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Polycyclic Aromatic Hydrocarbons in the San Francisco Estuary Distributions, Trends, and Sources in Sediments (1993-2001) Daniel R. Oros and John R.M.

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Presentation on theme: "Polycyclic Aromatic Hydrocarbons in the San Francisco Estuary Distributions, Trends, and Sources in Sediments (1993-2001) Daniel R. Oros and John R.M."— Presentation transcript:

1 Polycyclic Aromatic Hydrocarbons in the San Francisco Estuary Distributions, Trends, and Sources in Sediments ( ) Daniel R. Oros and John R.M. Ross San Francisco Estuary Institute 7770 Pardee Lane, Oakland, CA 94621

2 9-Year Synthesis : PAH Series Oros and Ross. PAH in SF Estuary sediments. Marine Chemistry 86: , Ross and Oros. PAH in the in SF Estuary water column. Submitted to Chemosphere Oros and Ross. PAH in SF Estuary bivalves. Submitted to Marine Environmental Research

3 Why are PAH of concern? Genotoxic Mutagenic Carcinogenic Ubiquitous Constant input (limited or no control of non-point sources) Regional Boards Section 303(d) Watch List

4 How do PAH enter the estuary? Trains Ferries Vehicular Traffic Industrial Emissions Fishing and Commercial Vessels Combustion of Refined Petroleum Products

5 Natural and Intentional Burning of Biomass Fuels Fireplaces Natural Fires Campfires

6 Uncontrolled and Accidental Input of Unburned Petroleum and its Refined Products Asphalt and Lube Oil Creosote Treated Pier Pilings Spills (e.g., crude oil)

7 60,000 gallon diesel spill at Suisun Marsh April 27, Concern: Toxicity depending on exposure and dosage Diesel fate: dispersion, evaporation, and biodegradation. Photo credit: Kurt Rogers, San Francisco Chronicle

8 Examine PAH in sediments to determine: Spatial distributions Temporal trends Sources Objective

9 Figure 1. Map of sediment sampling stations ( )

10 Methods: Spatial Distributions 25 PAH were summed ( PAH) for each station PAH concentrations were normalized to TOC content (significant relationship) Stations were grouped into 5 segments: Delta, North Estuary, Central Bay, South Bay, and Extreme South Bay Comparisons between segments, seasons, and stations were conducted using the non-parametric Kruskal-Wallis test

11 Results: Spatial Distributions Central Bay and South Bay PAH were significantly higher than North Estuary, Extreme South Bay, and Delta South and Central Bays were not significantly different Delta was significantly lower than all other segments Figure 2. Mean PAH distributions by segment

12 Methods: Temporal Trends PAH concentrations were first normalized to TOC and % fines content by multiple linear regression analysis Trends for PAH were examined for each station by linear regression analysis using the ln(rescaled residual) as the dependent variable and sampling date as independent variable A significant positive slope (p<0.05) indicated an increase, a significant negative slope a decrease, and a lack of significance no detectable trend in PAH at a station over time

13 Results: Temporal Trends ( ) Station Analysis A statistically significant (p<0.05) decreasing trend in PAH was found only at San Pablo Bay (1 of 26 stations) No trends were detected at any other stations, which suggests that PAH levels remained constant over the 9 year period Seasonal Analysis Sacramento River and Oyster Point showed significantly higher PAH in the wet season than the dry season. No significant seasonal differences were found at other stations

14 Methods: Sources PAH isomer pair ratios were used as diagnostic indicators to identify possible sources. Isomers have similar partitioning behavior and solubility. Anthracene / Anthracene + Phenanthrene Benz[a]anthracene / Benz[a]anthracene + Chrysene Fluoranthene / Fluoranthene + Pyrene Indeno[1,2,3-c,d]pyrene / Indeno[1,2,3-c,d]pyrene + Benzo[g,h,i]perylene

15 Table 1. PAH isomer pair ratios of specific sources

16 Bar plots of PAH isomer pair ratios were generated to show estimated frequency (%) of PAH from the various sources in each segment PAH isomer pair ratios determined from estuary were compared to PAH isomer pair ratios from known environmental, petroleum, and single-source combustion sources compiled from the scientific literature by Yunker et al. (2002) Methods (contd): Sources

17 Figure 3. Bar plots showing frequency (%) of PAH from various sources in each segment Estuary Segment Frequency (%)

18 Figure 3 (contd). Bar plots showing frequency (%) of PAH from various sources in each segment Estuary Segment Frequency (%)

19 Summary and Conclusions Mean PAH was significantly higher in the Central and South Bays compared to the North Estuary, Extreme South Bay and Delta. Delta was significantly lower than all others Distribution could reflect the large amount of urbanized area that surrounds Central and South Bays and the less urbanized area in the Delta

20 A significant decreasing trend in PAH levels was found at San Pablo Bay PAH decreasing trend is consistent with previous observations that San Pablo Bay is eroding due to diminished sediment supply and as currents and waves transport sediment from the bay (Jaffe et al., 1998, USGS) No trends were found at any other stations Estuary PAH levels remained constant, which is consistent with other national studies that reported no increasing or decreasing trends for PAH Summary and Conclusions (contd)

21 Sacramento River and Oyster Point showed significantly higher PAH in the wet season than the dry season. No significant seasonal differences at other stations Location near freshwater discharges and estuary margins is an important determinant of PAH sediment concentration Summary and Conclusions (contd)

22 PAH sources were identified by PAH isomer pair ratio analyses using values compiled by Yunker et al. (2002) Petroleum and Fossil Fuel Combustion gasoline, diesel, crude oil, and coal (e.g., coal from historical use) Biomass Burning wood, wood soot, and grasses Unburned Petroleum shale oil, lube oil, and creosote (e.g., shale oil from refined Monterey oil) Summary and Conclusions (contd)

23 This study was funded by the RMP as a contribution to the 9-Year Synthesis Laboratory Analyses, Field Work and Data Management Dr. Robert Risebrough (Bodega Bay Institute) Dr. Jose Sericano (GERG, Texas A&M) Dr. Francois Rodigari (EBMUD & BACWA) Genine Scelfo (UCSC) Capt. Gordon Smith (RV David Johnston) Applied Marine Sciences Sarah Lowe (SFEI) Cristina Grosso (SFEI) Scientific Peer-Review SFEI Staff Three Unknown Reviewers Acknowledgements

24


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