Mercury Strategy Outline

1
Mercury Strategy Outline

• RMP CFWG
• September 14, 2007

2
CalFed Bay-Delta Mercury Strategy Core Components

• Quantification and evaluation of mercury and
  methylmercury sources
• Remediation of mercury source areas
• Quantification of effects of ecosystem
  restoration on methylmercury exposure
• Monitoring of mercury in fish, health-risk
  assessment, and risk communication
• Assessment of ecological risk
• Identification and testing of potential
  management approaches for reducing methylmercury
  contamination

3
Mercury Management Questions (Delta Tribs Mercury
Council)

• What is the nature and extent of the human health
  and ecological risks caused by mercury in the
  Sacramento River Watershed and downstream waters?
• How well understood is the nature of mercury risk
  and the ability to reduce it?
• What is a prudent course of action to reduce
  mercury risk in the SRW?

4
Delta Tribs Mercury Council Knowledge Gaps

• RMP likely to encounter similar gaps
• Sources- loads from air, native soils, hot
  springs, mine tailings, bioavailability of diff
  source types
• Transport/transformation- water quality effects
  on MeHg loads, uptake from various tribs,
  locations
• Hg exposure various locations- food chain
  relationships, human consumption
• Risk for given exposures- demonstrated effects of
  mercury in humans and wildlife

5
RMP Mercury Management Questions

• Where is mercury entering the food web?
• Which sources, processes, and pathways contribute
  disproportionately to food web accumulation?
• Can we do anything about these high-leverage
  processes, sources, and pathways?
• What effects can be expected from management
  actions?
• Will total mercury reductions result in reduced
  food web accumulation?

6
Where is mercury entering the food web?

• Spatial and temporal dimensions to the question
• General vs hotspot priority (target species,
  random vs fixed site)
• Much of Bay above targets
• Food web accumulation hotspots
• Methylation hotspots

7
Which sources, processes, and pathways contribute
disproportionately to food web accumulation?

• Sources- is all Hg ultimately bioavailable (for
  methylation, uptake)?
• Processes- what (co)factors affect transport,
  transformation, uptake (what spatial and temporal
  scales of interest)?
• Bioaccumulation- biggest jumps at lowest trophic
  levels (primary producer)

8
Can we do anything about these high-leverage
sources, processes, and pathways?

• Sources- Reduce totHg? Selected reactive
  souces?
• Processes- Adjust (co)factors (aeration,
  flushing, nutrient loading)
• Bioaccumulation- choose species, habitat design?
  (likely least flexibility?)

9
What effects can be expected from management
actions?

• Implies need to model questions 1 3?
• Possible with conceptual or semi-quant models?
• Interpret monitoring data?
• Pre- post- action
• Appropriate spatial and temporal scales (with
  associated variability) 

10
Will total mercury reductions result in reduced
food web accumulation?

• Currently tot Hg reductions the largest component
  of management strategy
• A form of MQ 2 (which sources.. contribute to)
• Experimental or field approaches may be valuable

11
How to prioritize?

• RMP Qs 2, 3, currently least known
• Large factors, large uncertainties first
• Portion of Hg convertible to MeHg
• MeHg sources- in situ production, sed-water
  exchange, tributary loads,
• Loss pathways- degradation, export
• MeHg mass budget tool to ID gaps
• Illustrating sensitivity to uncertainties