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 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