reservoir management strategies to reduce fish mercury levels€¦ · in santa clara valley water...

Reservoir Management Strategies to Reduce Fish Mercury Levels

California Statewide Mercury Control Program for Reservoirs

NALMS Symposium Nov. 1, 2013

Multi-Region Team Carrie Austin , Stephen Louie,

Michelle Wood, & many others •1


Goal: Quickly, measurably reduce fish MeHg

•2

Website with fact sheets & updates www.waterboards.ca.gov/water_issues/programs/mercury

•See Fact Sheet:

Outline

•3

Outline

•4

Methylmercury Production

Outline

•5

Multiple factors

Food Web Transfer


Limited benefits from source control

•6

Limited benefits from source control

•7

low sedHg, high fish MeHg

Manage redox conditions

Redox sequence:

O2 aerobic heterotrophs NO3

- denitrifiers MnO2(s) fermenters Fe(OH3)(s) fermenters SO4

2- sulfate reducers H+ methane producers

• Avoid

•Desirable

•8


Oxygenation: Session F2 Mercury Management 1

Hypolimnetic Oxygenation to Reduce Bioavailable Mercury in Santa Clara Valley Water Supply Reservoirs

The Effect of Oxygen, Nitrate and Aluminum Hydroxide on Methylmercury Efflux from Contaminated Profundal Lake Sediments

Efficacy of Hypolimnetic Oxygenation on Managing the Accumulation of Mercury in Lakes

Monitoring Effects of Hypolimnetic Oxygenation on Methyl Mercury in Fish in Water Supply Reservoirs

•9

Oxygenation Pilot Tests

Santa Clara Valley Water District • Solar-powered circulators • HOS line diffuser

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Solar-powered circulator MeHg

•Annual coincidence: MeHg & seasonal anoxia

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•Citation: Santa Clara Valley Water District

Citation: Dave Drury SCVWD

Santa Clara Valley Water District

•12

•HOS: •Hypolimnetic Oxygenation System

Full-scale oxygenation

Calaveras Reservoir

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Camanche Reservoir

Speece cone 2 mile DO plume

Bonus Methylmercury

Production

Effect of HOS on fish mercury

Manage redox conditions

Redox sequence:

O2 aerobic heterotrophs NO3

- denitrifiers MnO2(s) fermenters Fe(OH3)(s) fermenters SO4

2- sulfate reducers H+ methane producers

• Avoid

•Desirable

•14


15

Source Removal and Nitrate Addition Onondaga Lake, New York

Citation: Charles T. Driscoll Syracuse University

•16

•16

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0 1 2 3

Dep

th (m

)

10

12

14

16

18

20072008200920102011

MeHg (ng L-1)

0 1 2 3 0 1 2 3 4

August September October

18


0 1 2 3

Dep

th (m

)

10

12

14

16

18

20072008200920102011

MeHg (ng L-1)

0 1 2 3 0 1 2 3 4

August September October

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Manage fishery

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Food lower in MeHg

Cull fish

Select species

Food Web Transfer

Food lower in MeHg

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Fertilize ↑ Algae = MeHg

No more than 2x Chl-a and Chl-a ≤5 ug/L

1

•Algal Bloom Dilution

Food lower in MeHg

•22

Fertilize ↑ Algae = MeHg

1

Stock prey with low MeHg e.g., Rainbow trout

2

•Citation: Jesse Lepak

Cull or “intensive fishing”

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Select species

•24

Stock – hatchery diets low in MeHg

0

0.1

0.2

0.3

Stocked Resident

Rainbow trout

Citation: Mike Horvath, SFPUC

Select species

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0

0.5

1

1.5

200 600 1,000

Hg (m

g/kg

)

Length (mm) Land-Locked Anadromous

Chinook

Stock – hatchery diets low in MeHg

0

0.1

0.2

0.3

Stocked Resident

Rainbow trout

Restore native anadromous fish

Citation: Mike Horvath, SFPUC


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Source control manage expectations Pilot tests

Website with fact sheets & updates www.waterboards.ca.gov/water_issues/programs/mercury

Multiple factors

Upland and in-lake remediation areas

Isolation cap 172 ha

Thin layer cap 11ha

Groundwater barrier wall

Extensive remediation at former factory sites


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↓ Hg → reservoir (source control)

•29

Atmospheric Deposition

Mines mercury and gold

•30

Mercury from atmospheric deposition and mines

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

Multiple Factors

California: 350 reservoirs and lakes

•Average of highest trophic level

Multiple factors: fish species

0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10

% Rank

Average Fish MeHg Concentration (mg/kg)

Region 2Other Regions

Target 0.2 mg/kg

SF Bay Region: hotspot for

high fish mercury levels

•32

•Large dots: High prevalence of R2 reservoirs at

extreme of distribution

reservoir management strategies to reduce fish mercury levels€¦ · in santa clara valley water...

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