1. SF Bay Hg Coordination Meeting Feb 2009
Hg in SF Bay Cores
SF Bay Hg Coordination Meeting Feb 2009

2. Background USGS (1990) coring Why Recore? 90+ sites screened only
2 depositional sites fully characterized
Subsurface 2 sites
Pollutant reservoir?
Why Recore?
2 of 90 sites probably not representative
Old cores unusable for chem analyses

3. Core- What Is It Good For? (absolutely something)
Bay pollutant inventory
Erosional time bombs?
Model validation
Conceptual &/or mechanistic
Model development
Empirical, mechanistic, hybrid

4. Distribution of Sites (Bay)
Representative
inventory, sedimentation
3 sites Central Bay, 2 sites each other segments
Preference to RMP repeat stations

5. Distribution of Sites (Wetland)
Loading history
Depositional zones
1 site each segment
Pt Edith Martinez
Wildcat Richmond
Damon Sl. Oakland
Greco Island
Coyote Creek
Alviso Marina

6. Conceptual Model Sedimentation (from isotopes, bathymetric history)
Similar in segment (shared water, sediment)
But mesoscale differences (trib/shore proximity, etc)
Pollutant (Hg) distribution function of
Sedimentation history
Local land use/ loading

7. Dating: Bathymetric History
(USGS Bruce Jaffe)
Sum bathymetric changes between surveys
+ deposition – erosion
Some sites depositional & erosional different periods

8. Dating: Isotopes (USC Hammond) Cs in A-bomb Pb decay Cs & Pb similar
max ~1960
Pb decay
half life 22 yrs
Decay/ mixing dilution can look similar
Cs & Pb similar
likely mixing dilution

9. Results Sites within segments similar (from bathymetry and radiodates)
Suisun, San Pablo eroding
Central, South neutral/eroding
Lower South accreting
Wetland Hg indicates loading history
Subsurface max in wetlands everywhere
Layer often near surface (1950s?)

10. Lower South / South Bay 1960 = 30-60cm bay, 80cm wetland
Lower South / South Bay 1960 = 30-60cm bay, 80cm wetland cm bay, 30cm wetland
1960
1960
1960
1960

11. Central Bay 1960 = 5-20cm bay, ?? wetland

12. San Pablo & Suisun Bay 1960= 2-5cm bay, ??wetland 2-80cm?! bay, ??wetland

13. Results Bay core Hg often ~uniform, or complex
RMP segment avg ~ core top section
Weak/no subsurface max in Bay sites
Mixing, erosion (or ~constant loads)?
All could give ~uniform profile
Some sites not well predicted (esp SU002)
Bathymetry, Cs, Hg mismatch
Multiple deposition & erosion w/ seds from different watersheds

14. Implications? Few Hg ticking time bombs in Bay
So far, so good (2 of [ ])
Largely WYSIWYG (surface ~ middle)
Wetland cores capture historical pulses
Historical Hg loads mostly eroded, dispersed in Bay

15. Next Steps Finish wetland radiodating
More normalization? (high TOC in wetlands)
Model accretion vs mixing for isotopes (USC)
Understand data discrepancies
Analytical variation, spatial/temporal differences
Implications for other work
More coring, modeling
Partial report 2009 Q1, Pulse of Estuary
All done 2009 Q3?

17. SF Bay Hg Coordiantion Meeting Feb 2009 (RMP Annual Meeting Oct 2008)
SF Bay MeHg Mass Budget
SF Bay Hg Coordiantion Meeting Feb 2009
(RMP Annual Meeting Oct 2008)

18. WWMMBD? What Would the MeHg Mass Budget Do? Track MeHg specifically
MeHg <1% of totHg, poor MeHg:totHg correlation
Synthesize- do Bay data make sense given…
Loading, production, degradation, sed-water exchange, etc.
Quantitative dimension to MeHg
conceptual model
ID key factors for MeHg fate
Refined models feasibility/needs
E.g. temporal & spatial detail
What it won’t/can’t do
Turn water to wine (not J)
Identify “hot” spot impacts (1 box)
Predict long term (no Hg linkage)
Synth knowledge.
This essentially serves as a quantitative conceptual model of MeHg processes, helping us identify key factors
By developing an understanding how the model responds compared to the actual system, we can determine the feasibility…
WWMMBD?

19. MeHg 1 Box Model Many simple assumptions (from PCB 1 box)
One water compartment
One sediment compartment (10cm mixed layer)
Daily time step
Annually uniform loads (no seasonality)
Uniform mixing
Equilibrium partitioning
Long term steady state
Simplifications worked for PCBs, PBDEs
Can it work for MeHg?

20. Does It Work? - Reasonably
Base case = average
initial concentrations (from RMP monitoring)
loading/process parameter values
At steady state
Sediment mass ~
Water mass lower
Fast! <1 month

21. Base Case Run Mass (inventory) vs daily flux/degrade/produce
Water Mass
External load>, Net sediment to water exchange =
Degradation>, GG outflow, >> bio-uptake,volatilization
Total (Water+Sediment)
Production ~balances degradation >> all other processes
* Flux box within ~2x: ~.014 kg/d (Choe et al, N Bay)
Mass in water (kg)
0.38 kg
Ext load
0.024
kg/d
Sed to water
0.0064
Outflow
0.023
Water Degrade
0.0075
Fish uptake
.0001
Volatilization
<0.0001
Mass in Sediment
31.0
Methylate
1.82
Sed Degrade
1.80
Sed to Water
Burial
0.0074
If you’ll notice, the daily meth and degradation rates are only about 1 order of magnitude < than the inventory, which suggests That the system will respond very quickly changes in these parameters.

22. Parameter Sensitivity (Mass/Input) at ±3x default input
Input Parameter
Sediment
Water
Sediment meth rate
99.3%
66.0%
Sediment demeth rate
-96.5%
-64.1%
SSC
-0.8%
49.3%
External load
0.6%
31.1%
Long term net outflow
-0.5%
-23.5%
Tidal flushing ratio
-0.4%
-18.6%
Water column Kd
0.4%
-21.8%
Particle settling rate
-0.3%
16.0%
Sediment burial rate
-0.2%
-11.0%
Water demeth rate
-9.7%
Ocean MeHg conc
0.1%
3.2%
Sed/water transfer V
0.0%

23. WDMMBD? What Did the MeHg Mass Budget Do? Show Bay data reasonable
Base case ~T0 state- near “right” Baywide, but non-unique solution (e.g. offsetting errors?)
Feasibility/needs of refined model(s)
1 box driven by steady state/equilibrium
Basis for more detailed (time/space) model?
Much higher data needs
Key factors affecting mid term MeHg fate
External loads small/medium effect on Baywide scale
Very sensitive to de/meth rates
Even with this very crude 1 box model we are able to see that .. Ext loads have little effect, and the system is very sensitive to meth/demeth rates,
So naturally that leads us to questions of what management options we might explore given that…

24. Management Strategy – Dr. Evil
Acquire $1 Million
Option A- Control meth:
Sterilize Bay w/ thermonuclear device
Option B- Control Demeth:
Equip sharks w/ frickin UV lasers
If we left the strategy to Dr. Evil, we might end up with solutions like these

25. Management Strategy -RMP
Option C- RMP Mercury Strategy:
Where biota affected (food web entry)
ID disproportionate (high leverage) pathways
ID intervention opportunities
THEN act (e.g.holding ponds, aeration, dredging, nutrient reductions, sed amendments, etc)
Monitor & model management effectiveness “adaptive management”
(likely cost > $1 million)
But fortunately cooler heads prevail

26. Acknowledgements Too many to list…
“If I have seen further it is by standing on ye shoulders of Giants”
– Sir Isaac Newton
HGH? (not Hg) researcher
Although like any model it can be incrementally improved as we learn more

30. LSB Metals Downcore concentrations noisy
Coyote Creek Hg max > Alviso!
Coyote Hg 1960s depth (80cm)
Coyote Cu 40cm = 1980s?
~max Cu discharge late 1970s (Palo Alto)
~surface sediment Cu USGS long term data

31. SB001: Continuous Erosion?
Core ID: SB001,
X: , Y:
1858 depth: -122
1898 depth: -123
1931 depth: -157
1956 depth: -124
1983 depth: -146
2005 depth: -160
2006 depth: -161
Reconstructed horizons: 0
~0cm to ~15cm to 1960

32. SB002: No Change ~1950s
~0cm to ~12cm to 1960

33. SB Wetland Deposition
~30cm to 1960

34. South Bay Metals Downcore concentrations noisy
Cu Greco Island similar to Coyote, but into 1960s zone.
Greco Hg max ~constant in wetland to 55cm (1960s Cs penetration to 30cm) = 1930s?

35. CB001: No Change ~1940s
~0cm to ~5cm to 1960

36. CB002: Erosion to ~1920s
~0cm to ~20cm to 1960

37. CB006: Continuous Erosion
Core ID: CB006A,
X: , Y:
1858 depth: -106
1898 depth: -134
1931 depth: -132
1956 depth: -183
1983 depth: -220
Reconstructed horizons: 0
~0cm to ~12cm to 1960

38. Central Bay Metals
Bay downcore concentrations smaller range than in SB/LSB
No dating for wetland cores yet
~20cm surbsurface max for Hg, Se, Cu in wetland,
Similarly high conc for Se, surface, 60cm

39. SPB001: Erosion to ~1920s
~0cm to ~5cm to 1960

40. SPB002: Erosion to ~1880s
~0cm to ~2cm to 1960

41. San Pablo Metals ~20cm surbsurface max for Hg, Se, Cu in wetland
No dating for wetland cores yet
No secondary metal peaks
Deeper concentrations fairly constant

42. SU001: Erosion to ~1910s
~0cm to ~2cm to 1960

43. SU002: Erosion to ~1890s
~0cm to ~80cm to 1960?!!

44. Suisun Metals Hg highly variable @ Pt Edith and SU002
No dating for wetland cores yet
SU002 max concentrations in top section
Hg, Se, Cu, subsurface spikes as well