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Mercury Strategy Outline. RMP CFWG September 14, 2007. 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

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Mercury strategy outline

Mercury Strategy Outline

RMP CFWG

September 14, 2007


Calfed bay delta mercury strategy core components
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


Mercury management questions delta tribs mercury council
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?


Delta tribs mercury council knowledge gaps
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


Rmp mercury management questions
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?


Where is mercury entering the food web
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


Which sources processes and pathways contribute disproportionately to food web accumulation
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)


Can we do anything about these high leverage sources processes and pathways
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?)


What effects can be expected from management actions
What effects can be expected from management actions? processes, and pathways?

  • 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) 


Will total mercury reductions result in reduced food web accumulation
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


How to prioritize
How to prioritize? accumulation?

  • RMP Q’s 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


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