LONG-TERM WEATHERING OF OIL IN SOFT INTERTIDAL SEDIMENTS

David S. Page, Judith C. Foster, Paulette M. Fickett Bowdoin College Hydrocarbon Research Center

Brunswick, Maine 04011 Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1989/1/401/1741600/2169-3358-1989-1-401.pdf by guest on 27 September 2021 Edward S. Gilfillan Bowdoin College Marine Research Laboratory Brunswick, Maine 04011

ABSTRACT: Samples of sediment were taken at intervals between 1979 were expected. It was therefore necessary to select a reference area and 1986 from soft sediment locations in the Aber Benoit, an estuary with features as similar as possible to the low-energy mudflat sites to heavily impacted by the Amoco Cadiz of 1978, and from a permit the definition of an end-point for oil weathering. The area comparable reference site outside the spill zone. Each sample was chosen was the Bay of Kerogan in the Odet River, south of the spill analyzed for aliphatic hydrocarbons by capillary gas chromatography. zone and 5 km downstream from the city of Quimper. This location The data demonstrate the progressive weathering of the Amoco Cadiz was remarkably similar in appearance to the Loc Majan cove (Site 2, oil resulting in an assemblage of biogenic hydrocarbons similar to the Table 1). reference site by 1986 at all but the most heavily impacted locations. The weathering of Amoco Cadiz oil was monitored by various The data indicate that any residues of weathered Amoco Cadiz oil pres- groups at selected locations between 1978 and 1981.5 During the six- ent in 1985-86 were in the final stages of degradation. to 12-month period after the spill, the stranded oil in the Aber Benoit underwent processes that altered the distribution of oil within the aber and the distribution of hydrocarbons in the oil itself. In April, 1978, one month after the spill, Allen, et al.1 found most of the oil distributed on the more exposed locations that received the initial On March 16, 1978, the Amoco Cadiz grounded off the impact. Within 12 months after the spill, Morel15 and Morel and coast of , France, spilling her cargo of 221,000 tons of light Courtot16 demonstrated that a large proportion of hy- 13 Middle Eastern crude oil over the next 15 days. About 320 km of drocarbons was moving around the interior of the aber associated 3 coastline was affected to varying degrees. While at sea, the oil under- with suspended particulate matter. The result was the accumulation 2 went extensive evaporative and biodegradative loss so that the petro- of particulate-associated hydrocarbons in low-energy depositional leum that stranded had changed in character from the original cargo areas.15 For these locations, total hydrocarbon concentrations were oil. Of the 62,000 tons of oil estimated to be on the shore at the end observed to remain static or actually increase between 1978 and 1979, of March, 1978, only 9,200 tons was estimated to be remaining a even though extensive biodegradation of the petroleum residues was 7 month later. The loss was due to cleanup activities and the extensive observed.15,16 Similar observations were made for the behavior of oil 11 biodegradation of the stranded oil. in the nearby Aber Wrac'h during the first six to 12 months after the The Aber Benoit, an estuary about 10 km east from the site of the spiU 4,5,6,14,21 wreck, was heavily affected. Its east-west orientation, the westerly The present study was begun in 1979 to follow the actual changes winds during the initial weeks of the spill, and the 6 to 9 m tides in this 1 in petroleum residues in soft-sediment environments over time. The area forced in large quantities of oil. Figure 1 shows the Aber Benoit authors conducted sampling trips to the Amoco Cadiz impact zone in and a portion of the Aber W'rach, along with the study sites described June and December, 1979; December 1980; July 1984; October, 1985, in Table 1. The Aber Benoit is approximately 10 km long and 1 km and March 1986. The point of reference for the original spilled oil wide at the mouth. The freshwater input to the aber is less than 18 15 was a mousse sample taken from a collection pit on the beach at St. percent of its total volume. Transport of suspended sediment within Michel en Greve in June, 1978. While both aliphatic and aromatic the aber is mainly the result of tidal current-driven resuspension and 115 hydrocarbon fractions were analyzed by capillary gas chromatog- transport. As a result, the Aber Benoit has extensive mudbanks raphy, the course of oil weathering was documented in terms of consisting of fine reduced sediment in low-energy areas. These soft molecular markers in the aliphatic fraction. The weathering of the sediment environments have been ranked as being highly vulnerable 10 Amoco Cadiz petroleum residues in sediments has been characterized to oil spills where oil may persist for more than 10 years. by the loss of n-alkanes and 1- and 2-ring aromatics within 12 months The land around the Aber Benoit is primarily agricultural and rural at most locations. Isoprenoids, long chain alkanes, pentacyclic triter- residential. Small commercial and pleasure craft were moored 1 to 2 panes, unresolved complex material, and aromatics with three or km in from the mouth of the aber. There were also parks at more rings were observed to degrade more slowly.511 locations in the intertidal zone in the same area. Septic drainages from individual dwellings and several small towns and villages resulted in high levels of fecal coliform bacteria in the water throughout the aber.9 The many small streams draining into the aber gave visual Materials and methods evidence of organic and nutrient enrichment. Because of these various inputs of non-petroleum organic matter, Intertidal sediment samples were taken in the field using solvent- relatively high background levels of sediment biogenic hydrocarbons cleaned sampling gear. Ordinarily a 6-cm diameter metal coring de-

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Figure 1. Map of the Aber Benoit showing the locations of the sampling sites—The inset shows the relative locations of the study areas and the reference area.

Table 1. Locations of sampling sites within the Aber Benoit and the Odet River reference area. The numbered Aber Benoit sites correspond to those shown in Figure 1.

Aber Benoit sites and a soft mud middle and lower tide zone broken into small channels by land runoff. In 1985, traces of oily sheen were St. Pabu, Porz ar Vilin area, 30 in upstream from an oyster observed when digging in the soft mud at various locations in park. The area is a mudbank accessible by foot. The samples this area. The sample was taken in an area of soft mud were taken from the same area of soft sediment at the low tide exhibiting an oily sheen when disturbed. line. In 1979, heavy oil sheen was produced when the sediment Lannilis, 200 meters downstream from the D28 Bridge. This was disturbed. By 1986, there was no visible evidence of oil. station consisted of sandy mud at the mid tide zone that showed St. Pabu, western side of Loc Majan cove. This is a large visual evidence, even in 1979, of extensive bioturbation by depositional area in which fine sediment and associated organic polychaetes. In 1979, the reduced sediment layer began almost matter accumulates. The soft mud banks on the western side at the surface and showed an oily irridescence when disturbed. are more than 2 m deep and are impassable without flotation By 1984, the dark colored reduced layer began at a depth of aid. In 1979 and 1980, the soft mud along the western shore was 4 cm and no visual traces of oil could be seen. hydrophobic and exuded oil sheen when disturbed. No evidence of foraging by seabirds was observed. In 1985 and 1986, the mud surface appeared normal and only scattered traces of oil sheen could be observed in a small fraction of holes dug Reference area throughout the mudflat. There was extensive visual evidence of L'Odet River, Bay of Kerogan. This is an embayment in a tidal seabird foraging on the mud surface. The samples taken in river similar in shape and situation to Loc Majan cove. It acts as a 1980, 1984, and 1985 were taken at a location 0.5 meter into the trap for fine grain sediments and is characterized by extensive mudbank from the break in the rocky upper tide zone. The banks of deep, soft, reduced mud. 1986 sites A and B were taken 10 m and 20 m out onto the A. Depositional area at the head of the south branch of bay; soft mudflat from the 1985 site, respectively. The 1986 samples were sediment from a small feeder creek bank west of main stream stratified (0-4 cm and 4-20 cm) cores. B. Depositional area at head of south branch of bay. Soft Lannilis, Lothonou Cove area. This is a small cove acting as a sediment 1 meter from the bank of the main creek near the trap for fine sediment, characterized by a rocky upper tide zone 'Mowlin de Kerdour'

vice was used to obtain a sample of the top 10-cm layer. In some cases, For consolidated sediment samples, a 50-100 g wet aliquot was styrofoam walking devices had to be used to permit safe access to placed in a tared thimble and extracted in a Soxhelet extractor for 24 very soft sediment areas. Each sample was placed in a solvent-rinsed hrs with methanol to remove water from the sample, followed by a Mason-type jar leaving no air space. The jars were sealed using foil- 24 hr extraction with CH2C12. Unconsolidated semi-liquid sediment lined lids, returned to the laboratory in Brunswick, Maine, and frozen samples were first mixed with an aliquot of a cellulose filter-aid to at -20° C until analyzed. promote uniform extraction. The methanol extract was partitioned FATE AND EFFECTS 403 against pentane. The pentane and methylene chloride extracts were comparable with the reference site values of 7.7 and 62.4, except for dried, combined, evaporated to a residue, and weighed on a micro- sites 2A and 3. balance to obtain a total extractable oil and grease (O&G) weight. All Gas chromatographic results. The gas chromatographic data for the or part of the total extractable residue was dissolved in hexane and reference samples provide an endpoint for the progressive changes further analyzed by liquid and capillary gas chromatography as de- in hydrocarbon distribution that take place during weathering. Figure scribed in detail elsewhere.18 2A shows the aliphatic hydrocarbon distribution in the reference sediment at site A. The dominant components are the odd-chain n-alkanes having chain lengths between 23 and 31 carbons, a charac- teristic pattern for hydrocarbon inputs derived from terrestrial plant Results and discussion 1219,20 12 material. The n-Cn alkane peak is of bacterial origin. The minor peaks between n-C2g and n-Cw and between n-Cjo and Quantitative results. Table 2 summarizes the gravimetric results for w-C3i correspond to pentacyclic triterpanes, persistent markers of the sediment samples. While these data alone do not reflect changes weathered petroleum. The other chromatograms in Figure 2 (B, C, in petroleum due to weathering, the data do show that changes did and D) show the aliphatic fraction hydrocarbons from 1986 samples occur. Because hydrocarbons are ubiquitous in marine sediments, taken in the Aber Benoit. The hydrocarbon distributions are virtually defining a zero endpoint for petroleum weathering in sediments identical with those of the reference samples with a greater contribu- Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1989/1/401/1741600/2169-3358-1989-1-401.pdf by guest on 27 September 2021 would be inappropriate. The data for the reference site samples show tion of n-Cn (bacterial origin) consistent with the high levels of that for the soft-sediment environments studied here, baseline hydro- coliform bacteria measured in the Aber Benoit.9 This means that the carbon concentrations can be more than 600 ppm. In 1986, the surface Aber Benoit sampling sites represented in Figure 2 have returned to sediments at all Aber Benoit sites, except sites 2A and 3, had total a state comparable with a reference site outside the spill zone. Any hydrocarbon concentrations in the range of 377 to 757 ppm. This was petrogenic contribution from the Amoco Cadiz at these sites is indis- similar to the reference sample values of 594 and 661 ppm. For those tinguishable from the background of chronic petroleum inputs charac- sites studied over the longest time (sites 1 and 4), the data reflect the teristic of an coastal location.18 progressive loss of petroleum hydrocarbons from the sediments. The The compositional changes that take place during weathering for rapid decrease in total hydrocarbons at site 1 between 1979 and 1980 Amoco Cadiz oil in a variety of locations for the period 1978-1981 was due to the removal of contaminated sediment as part of a resto- have been well documented.4,511'21 The results in these references ration program for nearby oyster parks. This demonstrates the im- correspond closely to the data shown in Figures 3 and 4. Figure 3 portance of cleanup procedures in accelerating the long-term rate of shows the long-term changes taking place at site 1. In December 1979 recovery.8 Physical removal of sediment was not observed at the other (Figure 3B), the gas chromatographic data show that the n-alkanes study locations. had been completely biodegraded but that the isoprenoid peaks cor- For all impact zone sites, the proportion of total hydrocarbons responding to pristane, phytane, and 3 lower boiling isoprenoids are (TOTHC) in the total lipid (O&G) extract decreased between 1978 well-resolved. In 1979 this location was heavily oil-impacted (22,550 and 1986. The ratio, O&G/TOTHC, in Table 2 increases in value as ppm total hydrocarbons). A 1979 O&G/TOHC value of 1.3 (Table 2) the proportion of hydrocarbons in the lipid-soluble material decreases indicates a poor degree of weathering. By 1986, the aliphatic hydro- due to biodegradation of the petroleum residues present. For the 1978 carbons present at this location were indistinguishable from those Amoco Cadiz reference mousse, the value of O&G/TOTHC was 1.2, present at the reference site (Figure 3C and 3D). The 1986 O&G/ reflecting a high proportion of hydrocarbons in the total lipid extract. TOTHC value of 6.5 is close to the value of 7.7 for reference site B. By 1986, the O&G/TOTHC values ranged from 6.5 to 628 and were Figure 4 shows the progressive changes in the aliphatic hydrocarbon

Table 2. Gravimetric results for hydrocarbon analyses performed on sediment samples taken from locations in the Aber Benoit and the reference area between 1979 and 1986.,

Layer O&G Aliphatics Aromatics Total HC Location (cm) Date PPm PPm PPm PPm O&G/TOTHC Aber Benoit: Site 1 0-10 12/79 29,800 17,000 5,550 22,550 1.3 0-10 12/80 5,570 2,120 877 3,000 1.8 0-10 3/86 2,140 212 188 400 6.5 Site 2 0-5 12/80 14,500 4,870 2,030 6,900 2.1 0-5 7/84 8,850 2,010 1,960 3,970 2.2 0-10 10/85 12,100 2,770 2,820 5,590 2.2 0-5 3/86A 15,000 2,350 2,160 4,510 3.3 0-5 3/86B 6,316 547 210 757 8.3 5-20 3/86A 3,470 33 97 130 26.6 5-20 3/86B 23,100 16 20 37 628 Site 3 0-10 10/85 4,500 1,110 1,000 2,110 2.1 Site 4 0-10 6/79 6,440 2,440 740 3,180 2.0 0-10 12/79 2,910 761 905 1,670 1.7 0-10 12/80 8,130 2,430 1,150 3,580 2.3 5-10 7/84 2,280 349 247 596 3.8 0-10 3/86 2,460 209 168 377 6.5 L'Odet River Reference Area; Baie de Kerogan Site A 0-5 3/86A 37,000 388 206 594 62.4 SiteB 0-5 3/86B 5,090 493 168 661 7.7 1. The values are given as ppm on a dry sediment weight basis. The quantity O&G/TOTHC is the concentration of total solvent-extractable material divided by the concentration of total hydrocarbons. For those sediments having total extractable material most closely resembling petroleum, the O&G/TOTHC will have a low value. As naturally occurring fats, oils, and waxes make a greater contribution to the total extractable (O&G) value, this ratio will have a larger value and is therefore a semi-quantitative index of weathering. 404 1989 OIL SPILL CONFERENCE Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1989/1/401/1741600/2169-3358-1989-1-401.pdf by guest on 27 September 2021

Figure 4. Aliphatic hydrocarbons in Aber Benoit sediment site 4—Corresponding peaks are aligned vertically; n-alkane peaks and Figure 2. Aliphatic hydrocarbons in Aber Benoit sediments com- phytane (ph) are noted. (A. 1978 Amoco Cadiz reference mousse; B. pared with a reference area sediment—The numbered peaks corre- June 1979; C. July 1984; D. March 1986) spond to the n-alkanes having the same number of carbons. The corresponding peaks of the chromatograms are aligned vertically. (A. Odet River reference area site A; B. Aber Benoit site 2A, 1986, 5-20 cm layer; C. Aber Benoit site 4, 1986; D. Aber Benoit site 1, 1986) served in the field at the less heavily impacted site is consistent with similar observations made by Fusey and Oudot8 in a controlled set of test spills of a product similar to the Amoco Cadiz cargo. Sites 2 and 3 contained much softer sediment than sites 1 and 4. The orientation of the sampling sites and the very fine grain nature of these sediments indicates that these locations are depositional areas for waterborne suspended paniculate matter from other parts of the Aber Benoit. Data published by Morel15 for a location in the same area as site 2 show a decline in surface sediment total hydrocarbon concentrations from a value of 70,800 ppm in November 1978 to 1,260 ppm in August 1979. This was followed by an increase to 6,925 ppm by December 1979. Allowing for intrasite variability in hydrocarbon concentrations, this observation is consistent with the observation15 that a large proportion of petroleum hydrocarbons in the Aber Benoit was adsorbed to suspended particulate matter and was moving around the interior of the aber. At site 2, the western shore of Loc Majan cove appeared to accumulate fine grain sediment to a greater extent than other parts of the cove. In 1980, the soft surface sediments along the low tide margin appeared hydrophobic and readily released an oily film when disturbed. By 1986, few visible traces of petroleum residues remained. At site 2A, 10 m out on the mudflat from the rocky upper shore, traces of highly weathered petroleum remained in the upper 5 cm layer only. This is evident in the elevated total hydro- crabon concentration of 4,510 ppm and the lower O&G/TOTHC value of 3.3. The fact that the total hydrocarbon concentrations at the nearshore locations at site 2 did not change much from 1980 to 1986 indicates that this shore had been continually receiving sediment- associated hydrocarbons from other parts of the aber. That weather- Figure 3. Aliphatic hydrocarbons in Aber Benoit sediment site ing was taking place is shown by the increase in the O&G/TOTHC 1—Corresponding peaks are aligned vertically; n-alkane peaks and values over the same period. Below 5 cm, the hydrocarbon distribu- pristane and phytane are noted. (A. 1978 Amoco Cadiz reference tion is indistinguishable from the reference samples. At site 2B, 20 m mousse; B. December 1979; C. March 1986; D. Reference site B) offshore onto the mudflat, no visible traces of oil were found and the aliphatic hydrocarbons in the surface sediments closely corresponded to those of a reference sample. Site 3, sampled in October 1985, showed the least weathered traces distribution at site 4. By June 1979, the n-alkanes and isoprenoid of petroleum attributable to the Amoco Cadiz spill. The gas chro- hydrocarbons at this site had almost completely biodegraded. The matograms in Figure 5 show the aliphatics from site 3 and those from petrogenic isoprenoid peak corresponding to phytane marked on the reference site B. The emergence of the background aliphatic Figure 4B is small compared with the emerging biogenic n-Q21 and hydrocarbon distribution found in other "recovered" sites in the aber n-C2g peaks. This indicates that the petroleum hydrocarbons present is clearly evident in Figure 5A. Triterpane and sterane peaks charac- at site 4 were more extensively weathered in June 1979 than those at teristic of weathered petroleum are evident in Figure 5A. Finally, the site 1 in December 1979. The concentration of total hydrocarbons at 1985 O&G/TOTHC value of 2.1 for this site is comparable with the site 4 in June 1979 (3,180 ppm) was substantially lower than at site 1 1980 values for sites 1,2, and 4 again indicating incomplete biodegra- in December 1979 (22,500 ppm). The more rapid weathering ob- dation. FATE AND EFFECTS 405

27 I 29 4. Boehm, P. D., D. L. Fiest, and A. Elskus, 1981. Comparative weathering patterns of hydrocarbons from the observed at a variety of coastal environments, in Amoco Cadiz: Consequences d'une Pollution Accidentelle par les Hy- drocarbures; Fates and Effects of the Oil Spill. Centre National Pour L'Exploitation des Oceans, Paris, ppl59-173 5. Boehm, P. D., 1982. The Amoco Cadiz analytical chemistry pro- gram. in NOAA-CNEXO Joint Scientific Commission Report: Ecological Study of the Amoco Cadiz Oil Spill. National Oceanic and Atmospheric Administration, Washington, D.C., pp35-100 6. Calder, J. A. and P. D. Boehm, 1981. The chemistry of Amoco Cadiz oil in the Aber Wrac'h. in Amoco Cadiz: Consequences d'une Pollution Accidentelle par les Hydrocarbures; Fates and Effects of the Oil Spill. Centre National Pour L'Exploitation des Oceans, Paris, ppl59-173 Figure 5. Aliphatic hydrocarbons in Aber Benoit 1986 sediment site 7. Finkelstein, K. and E. R. Gundlach, 1981. Method for estimating Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1989/1/401/1741600/2169-3358-1989-1-401.pdf by guest on 27 September 2021 3 (A) compared with reference site B (B)—Corresponding peaks are spilled oil quantity on the shoreline. Environmental Science and aligned vertically; n-alkane, sterane (s), and pentacyclic triterpane (t) Technology, vl5, pp545-549 peaks are noted. The vertical scale expansion on chromatogram A is 8. Fusey, P. and J. Oudot, 1984. Relative influence of physical twice that of chromatogram B. removal and biodegradation in the depuration of petroleum- contaminated seashore sediments. Marine Pollution Bulletin, vl5, ppl36-141 9. Gilfillan, E. S., D. S. Page, B. Griffin, S. A. Hanson, and J. C. Conclusions Foster, 1987. The use of stepwise multiple regression to associate body burdens of different pollutants with effects on the phys- iology of Crassostrea gigas from the Amoco Cadiz oil spill impact It is possible to define a series of stages for the weathering of zone, in Pollution Physiology of Estuarine Organisms, W. B. petroleum in a heavily affected, confined estuary such as the Aber Vernberg, A. Calabrese, F. P. Thurberg, and F. J. Vernberg, Benoit. After an initial distribution of petroleum on the more exposed 1 eds., University of South Carolina Press, Columbia, South Caro- parts of the estuary, redistribution of sediment-associated petroleum lina, ppl55-169 residues from higher energy to lower energy environments took 10. Gundlach, E. R. and M. O. Hayes, 1978. Vulnerability of coastal place.15 Over a short term, the concentrations of petroleum in deposi- environments to oil spill impacts. Marine Technology Society tional areas receiving sediment-bound petroleum residues can actu- Journal, vl2, pp 18-27 ally appear to increase.15 While these mechanical processes were tak- 11. Gundlach, E. R., P. D. Boehm, M. Marchand, R. M. Atlas, D. ing place, microbial degradation of petroleum components occurred 5 17 M. Ward, and D. A. Wolfe, 1983. The fate of the Amoco Cadiz on a continuous basis. The overall apparent rate of biodegradation oil. Science, v221, ppl22-129 was observed to decrease as the more rapidly biodegraded fractions 12. Han, J., E. D. McCarthy, W. Van Hoeven, M. Calvin, and W. H. became depleted, giving rise to a progressively more refractory mix- Bradley, 1968. A preliminary report on the distribution of ali- ture of substances. phatic hydrocarbons in algae, in bacteria, and in a recent lake The depositional areas in the present study (sites 2, 3, and refer- sediment. Organic Geochemical Studies, II. Proceedings of the ence) had the highest concentrations of total extractable lipid mate- National Academy of Sciences, v59, pp29-33 rial, consistent with their importance as repositories for all forms of 13. Hess, W. N., ed., 1978. The Amoco Cadiz Oil Spill: A Prelim- organic material undergoing transport within the estuary. The abun- inary Scientific Report. National Oceanic and Atmospheric dance of biogenic hydrocarbons in these soft sediments means that Administration—U.S. Environmental Protection Agency. 283pp non-specific methods for analyzing hydrocarbons, such as infrared 14. Marchand, M., 1980. The Amoco Cadiz oil spill, distribution and spectrophotometry, can give misleading results on the extent of oil evolution of hydrocarbon concentrations in seawater and marine weathering. Equally important is the appropriate definition of refer- sediments. Environment International, v4, pp421-429 ence sites. As the results presented here demonstrate, the ultimate 15. Morel, G., 1981. Evolution of Biogenic and Fossil Hydrocarbons endpoint for chemical recovery from an oil spill can be estimated in an Enclosed Site on the North Coast of Finnesterre, the Aber through analyses of sediments from reference sites having character- Benoit, Greatly Disturbed by the Amoco Cadiz Oil Pollution. istics similar to the study area. Doctoral thesis, University of West Brittany, France. 276pp Eight years after the spill, measurable residues of weathered petro- 16. Morel, G., and P. Courtot, 1981. Evolution des hydrocarbures leum remained only in isolated soft sediment locations serving as dans l'eau et le sediments de l'Aber Benoit. in Amoco Cadiz: repositories for fine sediment from other parts of the Aber Benoit. Consequences d'une Pollution Accidentelle par les Hydrocar- These will reach a background state as microbial activity continues to bures; Fates and Effects of the Oil Spill. Centre National Pour degrade any petroleum fractions remaining. L'Exploitation des Oceans, Paris, ppl07-127 17. Oudot, J., P. Fusey, M. Van Praet, J. P. Feral, and F. Gaill, 1981. Hydrocarbon weathering in seashore invertebrates and sediments References over a two-year period following the Amoco Cadiz oil spill: influ- ence of microbial metabolism. Environmental Pollution Series A, 1. Allen, G., L. d'Ozouville, and J. l'Yavanc, 1978. Etat de la v26, pp93-110 pollution par les hydrocarbures dans l'Aber Benoit. in Amoco 18. Page, D. S., J. C. Foster, P. M. Fickett, and E. S. Gilfillan, 1988. Cadiz -Premieres Observations des Consequences a Court Terme Identification of petroleum sources in an area impacted by the de la Pollution par Hydrocarbures sur l'Environment Marin, G. Amoco Cadiz oil spill. Marine Pollution Bulletin, vl9, ppl07-115 Conan, L. d'Ozouville, and M. Marchand, eds. Centre National 19. Simonheit, B. R. T., 1978. The organic chemistry of marine sed- pour l'Exploitation des Oceans, Actes de Colloques, n6, pp97-114 iments. in Chemical Oceanography, J. P. Riley and R. Chester, 2. Atlas, R. M., P. D. Boehm, and J. A. Calder, 1981. Chemical eds., v7, pp233-311 and biological weathering of oil from the Amoco Cadiz oil spill- 20. Thompson, S. and G. Eglinton, 1978. Composition and sources age within the littoral zone. Estuarine and Coastal Marine Sci- of pollutant hydrocarbons in the Severn Estuary. Marine Pollu- ence, vl2, pp589-608 tion Bulletin, v9, ppl33-136 3. Berne, S. and L. d'Ozouville, 1979. Amoco Cadiz, Cartographie 21. Ward, D. M., R. M. Atlas, P. D. Boehm, and J. A. Calder, 1980. des Apports Pollutants et des Zones Contaminees. Centre Na- Microbial degradation and chemical evolution of oil from the tional pour l'Exploitation des Oceans, Brest, France. 175pp Amoco spill. Ambio, v9, pp277-283 Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1989/1/401/1741600/2169-3358-1989-1-401.pdf by guest on 27 September 2021