6
Control program might need to address ~500 reservoirs
Red and orangeorange indicatefish MeHg exceeds
draft target of0.2 mg/kg
Pacific Ocean
California
• Fish were collected from about 350 lakes and reservoirs
• ~50% impaired<typical for U.S.>
• There are >1,000 reservoirs in CA
It’s a complicated story…
•7
It’s a complicated story…
•8
MultipleFactors
low sedHg,high fish MeHg variability
upstream mines & high sedHg, low fish MeHg
3 factors are equally important!
Model Equation
•9
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
Today’s focus: mine waste remediation
Multiple factors → Multiple possible tools
•10
(a)Source control: Reduce Hg sources to reduce MeHg production in reservoirs
Some reservoirs are in naturally Hg-enriched areas
•11
Mercury & Gold Mines
•12
74 303(d)-Listed reservoir watershed boundaries indicated by black outline
Hg Mines Au MinesAu Mines
•13
Reservoir fish MeHg compared to modeled 2001 atmospheric Hg deposition rate
Reservoirs with no record of upstream
gold or mercury mines;
60 have fish MeHg > target
At least 1 recorded upstream gold or mercury mine
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
Key Question: Where can mine waste remediation make quick reductions in reservoir fish MeHg?
•14
Program Goal: Quickly & measurably reduce fish MeHg
(a) Source control: Reduce Hg sources to reduce MeHg production in reservoirs
Desk-top [GIS-based] analysis: Mine factors consideredHigh 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
•15
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
•16
A comparison of two neighbors…Part 1
•17
350 mm Bass MeHg
(mg/kg)
Reservoir sediment
Hg (mg/kg)
Localized mines?
Mine proximity
(km)
REMSAD atm dep
rate (g/km2/yr)
San Antonio 0.24 0.071
prospectna 8.0 (low)
Nacimiento 1.1 0.39 Yes <10-20 8.2 (low)
Halfwayto target
A comparison of two neighbors…Part 2
•18
Likelyfish MeHg reduction
from source control
Watershed soil Hg (mg/kg)
Annual reservoir
water level fluctuation
(feet)
Aqueous MeHg
Geomean [peak] (ng/L)
Chlor-a
(μg/L)
San Antonio minimal 0.04 25 0.04 [0.9] 6.2
Nacimiento ~40% 0.08 48 0.08 [3.7] 2.2
MeHg
Linkage Model
= TotHg sources
+ aqMeHg / Chlor-a
+ water level fluctuation
A comparison of two neighbors…Part 2
•19
Likelyfish MeHg reduction
from source control
Watershed soil Hg (mg/kg)
Reservoir sediment
Hg (mg/kg)
Aqueous MeHg
Geomean [peak] (ng/L)
Chlor-a
(μg/L)
San Antonio minimal 0.04 0.07 0.04 [0.9] 6.2
Nacimiento ~40% 0.08 0.39 0.08 [3.7] 2.2
Halfwayto target
Not controllable
A comparison of two neighbors…Part 2
•20
Likelyfish MeHg reduction
from source control
Watershed soil Hg (mg/kg)
Annual reservoir
water level fluctuation
(feet)
Aqueous MeHg
Geomean [peak] (ng/L)
Chlor-a
(μg/L)
San Antonio minimal 0.04 25 0.04 [0.9] 6.2
Nacimiento ~40% 0.08 48 0.08 [3.7] 2.2
MeHg
Linkage Model
= TotHg sources
+ aqMeHg / Chlor-a
+ water level fluctuation
Halfwayto target
Not controllable
Nacimiento ≈ MeHg machine!
A comparison of two neighbors…Part 2
•21
Likelyfish MeHg reduction
from source control
Watershed soil Hg (mg/kg)
Annual reservoir
water level fluctuation
(feet)
Aqueous MeHg
Geomean [peak] (ng/L)
Chlor-a
(μg/L)
San Antonio minimal 0.04 25 0.04 [0.9] 6.2
Nacimiento ~40% 0.08 48 0.08 [3.7] 2.2
Halfwayto target
aqMeHg/Chlor-a ratio >5x higher inNacimiento
Not controllable
Likely not controllable Likely controllable
We evaluated:High reservoir sediment Hg compared to background
Localized mine sites
Mines near reservoirs
•22
What other factors can we consider?mine processesmine productivityothers???
Key Question: Where can mine waste remediation make timely reductions in reservoir fish MeHg?
We need realistic expectations
of where quick improvements are possible from
mine waste remediation
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 •23
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
•24
We evaluated:High reservoir sediment Hg compared to background
Localized mine sites
Mines near reservoirs
•25
What other factors can we consider?mine processesmine productivityothers???
Key Question: Where can mine waste remediation make timely reductions in reservoir fish MeHg?
We need realistic expectations
of where quick improvements are possible from
mine waste remediation
•26
•27
Extra Slides for Possible Questions
•28
We have reasons to be hopeful…
•29
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
Fis
h M
eH
g C
on
c.
(mg
/kg
)
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
Source: Teck Cominco-Azimuth 2008 (Figure 4.6-1) Source: Kirchner et al. 2011 (Figure 3a)
•Logscale
Prioritizing where to start additional mine remediation within a watershedProximity 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
•30
Next stepsLearn 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
•31
Nacimiento Reservoir Sediment THg
•32
Hubbert 1991 Water Boards 2013
Area General Location[range ci ted in
Rice et a l . 1994]
Site Result
Area Average Site Result
Pebblestone Shut-In 0.01Oak Shores area 0.04Las Tablas Creek Arm 1.5Las Tablas Creek Arm 1.6
East of LTC Arm
Mile 19 (Las Tablas Creek Arm) 0.05-1.2 0.08 0.08 na
Dip Creek shore 0.02Mile 17 (Dip Creek) 0.18Snake Creek Arm; Heritage Ranch 0.08Dip Creek mouth 0.07Snake Creek mouth 0.13
3.09Las Tablas Creek Arm
Rice et al. 1994
na
0.05
Lake Nacimiento Bottom Sediment Total Mercury Data (mg/kg)
0.04-0.16
0.05 to 0.62
0.17-0.99 1.55
0.03
0.10
Upper
Near Dam
•33
Nacimiento Reservoir Fish THg(ATSDR 2007, Figure 5)
•34
Sources and Methylation of Mercury
•35
Before After
LinkageAnalysis
>30 reservoir and watershed variables
This is just one analysis example…
•36
Pearson'sr
Spearman'sRho
[aq MeHg] Geomean / [Chl-a] Geomean 0 0.67 0.70Reservoir Sediment [THg] Geomean 0 0.50 0.47Watershed Soil [THg] Geomean 0 0.40 0.44Reservoir Longitude 5 0.39 0.40Reservoir [Chl-a] Geomean -0.22 0.34 0.27Average Water Level Fluctuation 0 0.33 0.35Watershed Percent Vegetation 3 0.32 0.29[aq MeHg] Geomean -0.5 -0.31 -0.38[aq THg] Geomean 0 0.30 0.25Watershed Percent Open Water 0 -0.27 -0.30Reservoir Dam Height 0.5 0.25 0.34Reservoir Elevation 0.21 -0.22 -0.27Watershed Percent Forests 2 0.22 0.12CA Hg Atm Dep Rate to the Watershed 0 0.19 0.17Watershed Productive Mines per Mile -3.77 -0.17 -0.05Number of Mines in Watershed (PAMP) -0.5 -0.15 -0.17Year Dam Built 5 0.15 0.19Watershed Mines per Mile -2 -0.14 -0.01Number of Dams Upstream of Reservoir -0.22 -0.13 -0.06Reservoir Maximum Capacity 0 0.10 0.17Watershed Area/Reservoir Surface Area -0.11 -0.09 -0.19CA Hg Atm Dep Rate to the Reservoir Surface 0 0.08 0.12Reservoir Latitude 5 0.08 0.04Watershed Surface Area 0 -0.05 0.13All Hg Atm Dep Rate to the Watershed -1 -0.03 -0.02All Hg Wet Atm Dep Rate to the Reservoir Surface 0 -0.03 0.03Number of Productive Mines in Watershed -0.13 -0.03 -0.002Watershed Percent Wetlands -5 0.02 0.002All Hg Atm Dep Rate to the Reservoir Surface -1 0.02 -0.05All Hg Wet Atm Dep Rate to the Watershed 0 0.01 -0.04Watershed Percent Agriculture -5 0.01 0.08Reservoir Surface Area 0 0.01 0.05Number of Mines in Watershed (MRDS) 0 -0.002 -0.03* Highlighted environmental factors indicate statstically signficant correlations with fish tissue mercury concentrations for the parametric, non-parametric, or both analyses (using their respective two-sided tests of signficance, P < 0.05).
Table 1: Correlation coefficients for 350 mm standardized predatory fish [MeHg]
versus reservoir and watershed factors
Environmental Factors*Lambda Trans-
formation Correlation Coefficient
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
•37
Several tools: Select right tool(s) for each reservoir
one size fits all
Source control
Water chemistry(decrease methylation)
Fisheries management
•38
Potential Solutions toReduce Fish Mercury
Multiple factors → Multiple possible tools
•39
(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
Multiple factors → Multiple possible tools
•40
(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
•41
Reservoir fish MeHg compared to modeled 2001 atmospheric Hg deposition rate
No record of upstream
gold or mercury mines
At least 1 recorded upstream gold or mercury mine
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
USEPA’s REMSAD 2001 model output for atmospheric Hg deposition throughout the U.S.
•42
Overall, atm dep
rates low in CA
Some limited
areas rival atm
dep rates in
eastern U.S.
Source: USEPA 2008a (Figure 6-3c)
USEPA’s REMSAD 2001: % of atmospheric Hg deposition from sources CA regulators cannot regulate
•43
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
Sources of Hg in atmospheric deposition per USEPA’s REMSAD model output for 2001 & literature review
•44
Reservoir fish MeHg and
upstream mines
•45
Reservoir or lake with no upstream mines
Almost half of
reservoirs (~150)
exceed draft target
More than a third of
those (~60) do not
have upstream
mine sites No mines, high fish
MeHg
No mines, high fish
MeHg
Reservoirs with very high fish MeHg
•46
~60%~40%
Mine waste remediation is a useful tool, but benefits may take a while to observe in many downstream reservoirs
•47
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
Mine waste remediation is a useful tool, but benefits may take a while to observe in many downstream reservoirs
•48
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 emissionsProfile 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]