The Fate of the Oil Spilled from the Exxon Valdez ... - ACS Publications

S. RICE. National Oceanographic and. Atmospheric Administration ... I = Floating in Prince William Sound (PWS); 2 = evaporated hydrocarbons; 3 = atmos...
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The Fate of the Oil Spilled from the Exxon Valdez The Mass Balance Is the Most Complete and Accurate of Any Major Oil Spill

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ust after midnight on March 24, 1989, the 987-foot tank vessel Exxon Valdez

The overall mass balance for the Exxon Valdez oil (Figure 1) shows the time courses for several major components of the spilled oil and their geographic distribution (inside vs. outside of PWS). The logarithmic time scale extends from about 2:30 AM on March 24, 1989, to October 1, 1992. Many of the estimates represented here are based on

grounded on Bligh Reef in Prince William Sound (PWS), Alaska, releasing a p p r o x i mately 10.8 million gallons (-35,500 metric tons) of North Slope crude oil into the Sound. During the following eight weeks, oil was spread by winds and currents into the Gulf of Alaska (GOA) and along about 1750 km of shoreline, extending up to 750 km from the original spill site {1-3). We have analyzed published and unpublished information on the various processes that affected the distribution and transformations of the spilled oil and reconstructed a spatial—temporal mass balance up through the summer of 1992 (4). In this article, we present our conclusions and a brief overview of the supporting observations. Other authors have reviewed the wide variety 0013-936X/94/0927-561A$04.50/0 © 1994of American physical, chemical, and biological processes that begin almost immediately to transport and transform crude oil when it is introduced into the marine environment (5-10).

DOUGLAS A. WOLFE M. J . H A M E E D I National Oceanographic and Atmospheric Administration Silver Spring, MD 20910

G.

J. A. GALT WATABAYASHI

National Oceanographic and Atmospheric Administration Seattle, WA 98115

J.

SHORT C. O ' C L A I R E S. R I C E National Oceanographic and Atmospheric Administration Auke Bay, AK 99821

Chemical Society

well-understood phenomena and are supported by direct measurements or observations. For others, however, quantitative information is almost entirely lacking, and the values shown are reasoned estimates that illustrate approximate ranges. The estimates for various compartments and processes have been reconciled with one another to derive the most accurate "big picture" of the oil's fate. Nonetheless, the mass balance must be viewed as somewhat speculative, requiring critical d i s c u s s i o n of the data sources and uncertainties associated with the estimates. Transport and transformations of the surface slick Figure 1 depicts the spill with a uniform rate of release for 5 hours after the grounding of the ship [1,

J.

MICHEL

Research Planning, Inc. Columbia, SC 29201

J.

R. P A Y N E

Sound Environmental Services, Inc. Carlsbad, CA 92008

J.

BRADDOCK

University of Alaska Fairbanks, AK 99775

S.

HANNA

Sigma Research Corporation Concord, MA 01742

D.

SALE

Snow Otter Consulting Anchorage, AK 99501

Environ. Sci. Technol., Vol. 28, No. 13, 1994

561 A

FIGURE 1

The fate of Exxon ValdezoW: Overall mass balance from March 24,1989 to October 1,1992 Evaporated and photolysis products

Skimmed Beached GOA

Beached PWS

Dispersed

1000 Time (days) I = Floating in Prince William Sound (PWS); 2 = evaporated hydrocarbons; 3 = atmospheric photolysis products; 4 = dispersed in PWS; 5 = floating in Gulf of Alaska (GOA); 6 = dispersed in GOA; 7 = beached in PWS; 8 = beached in GOA; 9 = retrieved by skimmers; 10 = biodegraded in water; I I = biodegraded on PWS beaches; 12 = biodegraded on GOA beaches; 13 = retrieved (cleaned up) from PWS beaches; 14 = retrieved from GOA beaches; 15 = eroded and dispersed from GOA beaches; 16 = eroded from PWS beaches to shallow subtidal zone; 17 = oil residuals to offshore sediments. Greater detail is provided for the "Beached-PWS* section of this mass balance in Figure 2.

11). Appreciable evaporation occurred before all the oil escaped from the ship. The distribution of floating oil over time was quantitatively hindcast using the National Océanographie and Atmospheric Administration's (NOAA's) OnScene Spill Model (OSSM). The model output was reconciled with oil distributions observed from surveillance overflights of the spill area, and the model was periodically reinitialized to improve the fit [12, 13). This hindcast generated statistical estimates of the distribution of the floating (and initially beached) oil used in reconstructing oil fate. For most of the first three days after the spill, winds were quiet (generally 5—10 knots), the sea was calm in PWS, and the oil slick was concentrated in open water near the grounded ship. In the mid-afternoon of the third day (March 26), however, winds rose to 20—25 knots and were sustained (with gusts of 50—70 knots) over the next 3 days, moving the oil rapidly to the southwest and driving it ashore on Naked, Eleanor, Smith, Ingot, and 562 A

Knight Islands. Substantial quantities of the oil evaporated or were dispersed into the water column during this period. By March 30, the leading edge of the floating oil had passed from Montague Strait into the GOA [3, 12). For the next three weeks, oil was repeatedly deposited, refloated, and redeposited on affected shorelines in PWS as local winds and tides shifted. During this period, floating oil continued to drift from PWS into the GOA, where it floated in windrows and patches of mousse [a viscous water-in-oil emulsion containing up to 70% water [14)] and grounded on the exposed headlands along the Kenai Peninsula. Gale force (40—70 knot) winds churned the GOA along the Kenai coast April 9—10. The floating oil reached the Chugach and Barren Islands at the entrance to Lower Cook Inlet April 18-19, entered the Shelikof Strait April 24-25, and came ashore in Hallo Bay and Katmai Bay along the Alaska Peninsula April 29-30. By May 3, minor quantities of oil were reported as far southwest as

Environ. Sci. Technol., Vol. 28, No. 13, 1994

Chignik. In late April, floating oil in PWS was reduced mostly to surface sheens, except in close proximity to heavily oiled shorelines, where local winds and tides continued to lift the oil from beaches and shift it to nearby shorelines. By May 1, the more fluid oil fractions had seeped into c o a r s e - t e x t u r e d (cobble) b e a c h e s , and surficial oil was mostly mousse with relatively high viscosity and specific gravity and sticky surfaces, such that it adhered to shoreline surfaces and no longer was refloated readily by tidal, wave, or wind action. As of May 1, the OSSM estimated that approximately 4 1 % of the spilled oil was beached in PWS (north of latitude 59.95 °N) and 5.2% was beached on the Kenai P e n i n s u l a (east of l o n g i t u d e 152 °W). About 1.8% of the spilled oil had floated past Cape Douglas into the Shelikof Straits (where much of it had already beached), while another 2% remained floating in the Kenai sector. Part of the estimated 2% that remained floating as of May 1 was no doubt beached subsequently in Shelikof Strait.

The amount of spilled oil ultimately beached in the Kenai area probably lies between 5% and 7% of the total, and in the Shelikof Strait area between 2% and 4%. The formation of mousse, however, increases the effective volume of the floating oil by about three times, and the apparent volume in these downstream sectors of the spill trajectory was exaggerated relative to the proportion of oil that actually reached there. The OSSM estimates for the initial beaching of the floating oil in PWS and the GOA are reflected in Figure 1. Evaporation The primary factors controlling evaporation of oil from a floating slick or from the water column are the composition of the oil, the area and thickness of the slick, temperature, and wind speed (15, 16). Based on a distillation fraction, or "pseudo-component" approach (14, 15, 17), an o i l - w e a t h e r i n g model (OWM) was used (17, 18) to estimate the rates and amounts of evaporative and dispersive losses from the oil slick. Distillation fractions up to 77-C11-13 alkanes, C5-6 benzenes, and methyl naphthalenes ( ~ 20% of Prudhoe Bay crude oil) are most likely to evaporate under environmental conditions, whereas those containing J7-C14-16 alkanes, C3-substituted naphthalenes, acenaphthene, and below effectively represent a theoretical maximum ( ~ 30%) that might evaporate in the absence of competing processes (dispersion, skimming, and biodégradation). Merging predictions from the OWM runs for an 8-knot wind during the first three days and a 20-knot wind during Days 4-10 produced an asymptote of about 0.20 (Days 50—60) for the fraction evaporated (Figure 1). Lower than previous estimates (18, 19), this estimate for total evaporation is consistent with floating-oil composition a month after the spill (18) and with losses of significant portions of relatively fresh oil to skimming and dispersion. Distribution of hydrocarbons in air The oil slick remained fairly compact for the first2 2.5 days, spreading over ~ 300 km and resembling a point source for evaporated constituents. The consistent NE wind carried these atmospheric components on a trajectory (with a widening track as the slick spread) that passed over Naked Island, Eleanor Island,

and Herring Bay on northern Knight Island (20). Maximum concentrations of benzene, toluene, and octane in the air over the slick's center probably occurred within one hour of spillage (20, 21). With an initial concentration of 3.0 mg/g in fresh Prudhoe Bay crude oil (22), the maximum concentration of benzene in air would have been about 9 ppmv, accounting for approximately 5% of the constituents within a similar volatility range. After Day 3, the slick was spread extensively around the islands of PWS and was seeping into coarse cobble beaches. Atmospheric concentrations were greatly reduced as a result of the combined effects of this prior dispersion, reduced volatility, and high winds. Once evaporated, petroleum hydrocarbons rapid oxidize to photolysis p r o d u c t s . Monoaromatics, along with indan, naphthalene, and substituted naphthalenes, can be assigned a mean half-life (t1/2) in air of ~ 1 day, compared to ~ 2 days for biphenyl, acenaphthene, fluorene, phenanthrene, and anthracene and ~ 7 days for the 4- and 5-ringed polycyclic aromatic hydrocarbons (PAHs) (23). At these rates, monoaromatic and n a p h t h a l e n i c compounds were 90% degraded three to four days after they evaporated, and 99% degraded within a week (Figure 1). Recovery or destruction of floating oil On March 25, a small amount of oil was combusted about 10 km southwest of Bligh Island (24). Lightly emulsified oil (estimated at 20—30% water) was concentrated and ignited within a section of floating Fire Boom towed between two boats. The estimated volume consumed was in the range of 15-25 χ 10 3 gal, or only 0.14-0.23% of the original spill volume (25). For several weeks after the spill, floating oil was recovered by skim­ mers operating in PWS, and the re­ covered oil—water emulsion was transported to Seattle or to Exxon's Baytown refinery for processing, oil recovery, and waste water treatment (26). Recovered primarily during the first month (1), 65,000 bbl of oilwater emulsion were ultimately skimmed, corresponding to 18—22 χ 10 3 bbl of spilled oil (25). The mass b a l a n c e (Figure 1) depicts the amount recovered at 8.3% of the original spilled oil (= 65,000 bbl @ 67% water); the probable range is 7-10%.

Dispersion and dissolution Appreciable quantities of oil can be dispersed into the water column through the action of turbulence at the surface (17, 27). Larger blobs of oil rise initially to the surface, and only smaller droplets remain finely dispersed in the water column. As water content and specific gravity rise, dispersed particles of mousse remain suspended in the water col­ umn for longer periods and are sub­ ject to the action of local currents and eddy diffusion. The primary component of dispersion is approx­ imately proportional to the square of wind velocity, which affects the depth to which oil is driven by wave action (27). Under non-wavebreaking conditions, dispersion oc­ curs at a much lower rate. Disper­ sion algorithms (27) were adapted into the NOAA Oil Weathering Model (OWM) and validated with experimental data from wave tanks (10, 17). The OWM was run using 20-knot conditions during Days 4-10 and 8-knot wind conditions for the first three days and for the period after Day 10, producing an asymptote of ~ 2 3 % of total spill mass for dis­ persed oil at about 50 days, with only ~ 3.5% being dispersed during the first 72 h (Figure 1). Much of this dispersion occurred inside of PWS before the slick began to exit through Montague Strait. Some dis­ persed oil was entrained in coastal circulation patterns and remained in PWS longer than the main front of the slick. However, a substantial fraction of the dispersion occurred in Montague Strait (and the adjoin­ ing GOA), and this oil was exiting the Sound at about the time (March 31—April 1) that measurements of oil in the water column began in PWS. Modeled estimates for total dis­ persed oil during March 27—30 are slightly higher but still reasonably consistent with the concentrations of petroleum hydrocarbons (PHC) measured (28-30) in PWS a few days later (Table 1). Total PHC is in the expected range of 67 times (31) the maximum concentrations of to­ tal PAH measured during March 3 1 April 4, assuming uniform disper­ sion to depths of 10 m over the spill area. Hydrocarbons were probably more highly concentrated and more deeply dispersed near the slick front as it departed PWS but would have been missed by the earliest sampling efforts. Also, water sam-

Environ. Sci. Technol., Vol. 28, No. 13, 1994 563 A

TABLE 1

Concentrations of dispersed colloidal and/or dissolved oil in the water column of Prince William Sound at different times after the spill, and corresponding fractions (wt %) of the original spill Time period (days) Offshore 2 7 - 3 0 March 31 M a r c h 4 April 14 April4 May Nearshore 31 M a r c h 4 April

Spill area (m2) (or volume)

Petroleum component

Concentration (pg/L) ( ~ ppb)

Fraction of spilled oil (wt %)

10x108 2x1096

PHC Total PAH PHC° Total PAH PHC C

800a 1-5 67-335 0.1 1-6

23 0.056-0.28 4-19 0.0056 0.056-0.34

2x10

9t>

Reference

28 28

7x107(m3)d

VOAe 1.5 0.0003 29,30 Total PAH 4 0.0008 28 PHC 80-240 0.016-0.040 References indicate measured concentrations in the ranges indicated. a Theoretical concentration from 23% dispersed fraction (NOAA model): equivalent to 12.2 pg PAH/L with uniform dispersion (by 20-25 knot winds) to 10-m depth over effective spill area. "c Effective spill area as of 2 April, 1989: PWS and adjacent Gulf of Alaska. Mass fractions estimated from measured values, assuming uniform dispersion to 10-m depth over effective spill area " Mass fractions estimated as dissolved uniformly to 5-m depth in a 100-m wide band off heavily (75.6 km) and moderately (64.4 km) oiled shorelines in PWS. 8 VOA [volatile organic analytes (29, 30)}.

pies containing mousse particles were usually not included in reported results, and light aromatic hydrocarbons and normal alkanes typically undergo photolysis and degradation in the water column with t 1/2 = 1-3 weeks (23). These factors all contribute to lower measurements of dispersed amounts relative to modeled estimates. The dispersion scenario includes a second component, which accounts for the cumulative dispersion above 23% in Figure 1 and for which there is no direct quantitative estimate. After initial beaching, oil was dispersed into the water column through wave action, highpressure shoreline cleanup activities, and w i n t e r storms. This shoreline dispersion was estimated to remove ~ 35% of the beached oil in PWS ( - 1 5 % of the total spill) over the 3-year period after the spill, with about 2/3 of the total in the first summer and winter season. Along with other processes affecting the beached oil (biodégradation and erosion), this estimate was consistent with the overall progression of shoreline cleansing documented by shoreline assessment teams. Such dispersion was well documented through analyses of elevated hydrocarbon levels in nearshore waters during the summer and fall of 1989 [28-30, 32) and by photographs showing sometimes substantial plumes of suspended sediments flowing downstream from shoreline cleanup activities during 1989 (33). Continued dispersion of oil from beaches was also demonstrated by the persistence 564 A

into 1991 of oil bioaccumulation in caged mussels deployed at stations in PWS (31) and by the persistence of elevated aromatic metabolites in the bile of fishes (34). This dispersion and resultant shoreline cleansing may have been e n h a n c e d through the process of clay—oil flocculation (35). Photolysis and biodégradation in the water column During advection in Alaskan coastal currents, finely dispersed oil would undergo rapid biodégradation without significant limitation caused by oxygen, nitrogen, or phosphorus. Direct measurements of biodégradation, however, are very limited. About 12 days after the spill, toluene biodégradation potential was markedly elevated in water samples taken in coastal waters near Knight Island and in open GOA waters (90% in offshore sediments and dispersed).

GOA (Figure 1) was represented by the same rate function used for PWS. Shoreline dispersion and erosional transport to subtidal sediments were not distinguished from one other, but occurred in the GOA almost exclusively as a result of natural processes. Summary: Mass balance for the spill The foregoing overview of field observations, data, model outputs, and theoretical considerations underlies our provisional mass balance; greater detail is found in our original report (4). In Figure 3, we have recombined the components (removing the geographical distinctions in Figure 2) to simplify the summary mass balance. Estimated

Environ. Sci. Technol.. Vol. 28, No. 13, 1994

Estimate

ranges are given in Table 2 for the cumulative fractions lost to, or remaining in, the various compartments as of October 1992. In summary, the energetic environmental conditions in PWS and the extensive cleanup activities led to wide dispersion of the Exxon Valdez oil, which simultaneously underwent biodégradation and photooxidation. Although some more refractory residuals of the petroleum (e.g., high molecular weight PAH, resins, and asphaltenes) persist, many of these constituents are not readily distinguishable from other petroleum sources and naturally occurring hydrocarbon residues (e.g., seeps, combustion produ c t s , and biogenic organic materials).

W e e s t i m a t e t h a t ~ 2 0 % of t h e s p i l l e d oil e v a p o r a t e d a n d u n d e r w e n t photolysis in t h e a t m o s p h e r e ; ~ 5 0 % biodegraded either in-situ o n b e a c h e s o r in t h e w a t e r c o l u m n ; ~ 1 4 % w a s r e c o v e r e d or d i s p o s e d ; < 1 % r e m a i n e d in t h e w a t e r c o l u m n ( e x c e p t as b i o d é g r a d a t i o n p r o d ucts); ~ 2 % r e m a i n e d on intertidal shorelines (with a very large proport i o n of t h i s as h i g h l y w e a t h e r e d , b i o logically inert r e s i d u a l s ) ; a n d ~ 1 3 % r e m a i n e d in s u b t i d a l s e d i m e n t s , m o s t l y in t h e G O A a n d a g a i n m o s t l y as h i g h l y w e a t h e r e d r e s i d u a l s . A l t h o u g h m a n y of t h e p r o c e s s e s identified here could not be quantified d i r e c t l y u n d e r t h e c o n d i t i o n s a p p l i c a b l e to the spill, their occurrence was well documented, and w e believe that our estimates prov i d e a r e a s o n a b l e a p p r o x i m a t i o n of t h e o v e r a l l f a t e of t h e o i l s p i l l e d from t h e Exxon Valdez. Acknowledgments T h i s work r e p r e s e n t s a c o l l a b o r a t i o n and integration of many projects carried out u n d e r the State/Federal Natural Resources Damage Assessment for the Exxon Valdez oil spill, receiving direct support from projects Air/Water 4, Air/ Water 6, a n d S u b t i d a l 4. Bernie Gottholm and Adriana Cantillo of NOAA/ ORCA/CMBAD provided invaluable graphics assistance. References (1)

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National Response Team. " T h e EXXON VALDEZ Oil Spill: A Report to the President"; U.S. Department of Transportation and U.S. Environmental Protection Agency: Washington, DC, May 1989. Kelso, D. D.; Kendziorek, M. Environ. Sci. Technol. 1991, 25, 16-23.

Douglas A. Wolfe has been engaged in oil spill studies since 1975 and is head of the Bioeffects Assessment Branch, National Ocean Service, NOAA, in Silver Spring, MD. He received his Ph.D. in physiological chemistry from Ohio State University. He and all coauthors of this paper became involved in 1989 in projects dealing with the fate of the Exxon Valdez oil, conducted under the joint State of Alaska-Federal Natural Resources Damage Assessment for the spill.

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Maki, A. W. Environ. Sci. Technol. 1991, 25, 24-29. (4) Wolfe, D. A. et al. "Fate and Toxicity of Spilled Oil from the Exxon Valdez"; Final Report to State-Federal Trustees, Natural Resources Damage Assessment Subtidal Project No. 4; NOAA/ORCA: Silver Spring, MD, 1993. (5) National Academy of Sciences. Oil in the Sea: Inputs, Fates, and Effects; National Academy Press: Washington, DC, 1985. (6) Clark, R. C , Jr.; MacLeod, W. D„ Jr. In Effects of Petroleum on Arctic and Subarctic Marine Environments and Organisms. Vol. 1. Nature and Fate of Petroleum; Malins, D. C Ed.; Academic Press: New York, 1977; pp. 9 1 223. (7) Wolfe, D. A. In Wastes in the Ocean, Volume 4. Energy Wastes in the Ocean; Duedall, I. W. et al., Eds.; Wiley: New York, 1985; pp. 45-93. (8) Wolfe, D. A. In Fate and Effects of Sediment-bound Chemicals in Aquatic Systems; Dickson, K. L. et al., Eds.; Pergamon Press: Oxford, England, 1987; pp. 299-316. (9) Jordan, R. E.; Payne, J. R. Fate and Weathering of Petroleum Spills in the Marine Environment; Ann Arbor Science P u b l i s h e r s : Ann Arbor, Ml, 1980. (10) Payne, J. R.; Phillips, C. R. Petroleum Spills in the Marine Environment: The Chemistry and Formation of Water-in-Oil Emulsions and Tar Balls; Lewis Publishers: Chelsea, MI, 1985. (11) Trustee Council. "State/Federal Natural Resource Damage Assessment Plan for the Exxon Valdez Oil Spill: Public Review Draft"; Alaska Department of Environmental Conservation: Juneau, AK, 1989. (12) Gait, J. A. et al. Environ. Sci. Technol. 1991, 25, 202-09. (13) Gait, J. A. et al. In Proc. Internatl. Oil Spill Conf., Publ. No. 4529; American Petroleum Institute: Washington, DC, 1991; pp. 629-34. (14) Payne, J. R. et al. In Proc. 1983 Oil Spill Conf, Publ. No. 4356; American Petroleum Institute: Washington, DC, 1983; pp. 423-34. (15) Mackay, D. et al. In Proc. 1983 Oil Spill Conf, Publ. No. 4356, American Petroleum Institute: Washington, DC, 1983; pp. 331-37. (16) Stiver, W. et al. Environ. Sci. Technol. 1989, 23, 101-05. (17) Payne, J. R. et al. In Environmental Assessment of the Alaska Outer Continental Shelf; OCSEAP Final Reports 21 and 22; NOAA: Anchorage, AK, 1984. (18) Payne, J. R. et al. In Proc. Internatl. Oil Spill Conf., Publ. No. 4529, American Petroleum Institute: Washington, DC, 1991; pp. 642-54. (19) Koons, C. B.; Jahns, H. O. Mar. Technol. J. 1993, 26, 61-69. (20) Hanna, S. et al. "Air Quality Impact.s from VOC E m i s s i o n s " ; Report to Alaska Department of Environmental Conservation (Contract No. 18-401890). Sigma Research Corp.: Concord, MA, 1991. (21) Hanna, S. R.; Drivas, P. J. /. Air Waste Mgmt. Assoc. 1993, 43. 298-30.

(22) Clark, R. C , Jr.; Brown, D. W. In Effects of Petroleum on Arctic and Subarctic Marine Environments and Organisms. Vol. 1. Nature and Fate of Petroleum; Malins, D. C , Ed.; Academic Press: New York, 1977, 1-89. (23) Mackay, D. et al. Illustrated Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals; Lewis Publishers: Boca Raton, FL, 1992; Vols. 1 and 2. (24) Allen, A. A. In Proc. Internatl. Oil Spill Conf, Publ. No. 4529, American Petroleum Institute: Washington, DC, 1991; pp. 213-16. (25) Alaska Department of Environmental Conservation. "Exxon Valdez Oil Spill Update. Fact Sheet, March 23, 1992"; Exxon Valdez Oil Spill Response Center Public Information Office: Anchorage, AK, 1992. (26) Carpenter, A. D. et al. In Proc. Internatl. Oil Spill Conf; Publ. No. 4529, American Petroleum Institute: Washington, DC, 1991; pp. 205-11. (27) Mackay, D. et al. "Oil Spill Processes and Models"; Report to Research & Development Division., Environment Emergency Branch, Environmental Impact Control Directorate, Environmental Protection Service, Environment Canada: Ottawa, Ontario, 1980. (28) Short, J. W.; Rounds, P. In Exxon Valdez Oil Spill Symposium; Feb. 2—5, 1993, Anchorage, AK; Abstracts, pp. 57-59. (29) Neff, ]. M. "Water Quality in Prince William Sound and the Gulf of Alask a - M a r c h , 1 9 9 1 " ; Special Report, Arthur D. Little Corp.: Cambridge, MA, 1991. (30) Neff, J. M. Presented at 14th Annual Arctic & Marine Oilspill Program Technology Seminar, Vancouver, BC, June 12-21, 1991. (31) Short, J. W.; Rounds, P. In Exxon Valdez Oil Spill Symposium, Feb. 2—5, 1993, Anchorage, AK; Abstracts, pp. 186-87. (32) Neff, J. M. et al. In Oil Spills: Management and Legislative Implications; S p a u l d i n g , M. L.; Reed, M. Eds.; American Society of Civil Engineers: New York, 1990, 426-43. (33) Mearns, A. J. In Exxon Valdez Oil Spill Symposium; Feb. 2-5,1993, Anchorage, AK; Abstracts, pp. 83-86. (34) Collier, T. K. et al. In Exxon Valdez Oil Spill Symposium; Feb. 2-5, 1993, Anchorage, AK; Abstracts, pp. 2 3 5 38. (35) Bragg, J. R.; Yang, S. H. In "Clay-Oil Flocculation and its Effect on the Rate of Natural Cleansing in Prince William Sound Following the Exxon Valdez Oil Spill"; Wells, P. G. et al., Eds. ASTM STP1219; American Society for Testing and Materials: Philadelphia, PA, 1993. (36) Button, D. K. et al. Appl. Environ. Microbiol. 1992, 5«, 243-51. (37) Braddock, J. F. et al. "Final Report to Alaska Department of Environmental Conservation from the Institute of Arctic Biology & Water Research Center"; University of Alaska: Fairbanks, 1992. (38) Leahy, J. G.; Colwell, R. R. Microbiol. Rev. 1990, 54, 305-15. (39) Rontani, J. F', et al. Chemosphere

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1985, 14, 1413-22. (40) K v e n v o l d e n , Κ. Α.; R a p p , J. B.; Hostettler, F. D. "Tracking Hydrocar­ bons from the Exxon Valdez Oil Spill in Beach, Shallow-Water, and DeepWater Sediment of Prince William Sound, Alaska"; In Carlson, P. R., Ed.; Open-File Report 91-631; U.S. Geo­ logical Survey: Menlo Park, CA, 1991; pp. 69-98. (41) Carlson, P. R.; Kvenvolden, K. A. In Exxon Valdez Oil Spill Symposium; Feb. 2-5, 1993, Anchorage, AK; Ab­ stracts, pp. 43-45. (42) O'Clair, C. E. et al. In Êxxon Valdez Oil Spill Symposium; Feb. 2-5, 1993, Anchorage, AK; Abstracts, pp. 55—56. (43) Page, D. S. et al. In "Identification of Hydrocarbon Sources in the Benthic Sediments of Prince William Sound and the Gulf of Alaska Following the Exxon Valdez Oil Spill"; P. G. Wells et al., Eds.; ASTM STP1219; American Society for Testing and Materials: Philadelphia, PA, 1993. (44) Jahns, H. O. et al. In Proc. Internatl. Oil Spill Conf.; Publ. No. 4529, American Petroleum Institute: Washington, DC, 1991; pp. 167-76. (45) Michel, J. et al. In Proc. Internatl. Oil Spill Conf.; Publ. No. 4529, American Petroleum Institute: Washington, DC, 1991; pp. 181-87. (46) Roberts, P. O. et al. In Exxon Valdez Oil Spill Symposium, Feb. 2 - 5 , 1993,

Anchorage, AK. Abstracts, pp. 46-47. (47) Babcock, M. et al. In Exxon Valdez Oil Spill Symposium, Feb. 2-5, 1993, Anchorage, AK. Abstracts, pp. 1 8 4 85. (48) Chianelli, R. R. et al. In Proc. Internatl. Oil Spill Conf.; Publ. No. 4529, American Petroleum Institute: Washington, DC, 1991, 549-58. (49) Pritchard, P. H.; Costa, C. F. Environ. Sci. Technol. 1991, 25, 372-79. (50) Bragg, J. R. et al. "Column Flow Studies of Bioremediation in Prince William Sound"; Report, Exxon Production Research Co.: Houston, TX, 1990. (51) Tabak, H. H. et al. In Proc. Internatl. Oil Spill Conf.; Publ. No. 4529, American Petroleum Institute: Washington, DC, 1991; pp. 583-90. (52) Bragg, J. R. et al. In Proc. 1993 Oil Spill Conf, Publ. No. 4580, American Petroleum Institute: Washington, DC, 1993; pp. 435-47. (53) Lindstrom, J. E. et al. Appl. Environ. Microbiol. 1991, 57, 2514-22. (54) Prince, R. C. et al. "Assessing rates of oil biodégradation in Prince William Sound" (abstract). American Society of Microbiology Conference on Biotechnology, June 2 7-30, 1991, New York. (55) Boehm, P. D. et al. In "Shoreline Ecology P r o g r a m for P r i n c e W i l l i a m Sound, Alaska, Following the Exxon Valdez Oil Spill: Part 2—Chemistry

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and Toxicology"; P. G. Wells et al., Eds. ASTM STP1219, American Society for Testing and Materials: Philadelphia, PA, 1994. Sale, D. M. et al. In Exxon Valdez Oil Spill Symposium; Feb. 2 - 5 , 1993, Anchorage, AK; Abstracts, pp. 64-67. Michel, J.; Hayes, M. O. Report No. HMRB 91-2 to NOAA Hazardous Materials Response Branch, Seattle, WA; Research Planning, Inc.: Columbia, SC, 1991. Rapp, J. B. et al. In "Comparison of Exxon Valdez Oil with Extractiable Material from Deep-Water Bottom Sediment in Prince William Sound and the Gulf of Alaska"; Carlson, P. R.; Reimnitz, E., Eds.; Open-File Report 90-39-B; U.S. Geological Survey: Menlo Park, CA, 1990. Michel, J.; Hayes, M. O. "Evaluation of the Condition of Prince William SoundShorelines Following the Exxon Valdez Oil Spill and Subse q u e n t S h o r e l i n e T r e a t m e n t . Vol. 1—1991 Geomorphological Shoreline Monitoring Survey"; NOAA Tech. Memo. NOS ORCA67. NOAA/ORCA: Seattle WA, 1992. Gundlach, E. et al. In Proc. Internatl. Oil Spill Conf; Publ. No. 4529, American Petroleum Institute: Washington, DC, 1991; pp. 519-29.

Environ. Sci. Technol., Vol. 28, No. 13, 1994

For more information please contact: ICT-VII Management Staff The Wellington Group 4707 College Boulevard, Suite 213 Leawood, KS 66211 Telephone: (913)345-1990 Fax: (913)345-0893 REFER TO KEY NO. 3