Mercury in SF Bay The 8-Minute

Conceptual Model

California Regional Water Quality Control BoardSan Francisco Bay Region

RMP Annual MeetingMay 4, 2004

Richard Looker (rel@rb2.swrcb.ca.gov)

2

The 30 Second Conceptual Model

Bacteria in wetlands, mudflats and sloughs

Mercury in sediment

Methylmercury available for bioaccumulation

Mercury Discharges(Elemental and Inorganic)

Methylating Regions--

1. Mass budget

3. Bioaccumulation

2.Transformations & Transport

• Significance and magnitude of loads?

• Variability and Predictability of Loads?

• Details of the active sediment layer?

Inputs ~ 1200 kg/yr:

Outputs ~ 1700 kg/yr:

~ 100 kg Hg in Water

~ 60,000 kg Hg in Active Sediment

~ 10,000 kg Hg In Air Shed (20 km top)1. Mass Budget

15 cmActive Sediment

• Where is methylation happening? (controlling factors?)

• Transport details? (erosion, sediment movement?)

Hg in Water

2. Transformations & Transport

Me-Hg inBenthos

Me-Hg inSediment

Hg inSediment

Deposition Evasion

Export

BurialErosion

Me-Hg inWater

Me-Hg inFish

Import

Active Sediment

• What is the food web structure?

• What are food web concentration patterns?

3. Bioaccumulation(Me-Hg concentrations

shown relative to water)

Me-Hg inWater

Me-Hg inSediment

1

10

100-200

??

200

3000

Eggs: 6000

6

Wildlife and Fish Tissue are Indicators of Impairment

Too much Hg in fish – TMDL target is 0.2 ppm

Too much Hg in bird eggs– TMDL target < 0.5 ppm

Indicators for Management– Concentrations in small and large fish– Bird egg concentrations– Prey items for birds, fish– Sediment Me-Hg, Total Hg

7

What RMP Can/Could Do to Help

Gather risk management information (5 yrs.)– Fish consumption patterns among humans– Contamination patterns

Track food web concentrations (5 yrs.) Track bird egg concentrations (5 yrs.) Investigate significance of sources (5 yrs.)

– Relative bioavailability (from chemistry)– Residence time issues (from transport)

Keep on sampling water, sediment, fish

8

What RMP Could Do To Help (but needs some help to do it)

Coordinate Hg-related research (ASAP)– Disseminate results– Ensure intercomparability of results– Ensure research addresses management needs

There is currently no coordination between large number of research efforts.

We will not have another chance like this in terms of resources so there is a desperate need to make the most of this opportunity.