Hg in SF Bay Cores SF Bay Hg

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

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

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

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

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

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

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

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

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 (1950 s? )

Lower South / South Bay 1960 = 30 -60 cm bay, 80 cm wetland 12 -15 cm bay, 30 cm wetland 1960

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

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

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 SU 002) • Bathymetry, Cs, Hg mismatch • Multiple deposition & erosion w/ seds from different watersheds

Implications? • Few Hg ticking time bombs in Bay – So far, so good (2 of [90 + 11]) – Largely WYSIWYG (surface ~ middle) • Wetland cores capture historical pulses • Historical Hg loads mostly eroded, dispersed in Bay

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 Q 1, Pulse of Estuary – All done 2009 Q 3?

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

WWMMBD? What Would the Me. Hg Mass Budget Do? • Track Me. Hg specifically – Me. Hg <1% of tot. Hg, poor Me. Hg: tot. Hg correlation • Synthesize- do Bay data make sense given… – Loading, production, degradation, sed-water exchange, etc. • Quantitative dimension to Me. Hg conceptual model – ID key factors for Me. Hg 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) WWMM BD?

Me. Hg 1 Box Model • Many simple assumptions (from PCB 1 box) – – – – One water compartment One sediment compartment (10 cm 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 Me. Hg?

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

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 ~2 x: ~. 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 kg/d Outflow 0. 023 kg/d Water Degrade 0. 0075 kg/d Fish uptake . 0001 kg/d Volatilization <0. 0001 kg/d Mass in Sediment 31. 0 kg Methylate 1. 82 kg/d Sed Degrade 1. 80 kg/d Sed to Water 0. 0064 kg/d Burial 0. 0074 kg/d

Parameter Sensitivity ( Mass/ Input) at ± 3 x 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 -0. 2% -9. 7% Ocean Me. Hg conc 0. 1% 3. 2% Sed/water transfer V 0. 0%

WDMMBD? What Did the Me. Hg Mass Budget Do? • Show Bay data reasonable – Base case ~T 0 state- near “right” Baywide, but nonunique 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 Me. Hg fate – External loads small/medium effect on Baywide scale – Very sensitive to de/meth rates

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

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)

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

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

SB 001: Continuous Erosion? Core ID: SB 001, X: 564867. 30345800000, Y: 4163027. 6190000 1858 depth: -122 1898 depth: -123 1931 depth: -157 1956 depth: -124 1983 depth: -146 2005 depth: -160 2006 depth: -161 Reconstructed horizons: 0 ~0 cm to 1960 ~15 cm to 1960

SB 002: No Change ~1950 s ~0 cm to 1960 ~12 cm to 1960

SB Wetland Deposition ~30 cm to 1960

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

CB 001: No Change ~1940 s ~0 cm to 1960 ~5 cm to 1960

CB 002: Erosion to ~1920 s ~0 cm to 1960 ~20 cm to 1960

CB 006: Continuous Erosion Core ID: CB 006 A, X: 566290. 21976900000, Y: 4174242. 03589000000 1858 depth: -106 1898 depth: -134 1931 depth: -132 1956 depth: -183 1983 depth: -220 Reconstructed horizons: 0 ~0 cm to 1960 ~12 cm to 1960

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

SPB 001: Erosion to ~1920 s ~0 cm to 1960 ~5 cm to 1960

SPB 002: Erosion to ~1880 s ~0 cm to 1960 ~2 cm to 1960

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

SU 001: Erosion to ~1910 s ~0 cm to 1960 ~2 cm to 1960

SU 002: Erosion to ~1890 s ~0 cm to 1960 ~80 cm to 1960? !!

Suisun Metals • Hg highly variable @ Pt Edith and SU 002 – No dating for wetland cores yet • SU 002 max concentrations in top section – Hg, Se, Cu, subsurface spikes as well