Polycyclic Aromatic Hydrocarbons in the San Francisco Estuary

Distributions, Trends, and Sources in Sediments (1993-2001)

Daniel R. Oros and John R.M. Ross

San Francisco Estuary Institute

7770 Pardee Lane, Oakland, CA 94621

9-Year Synthesis 1993-2001: PAH Series

Oros and Ross. PAH in SF Estuary sediments. Marine Chemistry 86:169-184, 2004.

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

Why are PAH of concern?

• Genotoxic

• Mutagenic

• Carcinogenic

• Ubiquitous

• Constant input (limited or no control of non-point sources)

• Regional Board’s Section 303(d) “Watch” List

How do PAH enter the estuary?

Trains

Ferries

Vehicular Traffic

Industrial Emissions

Fishing and Commercial Vessels

Combustion of Refined Petroleum Products

Natural and Intentional Burning of Biomass Fuels

Fireplaces

Natural Fires

Campfires

Uncontrolled and Accidental Input of Unburned Petroleum and its Refined Products

Asphalt and Lube Oil

Creosote Treated Pier Pilings

Spills (e.g., crude oil)

60,000 gallon diesel spill at Suisun Marsh April 27, 2004. Concern: Toxicity depending on exposure and dosageDiesel fate: dispersion, evaporation, and biodegradation.Photo credit: Kurt Rogers, San Francisco Chronicle

Examine PAH in sediments to determine:

• Spatial distributions

• Temporal trends

• Sources

Objective

Figure 1. Map of sediment sampling stations (1993-2001)

 

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

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

230217

96 87

31

0

50

100

150

200

250

CB SB NE ESB Delta

Estuary Segment

Me

an

To

tal

PA

H

(mg

/kg

TO

C)

Figure 2. Mean PAH distributions by segment

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

Results: Temporal Trends (1993-2001)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

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

Table 1. PAH isomer pair ratios of specific sources

Source An/178 BaA/228 Fl/Fl+Py IP/IP+BghiP

Petroleum (unburned) <0.10 <0.20 <0.40 <0.20Petroleum combustion 0.40-0.50 0.20-0.50Petroleum and combustion (mixed) 0.20-0.35Combustion >0.10 >0.35Biomass and coal combustion >0.50 >0.50

PAH Isomer Pair Ratio

• 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 (cont’d): Sources

An/178 (3 Rings)

2 1

100 98 99 100 100

0%

50%

100%

Delta NE CB SB ESB

Petroleum Combustion

BaA/228 (4 Rings)

24 5 4 1 9

76 95 96 99 91

0%

50%

100%

Delta NE CB SB ESB

Mixed Combustion

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

Estuary Segment

Fre

qu

en

cy (

%)

IP/IP+BghiP (6 Rings)

1

89 90 83 82 63

11 9 17 18 37

0%

50%

100%

Delta NE CB SB ESB

Petroleum Petroleum Combustion Biomass and Coal Combustion

Fl/Fl+Py (4 Rings)

10 12 4

81 78 92 91 91

10 10 8 5 9

0%

50%

100%

Delta NE CB SB ESB

Petroleum Petroleum Combustion Biomass and Coal Combustion

Figure 3 (cont’d). Bar plots showing frequency (%) of PAH from various sources in each segment

Estuary Segment

Fre

qu

en

cy (

%)

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

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 (cont’d)

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 (cont’d)

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 (cont’d)

This study was funded by the RMP as a contribution to the 9-Year Synthesis

Laboratory Analyses, Field Work and Data ManagementDr. 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 SciencesSarah Lowe (SFEI)Cristina Grosso (SFEI)

Scientific Peer-ReviewSFEI StaffThree “Unknown” Reviewers

Acknowledgements