Source: U.S.G.S./Center For Land Use Interpretation

1. A mass balance model for the fate of PAHs in the San Francisco EstuaryBen K. GreenfieldJay A. DavisSan Francisco Estuary InstitutePresented at the Calfed Science Conference, January, 2003

2. Source: U.S.G.S./Center For Land Use Interpretation

4. Population Growth, Bay Area - 1860 to 2000 Data Source: MTC and ABAG, 2002 7,000,000 6,000,000 5,000,000 4,000,000 3,000,000 2,000,000 1,000,000 0 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 (Each Color is a Bay Area County)

5. Mass balance models • Understand compound fate • Identify research priorities (e.g. chemical properties) • Synthesize available data • Estimate loading rate

6. Simple mass balance model • Mackay et al. (1994) • Equilibrium partitioning based on chemical properties • Single pool of interacting water and sediment • Daily rate constants • Spreadsheet format

7. Volatilization Combined External Loads PAH Dissolved Outflow Particulate PAH Water Diffusion Degradation Deposition And Active Resuspension PCB PAH Dissolved Dissolved Sediment Layer Sorbed Sorbed PAH PAH Degradation Degradation Buried Sediment Burial

8. 2 ring – naphthalene • 3 ring – phenanthrene • 4 ring – fluoranthene and • benz(a)anthracene • 5 and 6 ring – e.g. benzo(b)fluoranthene Fluoranthene Benz[a]anthracene

9. Turnover Rate 100 PAH in Bay Percent Original Mass 50 Naphthalene Phenanthrene Fluoranthene Benz(a)anthracene Benzo(b)fluoranthene 0 0 1 2 3 4 5 Year

10. 100 Phenanthrene Fluoranthene Benzo(b)fluoranthene 75 PCB 118 PCB 118 Percent Original Mass 50 PAHs 25 0 0 5 10 15 20 Year

11. Loss Pathways of PAH Mass in Estuary Assuming No Load (One Year Simulation) 1.0 0.8 Volatilization Outflow 0.6 Proportion of Total Degradation Mass Remaining 0.4 0.2 0.0 N F B(a)a B(b)f Compound

12. 10 1 0.1 Degradation Rate (d-1) 0.01 0.001 0.0001 N P F B(a)a B(b)f Da B(a)p Compound

13. Sensitivity to Different Chemical Parameters Uncertainty for Benzo(b)fluoranthene Vary by PAH Compound 100 100 80 80 60 60 Proportion of Total 40 40 20 20 0 0 Kow Kow Air Side MTC Air Side MTC Water Side MTC Degradation Water Water Side MTC Degradation Sediment Degradation Water Henry's Law Constant Degradation Sediment Henry's Law Constant

14. Inputs? Loading Point Source Air Deposition Rivers Storm Drains Losses Degradation Volatilization Outflow Burial Trend?

15. Inputs? Loading? Losses Degradation? Volatilization Outflow Burial Trend?

16. Sediment Trends BivalveTrends 2000 6000 1800 5000 1600 1400 4000 1200 Total PAHs (µg/kg) 1000 3000 Total PAHs (mg/kg lipid) 800 2000 600 400 1000 200 0 0 1990 1992 1994 1996 1998 2000 2002 1993 1994 1995 1996 1997 1998 1999 2000 2001 Year Year

17. 1990 1980 Dated Sediment Core Chemistry From Pereira, W.E., et al. 1999 Marine Chemistry

18. Inputs? Loading? Losses Degradation? Volatilization Outflow Burial Trend?

19. Literature Estimates

20. Result summary Loss rates (half life) • 2 ring PAH - 3 week • 4 ring PAH - 1 year • 5 ring PAH - 6 years • Degradation rate uncertainty causes considerable model uncertainty • Obtained upper bound on degradation rate and lower bound on loading rate

21. Significance of findings • Much more rapid expected response to management changes than PCBs • Future priorities: • Local degradation rates • Dr. Michael Montgomery (NRL) - experimental data on Bay sediments • Local sediment-water partitioning

23. Acknowledgments • Don Yee • Jon Leatherbarrow • Sarah Lowe • Cristina Grosso • Patricia Chambers