The Erika Oil Spill

C H A P T E R

18 The Erika Oil Spill: 10 Years Monitoring Program and Effects of the Weathering Processes Fanny Chever, Ronan Jezequel and Julien Guyomarch Centre de Documentation de Recherche d’Expe´rimentations, Brest, France

BIOGRAPHIES Dr. Fanny Chever joined Cedre (Centre of Documentation, Research and Experimentation on Accidental Water Pollution) in June 2015 after a PhD in Oceanography, applied to the speciation of iron in open ocean and its interaction with phytoplankton. At Cedre, she works as a chemist for the Analysis and Resources Department, within which she is in charge of studies on the weathering and dispersibility of oils. She is also involved as lecturer in training courses and she is a member of Cedre’s Emergency Response Team since 2016, as an appointed Duty Engineer. Dr. Ronan Je´ze´quel joined Cedre (Centre of Documentation, Research and Experimentation on Accidental Water Pollution) in 2000 as a PhD student. During his thesis, he studied the persistence of the Erika oil (1999) on the French Atlantic coastline. He works for the Research Department, within which he is in charge of studies on the medium and long-term behavior of oils. The different experiments (laboratory based and in situ) which he has overseen have enabled him to acquire a certain expertise in the chemistry of oil and in analysis techniques demonstrating natural oil weathering processes. Julien Guyomarch joined Cedre (Centre of Documentation, Research and Experimentation on Accidental Water Pollution) in 1997 and is in charge of studies on the short to medium-term behavior of crude or refined oils. The different experiments (laboratory based, pilot scale, and in situ) which he has overseen have enabled him to acquire a certain expertise in the chemistry of hydrocarbons and more specifically in analytical techniques characterizing oils and demonstrating oil weathering processes. This knowledge also includes the assessment of response techniques (chemical dispersion, mechanical recovery, bioremediation, etc.) according to the oil nature and its weathering stage. He is also in charge of the development of analytical techniques, mainly by gas chromatography coupled to mass spectrometry, and associated with microextraction techniques. He is also member of the Oil Spill Identification Network (OSINET) working group, and was involved in the field of oil identification in the marine environment at the occasion of several major (Erika, Prestige, et al.) or minor oil spills.

18.1 INTRODUCTION On 11 December 1999, the Maltese tanker Erika, laden with 31,000 tons of heavy fuel oil (HFO; fuel n
6), en route from Dunkirk (France) to Livorno (Italy) in very rough sea conditions (wind, force 8 to 9, with 6 m swell), was faced with structural problems off the Bay of Biscay. After sending an alert message, then proceeding to transfer cargo from tank to tank, the captain informed the French authorities that the situation was under control and that Oil Spill Environmental Forensics Case Studies. DOI: http://dx.doi.org/10.1016/B978-0-12-804434-6.00018-5

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18. THE ERIKA OIL SPILL: 10 YEARS MONITORING PROGRAM AND EFFECTS OF THE WEATHERING PROCESSES

he was heading to the port of Donges at reduced speed. At 6:05 a.m. the following day, he sent a Mayday: The ship was breaking in two. A rescue operation was immediately launched and the crew was winched to safety by French Navy helicopters, backed up by Royal Navy reinforcements, in extremely difficult conditions. The Erika split in two at 8:15 a.m. (local time) in international waters, about thirty miles south of Penmarc’h (Southern Brittany; Fig. 18.2). The quantity of oil spilt at that time was estimated between 7000 and 10,000 tons. The bow sank the following night, a small distance away from the place where the ship had broken up. The stern was taken in tow by a salvage tug on 12 December at 2:15 p.m., to avoid it drifting towards the French island of Belle-Ile, and it sank the following day at 2:50 p.m. The two parts of the wreck ended up 10 km apart from each other, in water 120 m deep. Initial aerial survey missions carried out by the French Customs and French Navy planes reported slicks drifting at sea, one of which was 15 km long and estimated at 3000 tons. The slicks were moving eastwards at a speed of about 1.2 knots. The first stranded oil on the shoreline was noticed in Southern Finistere 11 days after the accident, on 23 December. Scattered oil stranding continued the following days, contaminating some islands on 25 December, and the mainland shoreline on 27 December. Owing to rough weather conditions (wind over 100 km/h, blowing perpendicular to the coast) with springtides, the pollution was thrown up to high level of the shoreline, reaching the top of cliffs exceeding 10 m. On 26 December, 14 days after the sinking, the bulk of the pollution reached the shoreline which was partly covered with a viscous oil layer, 5 to 30 cm thick and several meters wide. Ultimately, around 400 km of shoreline were impacted by the Erika spill. At that time, no systematic analyses were performed on the samples collected on the shoreline in order to prove the origin of the contamination. However, from 2000, a follow-up study was initiated at Cedre with the objective of monitoring the fate and behavior of the oil, in terms of chemical composition and environmental impacts. Oil samples were regularly collected over a period of 10 years, some small areas of polluted sites being voluntarily not cleaned thereby allowing for this long-term sampling, leading to a significant set of data. In addition, some field studies were conducted using the Erika oil in order to better understand the modification of the oil composition according to its exposure to environmental conditions. Finally, laboratory and field samples were analyzed in the framework of a round-robin test organized within the OSINET group.

18.2 PHYSICALCHEMICAL PROPERTIES OF THE ERIKA OIL The Erika oil is an HFO (fuel n
6) characterized by a viscosity of 42,000 mPa.s (at 12
C) and a density of 1.002 (g/mL). Chemical fractions (saturates, aromatics, resins, and asphaltenes) were determined using an high pressure liquid chromatography (HPLC) technique (Jezequel, 2005). Table 18.1 presents the physicalchemical properties of the Erika oil. Aromatics can be subdivided in four groups depending on the number of rings contained in the compound: Monoaromatics (F1), diaromatics (F2), dibenzothiophenes/triaromatics (F3), and aromatics with four or more rings (F4). The contribution of those families to the total oil is 15%, 9%, 19%, and 12%, respectively for the F1, F2, F3, and F4 groups. Fig. 18.1 exhibits the gas chromatography-mass spectrometry (GC-MS) chromatograms in scan mode of saturates and aromatics of the Erika oil. n-Alkanes and resolved polyaromatic hydrocarbons (PAHs) (parents and alkylated), commonly used to evaluate the potential of degradation, represent a small fraction of the total oil, respectively 2.2% and 10.1%, the largest part of saturates and aromatics being constituted of unresolved complex mixture (UCM).

18.3 NATURAL DEGRADATION OF THE ERIKA OIL (10-YEAR MONITORING PROGRAM) Once spilled at sea, oils are subjected to natural weathering processes such as evaporation, dissolution, biodegradation, and photooxidation leading to changes in their chemical compositions. In order to identify the origin of oil patches washed ashore and the weathering processes that have affected it, evolution of abundance of the different chemical families are studied. From March 2001 to December 2004, a monitoring study was carried out in the frame of a French program supported by the French Ministry of Environment in order to assess the natural degradation of the persistent Erika oil on different substrates and exposed to different environmental conditions (Jezequel, 2005). Seventeen sites representative of the Atlantic shoreline and affected by the pollution were selected. At those sites, oil

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18.3 NATURAL DEGRADATION OF THE ERIKA OIL (10-YEAR MONITORING PROGRAM)

TABLE 18.1 PhysicalChemical Properties of the Erika Oil Erika

Properties


Viscosity (mPa.s, 12 C)

42,000

Density

1.002


3




Flash point ( C)

.100

Saturates (%)

23

Aromatics (%)

55

Resins (%)

14

Asphaltenes (%)

8

Pour point ( C)

FIGURE 18.1

Chromatograms (scan mode) of the Erika oil, (A) saturates, (B) aromatics.

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patches were voluntarily not recovered and were periodically sampled in order to monitor the fate and behavior of the oil with time. Fig. 18.2 shows the location of the selected sites. The selected sites differed by their exposition to hydrodynamic conditions (protected or exposed sites), the different types of substrates (sand, rocks, marsh), their exposition to the sun, and the littoral zones affected by the pollutant (littoral or supralittoral). The thickness of the oil layers present on the different substrates varied from ,1 mm to more than 4 mm. From this survey, a total of 189 samples were analyzed by GC-MS in Selected Ion Monitoring (SIM) mode for the quantification of n-alkanes (from n-C10 to n-C35 plus isoprenoids pristane and phytane), biomarkers (hopanes/steranes) and PAHs (from two to four rings, parents and alkylated up to four additional carbons). Fig. 18.3 represents the evolution with time of heavy aromatics (from phenanthrene to C3-chrysenes) and heavy alkanes (n-C25 to n-C35). All values were normalized to hopane, used as a conserved internal marker within the oil to follow the disappearance of other components (Prince et al., 1994) and to the original Erika oil. As such, all normalized values are reported in hopane units (HU). Data collected within the same year appear with the same symbol. Most of the data were located above the 1:1 line which highlights the more important degradation of the heavy alkanes compared to the heavy PAHs. For all the field studies, data were dispersed over the whole range of data. Those results show that different environmental conditions (exposition to solar radiation, littoral zones, thickness of the oil patch, etc.) lead to different weathering processes, and so to different chemical evolutions of the oil. However, when taking into account only the mean value of each field study on a yearly basis (represented in Fig. 18.3 by bigger dots on the inserted graph at the bottom right corner), a clear trend appeared highlighting the progressive loss of heavy compounds with time. At the end of the study in 2004, five sites were still monitored. Monitoring stopped at the other sites because of natural physical removal of the oil that led to the disappearance of the oil and/or because another major oil spill (Prestige in November 2002) along the Atlantic coastline had led to a new oil’s arrival. Among the five sites (A, B, C, D, and E, Fig. 18.4), site A was characterized by a thick oil layer (4 cm) and was located in a sheltered environment (between rocks) not exposed to solar radiations. The other sites were characterized by a thinner oil layer (12 cm) and are located on rock surfaces (B, C, and E) and a maritime marsh (D). Contrary to the site A

FIGURE 18.2 Atlantic coastline impacted by the Erika oil (represented by the black line) and location of the monitored sites (represented by the grey circles). Figures in brackets represent the number of sites sampled in each department.

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18.3 NATURAL DEGRADATION OF THE ERIKA OIL (10-YEAR MONITORING PROGRAM)

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FIGURE 18.3 Heavy aromatics (HU) versus heavy alkanes (HU), normalized to the initial values. HU, hopane units; as data were normalized to hopane.

FIGURE 18.4

Relative abundances (in HU) of each chemical family for the samples collected in 2004.

where the oil was still viscous, the oil of the four other sites looked like asphalt pavement. Environmental parameters characterizing the oil collected at the five sites are detailed in Table 18.2. Fig. 18.4 represents the repartition of the different chemical families of the five samples collected in December 2004, compared with the original Erika oil (T0). Samples were analyzed using scan mode in order to obtain the abundance (in HU) of the saturate 1 aromatic fractions (resolved peaks 1 UCM). The abundance of the different chemical fractions was then calculated in HU using equation 1 (X 5 saturates, aromatics, resins; Jezequel and Merlin, 2012). Asphaltenes content was determined by gravimetric analyses after precipitation in n-pentane. XðHUÞ 5 %X 

resolvedðHUÞ 1 UCMðHUÞ %saturates 1 %aromatics

Sample A clearly differed from the other samples. The main difference between the site A and the other ones was the exposition to solar radiation and so to photooxidation processes and the thickness of the oil layer. The mean degradation of the oil was 50% for samples exposed to solar radiations and 16% for the Site A. Except this last site, samples were characterized by a high abundance of polar compounds (resins and asphaltenes) that represented nearly 50% of the oil. This increase of polar compounds is due to metabolites generated during

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18. THE ERIKA OIL SPILL: 10 YEARS MONITORING PROGRAM AND EFFECTS OF THE WEATHERING PROCESSES

TABLE 18.2 Environmental Parameters and Depletion Percentage of the Heavy n-Alkanes and Heavy PAHs of the Five Sites Monitored in 2004 A

B

C

D

E

ENVIRONMENTAL PARAMETERS Solar radiation

2

1

1

1

1

Oil thickness (cm)

4

2

1

1

1

Littoral zone

Littoral

Supralittoral

Supralittoral

Littoral

Littoral

Heavy n-alkanes (%)

50

97

100

100

100

Heavy PAHs (%)

28

61

69

91

79

CHEMICAL EVOLUTION

FIGURE 18.5 Degradation of chrysene (C) and some of its alkylated derivatives (C1, C2, and C3 refer to methyl, dimethyl and ethyl, and trimethyl, methylethyl, and propyl-chrysenes, respectively) in oil samples from Groups I, II, and III. The number above the brackets represents the mean and standard deviation of percentage of degradation of total chrysenes (C 1 C1 1 C2 1 C3).

incomplete biodegradation of hydrocarbons (Haesler and Ballerini, 2002) and/or products of photooxidation (Garrett et al., 1998). This high amount of resins and asphaltenes explains the bituminous-like aspect of the oil collected at that time. From the Table 18.2 it appears that for the sample characterized by a thick oil layer and that was not affected by photooxidation process (Site A), 50% of the heavy n-alkanes remained present in the oil. Heavy PAHs were also degraded, between 61% and 91% were lost at sites B, C, D, and E, whereas only 28% were lost for site A. Sites located in littoral zones have lost from 79% (Site E) to 91% (Site D), against 61%69% for the sites located in supralittoral zones (Sites B and C). Hydrodynamic conditions seem to play a role in the degradation processes. This study dedicated to the assessment of the natural degradation of the Erika oil in natural environment highlights the importance of the physical form (thickness especially) of the oil on the intensity of some weathering processes (especially photooxidation). However, the complexity of the natural environment does not allow for the isolation and study of only one process in controlled conditions. It was also not possible to establish a relationship statistically validated between the degradation level and the type of exposure. Seven years after this monitoring study (from March 2001 to December 2004), a last sampling was performed in 2010 for a limited number of sites and environment conditions (Jezequel and Poncet, 2011). This study was focused on the exposure of the oil to solar radiation. A principal component analysis (The Unscrambler v9.7, CAMO software AS) was employed as a means of easily isolating different groups of samples according to the degradation rate of n-alkanes and PAHs. The principal component analysis (PCA) results clearly distinguish three groups of samples/data (data not shown) that correspond to exposure conditions: Group I for the highest level of exposure, Group II for a moderate exposure, and Group III for the sheltered samples. These results show that the differences in degradation rates of Erika oil were mainly due to the exposure level and consequently could probably be attributed to the photooxidation process. To confirm this, losses of chrysenes (parent and alkylated forms) were calculated for the previously defined groups and are presented in Fig. 18.5. Chrysenes, as with all heavy polycyclic compounds, are known to be

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18.4 STUDY IN CONTROLLED CONDITIONS

393

sensitive to photooxidation process and not easily biodegraded (Wang et al., 1994, Garrett et al., 1998, Hadibarata et al., 2009). Fig. 18.5 demonstrates that chrysenes degradation is significantly different between each group (63 6 4% in Group I, 28 6 8% in Group II, and 5 6 2% in Group III). Nevertheless, considering each group individually, the degradation rate are inversely proportional to the degree of alkylation which is typical of the biodegradation process (C . C1 . C2 . C3; Wang et al., 1994, Wang and Fingas, 1997, Michel and Hayes, 1999) suggesting during 10 years in environment, heaviest compounds are subject to biodegradation and photooxidation.

18.4 STUDY IN CONTROLLED CONDITIONS In order to improve the knowledge on the intensity of the natural degradation processes affecting the Erika oil, experiments under controlled conditions were carried out (Jezequel et al., 2003). Granite tiles coated with a thin layer of the Erika oil (200 μm) were fixed to the two faces of the pier of an islet located in the roadstead of Brest (Brittany, France) and were allowed to weather naturally for 216 days (Fig. 18.6). The northern face of the pier was exposed to natural agitation and did not receive direct solar radiation. The Southern face of the pier was directly exposed to solar radiation and was less exposed to natural agitation. Those tiles were installed to a height that allowed two cycles of immersion/emersion per day and were removed at different time steps for chemical analysis. Fig. 18.7 shows the evolution of the percentage of abundance of the three families: Saturates, aromatics, and polar (resins and asphaltenes), over the 216 days of the study. The main observation was the chemical changes were much more important for oil on the tiles located on the South face of the pier. Fig. 18.6 shows the loss of aromatic compounds associated with the increase of the polar fraction, especially for the tiles located on the South face of the pier. This is in accordance with the results observed during the monitoring study: Exposition to solar radiation is an important, and even sometimes, a prevailing parameter explaining the degradation of the oil. Fig. 18.8 details those results. Chromatograms of the saturates/aromatics compounds in scan modes are shown (with the abundance of the resolved peaks and UCM) as well as the distribution of abundances of the different chemical families, for three time steps (T0, T1 5 33 days, and Tf 5 216 days). From the chromatograms, it can be observed that the degradation rate of the UCM was more important for the samples located at the South face (67%) compared with the samples from the North face (44%) which is in accordance with the higher sensitivity of ramified compounds to photooxidation. Additionally, the total degradation of the oil was more pronounced on the South face (51%) compared with the North face (39%). At the end of the experiment, the degradation rate of the resolved compounds was of the same order for the two expositions: 76% for the samples located on the north face, 72% for the samples located on the South face. The lightest n-alkanes and PAHs were lost during the first month of the experiment, and in a general way, n-alkanes were more degraded on the North face. This last observation could be due to a warming of the substrate (tiles and oil layer) on the South face, inhibiting the bacterial growth. Comparing the percentage of the chemical families at the end of the experiment for the North and the South pier, it appeared that the oils significantly impacted by photooxidation processes were highly weathered compared to oils mainly impacted by biodegradation. For those photooxidized oils, a drastic loss of aromatics and an increase of polar fraction (which represents nearly half of the oil) were observed, which is characteristic of asphalt pavement.

FIGURE 18.6

Pictures of (A) the tiles coated with the Erika oil and (B) fixed to the pier.

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18. THE ERIKA OIL SPILL: 10 YEARS MONITORING PROGRAM AND EFFECTS OF THE WEATHERING PROCESSES

FIGURE 18.7 Ternary plot showing the evolution of the abundance (in %) of the three chemical families (saturates, aromatics, and polar) over 216 days (the original oil is represented by a star and its composition is transposed by dashed lines on the three axes).

FIGURE 18.8 Percentages of chemical families and chromatograms (scan mode) of the saturates/aromatics fractions for the tiles located on the North and the South faces of the pier. T0 5 0 days, T1 5 33 days, and Tf 5 216 days.

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18.5 STUDY OF MOLECULAR RATIOS

18.5 STUDY OF MOLECULAR RATIOS During the OSINET round-robin test 2011, the original Erika oil was compared with several naturally and artificially weathered Erika oils. Artificially weathered samples were processed at CEDRE laboratory: One sample was biodegraded at the laboratory and another one was exposed outside for three months (the oil being deposited on granite tiles), prone to photooxidation processes. Naturally weathered samples were collected 11 years after the accident on the Atlantic shoreline impacted by the spill at the time of the pollution. For the OSINET round-robin testing, the discussion focused on comparisons of the fresh oil and two weathered samples: The artificially weathered oil prone to photooxidation process and a naturally weathered oil collected in the upper part of the beach, in the middle of the vegetation. Samples were analyzed by gas chromatography / flame ionisation detection (GC/FID) and GC/MS according to conditions described in the CEN guidelines (CEN, 2012). Samples were first compared by using the GC/FID patterns to point out the most significant differences. The GC/MS analyses were then used, either to confirm the significant variations obtained from the GC/FID screening, or to enable conclusions of match or nonmatch in case of similarities of GC/FID patterns. The GC/FID chromatograms of the three samples are presented in Fig. 18.9. Chromatogram pattern of the source sample is typical from a HFO: Abundance of light aromatics compounds eluting between 10 and 15 minutes, which correspond to aromatic-rich distillate added to a residue, which is characterized with the abundance of the UCM and the alkanes with high boiling-point range. As regards the chromatograms, the naturally weathered sample appears to be highly degraded as most of the alkanes and aromatics compounds disappeared. Fig. 18.10 presents “percentage weathering” plots (PW-Plots) of the weathered samples based on GC/MS analyses. On these graphs, a range of PAHs and biomarkers (compound or compound group) are normalized to a nonweathered compound [here, the hopane (30ab)] and compared to the unweathered Erika oil. Results are sorted on retention time. A data points in the plot represent the concentration of a compound/compound group in the spill sample relative to the concentration of the same compound or compound group in the source sample (CEN, 2012). Response_ S

ig n a l:

R

J _ S

O

U

R

C E

0 0 0 0 0 0 . D

\

F I D

1 A

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h

1400000 1300000 1200000 1100000 1000000 900000 800000 700000 600000 500000 400000 300000 200000 100000 5.00

10.00

15.00

20.00

Ti me

25.00

30.00

35.00

40.00

45.00

Erika Oil Response_

Response_ S

ig

n

a

l:

R

J _

S

P

I L

L

2

. D

\

F I D

1

A

. c

h

S

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R

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P

I L L 3 . D

\

F I D

1 A

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h

1300000

1300000

1200000

1200000

1100000

1100000

1000000

1000000

900000

900000

800000 800000

700000 700000

600000

600000

500000

500000

400000

400000

300000

300000

200000

200000

100000

100000 5.00

10.00

15.00

20.00

25.00

30.00

40.00

0.00

45.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

Time

Time

Artificially weathered oil

FIGURE 18.9

35.00

Naturally weathered oil

GC/FID chromatograms of the fresh and weathered oil samples from OSINET 2001 round-robin testing.

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40.00

45.00

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18. THE ERIKA OIL SPILL: 10 YEARS MONITORING PROGRAM AND EFFECTS OF THE WEATHERING PROCESSES

FIGURE 18.10 PW-Plots of the weathered samples compared to the source sample (Erika oil) and normalized to hopane (30ab). TAS, triaromatic steranes, MPy, methylpyrenes, BFl, Benzofluorenes, MPhen, methylphenanthrene, DBT, dibenzothiophene.

On the two PW-Plots, the lighter compounds (characterized by a lower retention time) exhibited reduced abundance compared with heaviest ones. This is a common feature reflecting evaporation processes. The artificially weathered sample did not exhibit a reduction of n-C17/n-C18 alkanes compared to the isoprenoids pristane and phytane, minimizing biodegradation as weathering process. A reduction of the methylpyrenes (MPy, m/z 5 216; with the 1-methylpyrene being the most degraded) and the benzofluorenes [BFl; benzo(a) fluorene and benzo(b 1 c)fluorene], was also observed, demonstrating a photooxidation of the oil. Triaromatic steranes (TAS; m/z 5 231), biomarkers extremely stable against biodegradation, were also significantly reduced (  70% remaining). Photooxidation could thus also affect those aromatic biomarkers. Considering the naturally weathered sample, identification was difficult due to the high weathering stage. GC/MS results showed a severe degradation of most of the PAHs compounds and biomarkers. As already observed for the artificially weathered sample, MPy and BFl were degraded as well as methylphenanthrenes (MPhen) and bibenzothiophenes (DBT). This result confirms the importance of the photooxidation as weathering process. n-C17, n-C18, and the isoprenoids pristane and phytane were absent from this sample, which highlights the biodegradation process affecting the oil. Biodegradation was also confirmed by the degradation order of C1-fluoranthenes/pyrenes. As already observed in the artificially weathered sample, TAS were strongly degraded but not all the TAS were affected in the same way (SC26TA and RC26TA 1 SC27TA are more impacted than RC27TA and RC28TA). Steranes and diasteranes (m/z 5 217 and 218) that were not impacted in the sample photooxidized for three months were severely degraded in the naturally weathered sample. Steranes 27dbS and 27dbR were totally vanished from the oil (6%7% remaining) and diasteranes 27bbR 1 27bbS were highly degraded (22% remaining). Figs. 18.11 and 18.12 reflect this biomarkers degradation. Those figures present the ion chromatograms of steranes (m/z 217) and diasteranes (m/z 218) of the Erika oil compared with the naturally weathered oil. By comparing the two weathered samples, it appears that TAS can be degraded after only three months of exposure to solar radiation. An extended exposure (several years) leads to an additional degradation of these compounds, but with not all the TAS being affected in the same way. Steranes and diasteranes seem to be more resistant to photooxidation as they are not affected after three months weathering but on a long term, they seem to be extremely degraded as only B20% of the 27dbR, 27dbS, and 27bbR 1 27bbS remain (Figs. 18.11 and 18.12). In both figures, degradation of the 27dbS and 27dbR diasteranes and of the 27bbR 1 27bbS steranes clearly appears. Some hopanes compounds are also degraded after 10 years weathering (28ab and 30O). Kinetic studies on oils natural degradation highlighted compound ratios (diagnostic ratios, or Dr) used to evaluate the degree of weathering of oil. Those ratios involve compounds that exhibit different behaviors depending on the dominant process of degradation. Dr are ratios between the peak height (for individual peaks) or the peak area (for compound groups) of compounds selected by their diversity in chemical composition in petroleum and petroleum products and on their known behavior in weathering process (CEN, 2012). Any measured difference in a Dr between two samples greater than 14% relative difference is regarded as significant, meaning that these two ratios are statistically different (CEN, 2012). When looking at the relative differences of the 25 commonly studied Dr, most of them appear to be significantly higher than 14%, especially for the naturally weathered sample (Table 18.3). Several studies have already shown the degradation of biomarkers for heavily weathered oils (Munoz et al., 1997; Wang et al., 2000). Some Dr ratios are thus not robust enough to compare spill to source samples.

OIL SPILL ENVIRONMENTAL FORENSICS CASE STUDIES

FIGURE 18.11

Ion chromatograms of steranes (m/z 217) of the Erika oil and the naturally weathered Erika oil.

FIGURE 18.12

Ion chromatograms of steranes (m/z 218) of the Erika oil and the naturally weathered Erika oil.

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18. THE ERIKA OIL SPILL: 10 YEARS MONITORING PROGRAM AND EFFECTS OF THE WEATHERING PROCESSES

TABLE 18.3 Relative Differences Between the Dr (in %) Between the Weathered Samples and the Erika Oil for Common Dr in the CEN (2012) Guideline Relative difference (%)

Artificially weathered sample

Naturally weathered sample

NR-C17/pris

7

3

NR-C18/phy

14

6

NR-pris/phy

76

22

NR-4-MD/1-MD

27

120

NR-2-MP/1-MP

9

46

NR-2MF/4-Mpy

22

184

NR-B(a)F/4-Mpy

71

145

COMMON DR

NR-B(b 1 c)F/4-Mpy

119

183

NR-2Mpy/4-Mpy

9

112

NR-1Mpy/4-Mpy

50

89

NR-Retene/T-M-phen

39

16

NR-BNT/T-M-phen

59

117

NR-27Ts/30ab

5

6

NR-27Tm/30ab

2

17

NR-28ab/30ab

1

31

NR-29ab/30ab

2

3

NR-30O/30ab

26

25

NR-31abS/30ab

3

1

NR-30G/30ab

5

15

NR-27dbR/27dbS

6

15

NR-27bb/29bb

1

131

NR-SC26/RC26 1 SC27

15

28

NR-SC28/RC26 1 SC27

1

48

NR-RC27/RC26 1 SC27

2

21

NR-RC28/RC26 1 SC27

11

34

29aaS/29aaR

9

5

[(RC26TA 1 SC27TA) 1 SC28TA/RC28TA]

3

3

ADDITIONAL RATIOS

Additional ratios, taking into account stable compounds from the steranes and TAS families were analyzed in order to compare hardly weathered oils to sources. Those ratios, listed at the bottom of Table 18.3, were mainly used in geochemical investigations, as they were more stable over the long time of weathering.

18.6 CONCLUSION The Erika oil was an opportunity to study the fate and behavior of an HFO experiencing natural weathering processes. Samples were collected over a period of 11 years and were analyzed in order to study the evolution of chemical families (saturates, aromatics, resins, and asphaltenes) with time and from locations with different

OIL SPILL ENVIRONMENTAL FORENSICS CASE STUDIES

REFERENCES

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environmental conditions. Samples collected along the Atlantic shoreline between 2001 and 2004, demonstrate a general progressive loss of heavy alkanes and heavy aromatics with time. However, the high variability in environmental conditions characterizing the sites where the oil samples were collected during this study (e.g., variable exposure to solar radiation and tides) as well as the physical form of the oil (oil thickness) contributed to a variation in terms of alkanes and aromatics distribution. Study in a controlled environment allowed to better understand the effect of some weathering processes such as photooxidation on the chemical composition of the Erika oil. Oil exposed to solar radiation (and so to photooxidation processes) is prone to a drastic decrease of aromatics compounds along with an increase of the polar compounds (resins and asphaltenes). This observation explains the bituminous consistency/aspect of the oil after a few years in the environment. Saturates seem to be preserved but when looking at the n-alkanes, it appears that they are more degraded under conditions where no photooxidation occurs. Bacterial growth could be inhibited when exposure to solar radiation becomes too important. A round-robin test organized in the framework of the OSINET group allowed for the study of the evolution of compounds or group of compounds (PAHs and biomarkers) and the effects of artificial and natural weathering of Erika oils on the Dr commonly used to compare oils. This study highlighted the degradation of some stable biomarkers such as TAS. It also showed that the common Dr used to evaluate the potential “match” or “not match” between spills and sources via CEN (2012) are not robust enough in cases involving severely weathered oils. Additional ratios based on the specific composition of the oil, such as are used for geochemical investigations, can be used such cases. Thanks to this 10-year, long-term monitoring study following the Erika oil spill, the importance of photooxidation as weathering process has been highlighted. After more than 10 years of natural weathering, it appears that even very robust compounds such as biomarkers from the steranes, disteranes, TAS, and hopanes families can be extremely degraded or even entirely removed from the oil. In the case of HFOs (such as the Erika oil) containing an important fraction of aromatics (and especially heavy aromatics), the photooxidation process has a strong impact on the total degradation of the oil.

Acknowledgments The authors wish to express their sincere thanks to the OSINET (Oil Spill Identification Network) group.

References CEN Guideline, 2012. Oil spill identification  Waterbone petroleum and petroleum products. Part 2: Analytical methodology and interpretation of results based on GC-FID and GC-MS low resolution analyses. PD CEN/TR 15522-2:2012, British Standards Publication. Garrett, R.M., Pickering, I.J., Haith, C.E., Prince, R.C., 1998. Photooxidation of crude oils. Environ. Sci. Technol. 32, 37193723. Hadibarata, T., Tachibana, S., Itoh, K., 2009. Biodegradation of chrysene, an aromatic hydrocarbon by Polyporus sp. S133 in liquid medium. J. Hazard. Mater. 164, 911917. Haesler, F., Ballerini, D. 2002. De´gradation du fuel-oil n
6 de l’Erika dans l’environnement marin. Proceedings of the 3rd R&D Forum on High-density Oil Spill Response, Brest, France. pp. 129138. Jezequel, R., 2005. Pollution d’un littoral par fiouls lourds : Etude de l’influence des parame`tres environnementaux sur la persistance et l’e´volution chimique du polluant. The`se de doctorat de l’Universite´ de Bretagne Occidentale. Jezequel, R. Merlin, F.X., 2012. Influence of the nature and the weathering of oil on surfwashing efficiency: experimental study with the shoreline bench. Proceedings of the 2012 Artic and Marine Oilspill Program (AMOP) Technical Seminar, Environnement Canada, Vancouver. Jezequel, R., Poncet, F., 2011. The Erika oil spill, 10 years after: assessment of the natural weathering of the oil and natural recovery of vegetation. Proceedings of the 2011 International Oil Spill Conference. American Petroleum Institute, Washington, DC, March 2011, 2011, pp. abs165. Jezequel, R., Menot, L., Merlin, F.-X., Prince, R.C., 2003. Natural cleanup of heavy fuel oil on rock: an in-situ experiment. Mar. Pollut. Bull. 46, 983990. Michel, J., Hayes, M.O., 1999. Weathering patterns of oil residues eight years after the Exxon Valdez oil spill. Mar. Pollut. Bull. 38, 855863. Munoz, D., Guiliano, M., Doumenq, P., Jacquot, F., Scherrer, P., Mille, G., 1997. Long term evolution of petroleum biomarkers in mangrove soil (Guadeloupe). Mar. Pollut. Bull. 34, 868874. Prince, R.C., Elmendorf, D.L., Lute, J.R., Hsu, C.S., Haith, C.E., Senius, J.D., et al., 1994. 17α(H), 21β(H)-hopane as a conserved internal marker for estimating the biodegradation of crude oil. Environ. Sci. Technol. 28, 142145. Wang, Z., Fingas, M., 1997. Developments in the analysis of petroleum hydrocarbons in oils, petroleum products and oil-spill-related environmental samples by gas chromatography. J. Chromatogr. A. 774, 5178. Wang, Z., Fingas, M., Sergy, G., 1994. Study of 22-year-old Arrow spill sample using biomarker compounds by GC/MS. Environ. Sci. Technol. 28, 17331746. Wang, Z., Fingas, M., Owens, E.H., Sigouin, L., 2000. Study of Long-term Spilled Metula Oil: Degradation and Persistence of Petroleum Biomarkers. Proceedings of the 23th Artic and Marine Oilspill Program (AMOP) Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 99122.

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18. THE ERIKA OIL SPILL: 10 YEARS MONITORING PROGRAM AND EFFECTS OF THE WEATHERING PROCESSES

Further Reading Guyomarch, J., Budzinski, H., Chaumery, C., Haeseler, F., Mazeas, L., Merlin, F.-X., et al., 2001. The ERIKA oil spill: laboratory studies carried out to assist responders. Proceedings of the 2001 International Oil Spill Conference. American Petroleum Institute, Washington, DC, pp. 637647. Jezequel, R., Simon, R, Pirot, V., 2014. Assessment of oil burning efficiency: development of a Burning Bench. In proceedings of the 2014 International Oil Spill Conference, Savanah.

OIL SPILL ENVIRONMENTAL FORENSICS CASE STUDIES