Slide 1 Mercury Control Program for the Sacramento-San Joaquin River Delta Estuary San Francisco Bay...
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Transcript of Slide 1 Mercury Control Program for the Sacramento-San Joaquin River Delta Estuary San Francisco Bay...
Slide 1
Mercury Control Program for the Sacramento-San Joaquin
River Delta Estuary
San Francisco Bay RMP Annual Meeting
October 7, 2008
Michelle Wood
Slide 2
OutlineDescription of the Delta Mercury
ImpairmentOverview of Proposed
Delta Program
Comparison to RMP Mercury Strategy’s High Priority Questions
Questions & Discussion
Slide 3
The Delta
R
S
F
>1100 mi waterwaysDrains ~1/3 of CA
Reg
ion
5
Sacramento
Tracy
StocktonAntioch
Brentwood
Reg
ion
2
San Francisco BayHg Control Program:
ReduceCentral Valley
Mercury Outflows by 110 Kg/year110 Kg/year
Slide 4
Who eats Delta fish?
Wildlife:
Least tern, kingfisher, western grebes, bald eagle, osprey,
& river otter
Slide 5
Who eats Delta fish?
~300,000 licensedsport & subsistence
anglers per year
Unknown # of unlicensed anglers
Multiple ethnicities, communities,& income levels
5% of fish consumers in northern Delta: mercury intake rate 10x the safe dose
Slide 6
Goal of the ProposedDelta Mercury Program:
Protect fish-eating wildlife& enable humans to safelyconsume more Delta fish.
Slide 7
Proposed Fish TissueHg Objective for Delta Fish
0.24 mg/kg mercuryin large bass & catfish
1 meal (8 oz)
per week
Slide 8
Average Hg Levelsin Large Bass & Catfish(mg/kg)
0.26na
0.50
0.56
0.92
na
0.32
Proposed Objective:
0.24 mg/kg
Slide 9
Mercury Strategy for the Bay-Delta Ecosystem (CalFed, 2003):
“The problem with mercury in the Delta’s aquatic ecosystems can be
defined as biotic exposure to methylmercury.”
MeHg = most toxic, bioavailable form of Hg
>90% of Hg in fish = MeHg
Slide 10
TributaryMeHg
Surface
Sediments
Pore WaterExchange &
Diffusion
bacterial methylation
Hg MeHg
MeHg
OpenChannel
Wetlands
Urban & WWTPs
Agricultural Lands /Delta Islands
Slide 11
How do we reducefish MeHg levels?
Local & nationwide studies: Most important, single factor in determining how much MeHg is in fishis water MeHg concentration
Most direct way to reduce fish MeHg is to reduce the concentration of MeHg in water
Slide 12
MeHg Linkage: Largemouth Bass & Average Water MeHg
R2 = 0.91
0.0
0.5
1.0
0.0 0.1 0.2
Water MeHg (ng/l)
Bas
s H
g (m
g/kg
)
y = 20.365x 1.6374
Slide 13
MeHg Linkage: Largemouth Bass & Average Water MeHg
R2 = 0.91
0.0
0.5
1.0
0.0 0.1 0.2
Water MeHg (ng/l)
Bas
s H
g (m
g/kg
)
0.24 mg/kg
0.066 ng/l
y = 20.365x 1.6374
Slide 14
Proposed MeHg Goal 0.06 ng/l in unfiltered ambient water, annual
average Establishes the assimilative capacity Used to determine how much reduction from
MeHg sources is needed to achieve fish tissue objective
Slide 15
0.16
0.11
0.17
0.08
0.22
Average Annual
Ambient MeHg Levels
in Water(ng/l)
0.06
0.270.27
Slide 16
MeHgSource
Reductions Needed to Achieve
Proposed0.06 ng/l goal
78%
0%
63%
45%
65%
73%
25%0%
25%
78%
Slide 17
Proposed Control StrategyReduce Hg in sediment
(reduces MeHg produced by Delta wetlands& open-water areas)
Control activities that enhanceproduction of (and degrade) MeHg in wetlands & open-water areas
Reduce MeHg dischargesfrom external sources(e.g., WWTPs, urban runoff & irrigated agriculture)
Slide 18
Delta TMDL Adaptive Approach
~2009 Phase 1 Phase 2
Studies
Implement Hg pollution prevention measures
Improve CC Settling Basin
Identify other high-priority legacy Hg projects
Develop upstream TMDLs
Conduct pilot offset projects
Re-
asse
ss M
eHg
Re-
asse
ss M
eHg
allo
catio
ns &
sch
edul
es.
allo
catio
ns &
sch
edul
es.
Implement MeHg controls in the Delta & upstream watersheds
Continue to implement legacy Hg projects
Long-term offset projects
~2017
TMDLReview
Slide 19
OutlineDescription of the Delta Mercury ImpairmentOverview of the Proposed
Delta Program
Comparison to RMP Mercury Strategy’s Comparison to RMP Mercury Strategy’s High Priority QuestionsHigh Priority Questions
Questions & Discussion
Slide 20
RMP Priority Questions
1. Where and when does mercury enter the food web?
We have a general idea of the “where” in the main channels
Slide 21
CalFed Mercury ProgramFish Sampling
Average Hg Concentrations in largemouth bass, 2000
(Davis et al., 2003)
Inland silverside Hg & MeHg Concentrations, Fall 1999
(Slotton et al., 2002)
Lower fish Hgin Central Deltaduring relativelylow-flow years
Lower fish Hgin Central Deltaduring relativelylow-flow years
Elevatedfish Hgin Delta
periphery
Slide 22
RMP Priority Questions1. Where and when does mercury enter
the food web? We have a general idea of the “where” in the
main channels
Does MeHg uptake into biota occur preferentially during some seasons?
— Recent CalFed study results from Darrell Slotton and others indicate increases in biosentinel fish and water MeHg have been associated with floodplain inundation that occurred in different times of the year
Slide 23
RMP Priority Questions2. Which processes, sources & pathways
contribute disproportionately to food-web accumulation?
RMP isotopic composition study of mercury to determine which mercury inputs are contributing most to bioaccumulation
— Useful for both Bay & Delta programs!— Compliments the proposed Delta program’s focus on
identifying the MeHg sources to the Delta & the inorganic Hg sources that supply the MeHg sources
Slide 24
RMP Priority Questions2. Which processes, sources, & pathways
contribute disproportionately to food-web accumulation?
We have a general idea of which sources contribute MeHg & TotHg to the different areas of the Delta
Sources that cause the impairment in different Delta areas come from different places
We need seven different area-specific control strategies
Slide 25
Seven Control
Programsin One…
…because different areas of the Deltaare dominated by
different MeHg & TotHg
sources
Yol
o B
ypas
s
Southern
Delta
Slide 26
RMP Priority Questions2. Which processes, sources, & pathways
contribute disproportionately to food-web accumulation?
Need to refine load estimates for wetlands in the Delta & upstream watersheds
Slide 27
RMP Priority Questions3. What are the best opportunities for
management intervention for the most important pollutant sources, pathways & processes?
4. What are the effects of management actions?
Proposed Delta TMDL implementation plan includes studies to address these questions.
Yolo Bypass wetland management practice study is already underway
Slide 28
RMP Priority QuestionsQuestions 3 & 4
Key observations for the Delta: Tributary watersheds account for most of
the MeHg inputs to the Delta
No one point or nonpoint source - individual or by category - in the Delta or its upstream watersheds causes the impairment
Slide 29
RMP Priority QuestionsQuestions 3 & 4
Key observations for the Delta:
All wetlands are not alike: some act as big sources, some as small sources, and some as sinks
All WWTPs are not alike: some have low effluent MeHg, others high
Slide 30
RMP Priority QuestionsQuestions 3 & 4
Key observations for the Delta:
Two recent studies support the hypothesis that MeHg in ambient water is a primary factor in determining how much MeHg is in fish
Slide 31
(1) Floodplain Inundation on theSan Joaquin River: Before & After
San Joaquin River @ Vernalis
0
50
100
150
200
250
300
Sil
vers
ide M
eH
g (
mg
/kg
)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Wate
r M
eH
g (
ng
/l)
Silverside fish
water
Slide 32
RMP Priority QuestionsQuestions 3 & 4
Key observations for the Delta: Two recent studies support the hypothesis that
MeHg in ambient water is a primary factor in determining how much MeHg is in fish
2) Local bioaccumulation study: WWTP effluent contributes about the same amount of mercury to Sacramento River bioaccumulation as expected from its effluent methylmercury loads
Slide 33
RMP Priority QuestionsQuestions 3 & 4
Proposed Delta control program does not attempt to indicate which MeHg
sources are more important because: No one source type or individual source causes the
impairment
We need additional characterization studies, especially for wetlands
We don’t know yet which inorganic Hg & MeHg sources will be the most feasible to reduce [in terms of efficacy, economics & environmental impacts associated with particular controls and management practices]
Slide 34
RMP Priority Questions5. Will total mercury reductions result
in reduced food web accumulation?
Another good question!
Further, if “yes”,
can we reduce total Hg sources enough to accomplish desired
fish MeHg reductions?
Slide 35
Questions & Comments
Updates, reports & comments:
http://www.waterboards.ca.gov/centralvalley/
water_issues/tmdl/central_valley_projects/delta_hg/
Slide 36
Slide 37