Fingerprinting petroleum pollutants in the mediterranean sea

Fingerprinting petroleum pollutants in the mediterranean sea Fingerprinting petroleum pollutants in the mediterranean sea Fingerprinting petroleum pollutants in the mediterranean sea Fingerprinting petroleum pollutants in the mediterranean sea Fingerprinting petroleum pollutants in the mediterranean sea Fingerprinting petroleum pollutants in the mediterranean sea Fingerprinting petroleum pollutants in the mediterranean sea

Fingerprinting Petroleum Pollutants in the Mediterranean Sea J ALBAIGES Institute de Quimica Organica (CSIC), Jorge Girona Salgado, Barcelona-34, Spain ABSTRACT To confront the increasing and diversified petroleum pollution problems in the Mediterranean Sea there is a need to develop efficient analytical methods for the source identification of oil pollutants The paper describes an analytical approach for fingerprinting crude oils from different geographical areas, which are of particular incidence in the Mediterranean, and gives special attention to the identification of chronic pollution samples from the open sea The approach involves, in a first step, the determination of the S, Ni and V contents of the samples as well as the phytane/pristane ratio from the HRGC profiles (FID) With this information a general assignment of the type of the pollutants and the area from where they come can be established The precise identification of the samples source is attempted by a multi-fingerprinting procedure which is carried out by the use of selective detectors in GC Four profiles are considered, corresponding to total and polyaromatic hydrocarbons (FID), sulphur (FPD) and nitrogen (NPD) compounds Alternatively, the use of mass-fragmentography (GC-MSCOM) to obtain profiles for specific series of hydrocarbons of geochemical significance, such as C^n-C^Q acyclic isoprenoids, C97+ steranes and triterpanes is highly stressed KEY WORDS Isoprenoids Mass-fragmentography Mediterranean Sea Oil fingerprinting Petroleum pollution Selective GC deterctors Steranes Tar balls Triterpanes INTRODUCTION The Mediterranean Sea is among the first marine regions to show the symptoms of oil impact In fact, the observed concentrations of petroleum tars on its surface are one order of magnitude higher 69 70 J Albaiges than those generally found in any other regional seas (Nat Acad of Sei., 1975) The factors that contribute to this situation are several Thus, the particular hydrogeological conditions of the basin are such that oil entering or discharged there has little chance of leaving; it will stay and accumulate until it is degraded Moreover, the cyclonic drift of the water circulation tends to deposit the oil on the shores or to accumulate it at certain exposed points The oil handling activities brought about in the area, and specially the tanker traffic, are, in turn, quite important, as it is shown in Fig Finally, a lenient legislation has been unable to prevent intentional pollution Fig Location of the different sources of petroleum pollution in the Mediterranean Sea (courtesy of P Le Lourd, 1977) From all of the above, the oil pollution control in the Mediterranean has become a problem of mayor concern and consequently the development of analytical methods for the source identification of petroleum pollutants has received particular interest However, apart from the primary characterization of acute incidents , much attention has been recently devoted to the ultimate fate of spilled oils, specially for the assesment of their persistance into the sea and their contribution to the chronic pollution Chronic pollution by oil is, in the Mediterranean Sea, far more important than accidental pollution and it is generally assumed that is equally due to marine operational losses and to land-based discharges, including petroleum, petrochemicals and fossil fuel combustion products In these situations the chemical composition of the samples found in the sea can be considerably altered by environmental conditions Therefore, the ident:L Fingerprinting Petroleum Pollutants fication methods of oil pollutants should be able to deal with an entire spectrum of products of different origins and ages The present paper gives an account of the analytical approach used for fingerprinting oil products of different sources carried throughout the Mediterranean, with special reference to the identification of highly weathered samples This has been attempted by mass-fragmentographic fingerprinting of geochemically significant series of hydrocarbon components (biological markers) EXPERIMENTAL Reference samples of crude oils from Venezuela, Spain, Nigeria, Gabon, Libya, Algeria, Kuwait, Saudi Arabia, Iran, Irak, Oman and AbuDhabi were supplied by several refineries and production companies Tar ball samples were collected during a survey cruise (July 1977) between Cartagena (Spain) and Civittavechia (Italy), with a neuston net Samples were dissolved in toluene to eliminate extraneous materials and stored at -4QC until analysis Total sulphur content was determined by combustion (ASTM D-129; Bomb Method) and Ni and V by flamless atomic absorption spectrometry (Perkin Elmer 4000, equipped with a graphite HG-74 furnace) Dual FID/FPD and FID/NPD chromatograms were obtained by splitting the column effluent The former profiles were run on the deasphaltened oil residues in n-pentane (40 volumes) and the latter on the "polar oil fraction", which was isolated by partition of the deasphalted fraction into a cyclohexane-nitromethane mixture (1:5) The gas-Chromatograph (Perkin-Elmer 990) equipped with FI, FP and NP detectors was operated either with 9ft x 1/8" packed columns (1% Dexsil 300 or 3% OV-101 on Gas-Chrom Q 100-120) from 150 to 300QC at 6QC/min or with 200ft x 0.02" capillary columns (OV-101) from 120 to 280QC at 6QC/min., using He as carrier gas Mass-fragmentography (MF) was performed on a LKB 9000 S/PDP 11 E 10 computerized GC-MS system The injector and jet separator were maintained at 29 0QC and spectra were recorded and disk stored at sec intervals In this case, the "branched-cyclic fraction" was preferably used This was isolated throuhgout the previous recovery of the saturated fraction by conventional silica-gel adsorption chromatography, with an absorbent-sample ratio of 20 (eluting solvent: n-penatne), and subsequent inclusion in 30 fold excess of 5Â molecular sieves (solvent: iso-octane) RESULTS AND DISCUSSION All identification methods of oil pollutants are essentially a matching of samples based on the geochemical principle that no two oils have identical compositions unless they have identical histories Thus, in theory every oil product is unique; however, oil is a very complex mixture and anlysis is never complete, so 71 72 J Albaiges that very similar oils may appear to be identical Furthermore, exact correspondence of compositions of samples exposed to different environmental histories cannot be expected As there is no single analytical technique that can fully characterize an oil product, identification must be established by a series of analyses involving gecohemically characteristic and weathering-resistant sample parameters From the several techniques used for that purpose and according to our previous experience (Albaigés and others, 1976, 1979) we have selected the parameters indicated in Fig for building-up an inventory of possible source-oils in the Mediterranean, with which to compare the pollution samples All of these parameters have been suggested as the most suitable for a quick screening procedure of the pollutants (Brunnock and others, 1968; Zafiriou and others, 1973; Shekel and Ravid, 1977) A major advantage is that the information required is already available for most of the crude oils or is easily obtainable by routine analytical methods, and although the values reported in the literature are referred to unexposed oils, their correlation with pollution samples can be attempted, because the effects of weathering can be predicted (Brunnock and other,1968; Blumer and other, 1973) The HRGC pattern (FID) from which the phytane/pristane ratios are obtained permit, in addition, to assess the type of pollutant, namely, oil sludge, crude oil,technical fractions, etc As it can be seen in Fig 2, this characterization procedure allows a primary classification of the samples into several geographical groups In this manner, we have assigned to Middle East (M.E.) sources 86% of the pelagic tar ball samples collected during a survey cruise in the Western Mediterranean (Albaigés and others, 1979) However, this classification apparently leads to a certain overlaping and, in agreement with Jeffrey and others (1974), it is unlikely that with such parameters one could be able to ascertain the specific origin of the samples Their variation between crudes of the same area and their resistance to the sea weathering processes are not enough, in many cases, for providing the unequivocal identification of the pollutant Furthermore, this procedure cannot be applied to hydrocarbon samples found in highly dispersed forms, namely dissolved in water, adsorbed in sediments or biological samples, etc Thus, to provide furhter insights into these problems the composition of the samples should be better defined, and since the analysis of such chemically complicated samples is so extremely demanding, the great potential of GC can be particularly useful Fingerprinting Petroleum Pollutants ϊιηυ V/NI T.t-10.· Ph/Pt a « - v t Fig Chemical charaterization parameters of crude oils handled in the Western Mediterranean Numbers in brackets indicate the number of oils examined It is known that the GC traces of oil residues are characterized by a large unresolved envelope above the baseline, with small re solved peaks superposed Incidentally, the occurrence of this un resolved "hump" in sediment or biota samples has been generally considered as an indication of petroleum contamination, being however its origin unknown In order to get more information on the compounds included in this "hump" different types of detectors capable to enhance the response of specific series of compounds can be used Fig shows a set of profiles actually mea sureble on petroleum residues In addition to the already mentT oned hydrocarbon (HC) fingerprint (FID), profiles of sulphur and nitrogen containing compounds have been obtained with the ^use of FP and NP detectors, respectively In this manner, a multiprofile characterization procedure can be set up While the sulphur and HC profiles can be concurrently obtained straight from the samples by FPD and FID (Adlard and others, 1972), the smaller abundance of nitrogen compounds in unused oils requires their previous concentration For this reason, since the applied concentration procedure consisted in a simple liquidliquid extraction of the "polar oil fraction", polyaromatic hydro carbons (PAH) were also extracted together with the N-containing compounds This allowed the obtention of another representative FID profile (labeled FID(PAH) in Fig 3) which will^be useful in assigning the origin of the pollution in some chronic situations If the source of HC is predominantly petroleum, the chromatogram will contain a large number of peaks arising from alkylated PAH, whereas if the source is pyrolytic (air pollution) or coal tar 73 74 J Albaigés or creasote in nature, a more simple profile will be observed, corresponding to a higher predominance of the unsubstituted species over their alkylated homologs (LaFlamme and Hites, 1978) Fig GC profiles displayed by a Venezuelan crude oil residue (b.p 200Ω c ) Numbers over the peaks indicate the n-paraffin carbon atoms FID (HO/FPD profiles were obtained in a OV-101 capillary column, whilst the FID(PAH)/NPD in a 3% OV-101 packed column This fingerprinting procedure appeared quite succesful for the correlation of recent oil spillages with their suspected sources Nevertheless, there were some question about the general specificity of these profiles and their stability throughout the environmental exposure of the product at the sea Both aspects are of Fingerprinting Petroleum Pollutants interest in relation to pollution problems in the Mediterranean Sea, where, e.g., a particular incidence of very similar oil products from the M.E area and a wide occurrence of weathered pelagic tars resulting from tanker washings are expected Therefore a further evaluation of the method would seem in order The most significant Chromatographie profiles are those displayed by the FID(HC) and FPD Nevertheless Figs and show the exampie of oils of similar geological origin, exhibiti ng sufficiently similar patterns to render difficult the precise identification of the pollutant source The Aramco and Kuwait oi Is are apparently indistinguishable on the basis of the FID(HC) chromatogram and their FPD profiles exhibit only slight difference s, being the latter very similar to other M.E oils The NPD and FID(PAH) patterns are of more limited value for oil identification because of the smaller variability among products, apart from th e more time consuming procedure, as it has been recently noticed by Frame and others (1979) juUl ■wJ^^ "III _JL £> * * 11 IXUJUUWj WMMA 4»«& Fig 4.HR GC profiles (FID) of Kuwait and Aramco crude oils (x : pristane and phytane) In the case of the identification of oil spillages from tanker washings several additional difficulties arise In Fig it can be seen how the fingerprints of the original samples have been modified by the typical sludge peaks (n-C2c^.) a n d the lower fractions have been altered (affecting the phytane /pristane ratios) by the long exposure to sea weathering condi tions It is worth to mention here that the classification crit eria established in Fig 2, according to characteristic chemical parameters, 75 76 J Albaiges ROSTAND Fig HR GC profiles (FPD) of Middle East crude oils could also give unconclusive results on such samples, owing to their variable enrichment in paraffins during tanker transport or deposition at sea A final observation to be made on the applicability of this GC fingerprinting procedure is that the lack of knowledge about the nature of every resolved compound doesnft allow to elucidate the significance of qualitative variations among profiles , thus difficulting to ascertain when the slight differences absorved are attributable to different origins or weathering histories For these reasons we turned our attention to a more specific sample characterization procedure, which involves the fingerprinting of HC series of geochemical significance (biological markers) The occurrence and distribution of these series, which are included in the unresolved "hump" of the chromatogram, are related to the particular genetic history of the samples Fingerprinting Petroleum Pollutants Fig GC profiles of pelagic tar ball samples collected at the Western Mediterranean Weathering increases from S.N.16 to No.23 I I) I) 113 III) 191 Fig Petroleum biological markers I: acyclic isoprenoids Ilrsteranes Ill: rearranged steranes IV: hopanes Numbers indicate preferred fragmentation ions in the mass spectra 77 78 J Albaiges Among these series of HC we have the acyclic and polycyclic isoprenoid alkanes drawn in Fig 7, which seem to be resistant enough to sea weathering (Reed and Kaplan, 1977), thus being suitable for identification purposes Some recent reports (Rubinstein and others, 1977; Seifert and Moldowan, 1979) have specifically dealt with the biodégradation of these "markers1' and the results reported confirm that the profiles are severely modified only when conditions for total degradation of acyclic isoprenoids have prevailed; a rare ocurrence in the marine environment Taking into account that these compounds exhibit common ions in their mass spectra (see Fig ) , the M.F paterns from computerized GC-MS provide a powerful tool for the determination of distributions of homologous series, affording the relative abundances of individual members and epimeric and ring skeletal isomers Hence, crude oils quoted in Fig were characterized by the masschromatograms of m/e 183, 191, 217, 231 and 259 Although not all of them provide significant fingerprints for each one of the referred ions, in spite of this, relevant differences were still observed Fig shows a few examples from these crude oils The most abundant series is that of the triterpanes of the hopane type(IV,m/e 191) This family is formed by a series of C?7-C.r members The stereochemistry of the C-17 and C-21 in petroleum and matured HC samples is 17 e* (H), 21fi>(H) and 17 fi (H), 21 ex (H) with the 22R 4- 22S isomers, whilst in the precursor biological materials only the 17ß(H), 21*(H) with one diastereomer at position 22 is found This stereochemical fate has been considered as a definite test for oil pollution monitoring in sediments (Dastillung and Albrecht, 1976) In addition, two C^7 members are present, the 17cx (H) and 18c* (H)-trisnorhopanes, Their relative abundance being able to differentiate the previously reported Aramco and Kuwait crude oils The distribution of the individual members of this series was previously used, after isolation, by Pym and others (1975) to fingerprint M.E crude oils However, the advantages of the present MF procedure are obvious as far as the analysis time is concerned, as well as to the new identification possibilities offered by the multiparametric profiles hereing described Moreover, another identification parameter displayed by the m/e 191 MF is that corresponding to the C?n-Coc tricyclic diterpanes (Reed, 1977)which elute before the hopanes and appear with an asterisk in Fig In the sterane and methylsterane families two series of compounds can be expected: the normal (II, m/e 217, 31) and the rearranged steranes (III, m/e 259, 273), the latter occurring exclusively in petroleum and other geochemically matured samples Variations in the stereochemistry of carbons 5, 14, 20 and 24 afford a very complex pattern (Ensminger and others, 1978)and give complementary evidence of fossil fuel origin, because the chiral centers are built biosynthetically in only one stereochemical configuration However, steranes seem to disappear earlier with maturation, hence N.A crude oils exhibit the common characteristic of having very small concentrations of these HC (Fig 8) Fingerprinting Petroleum Pollutants Fig MF profiles of Middle East (M.E.) and North African (N.A.) crude oils Long chain acyclic isoprenoids (C25~"C4Q^ ^ ' m ^ e ^' although not as usiquitous as the preceding series can be of interest in the identification of specific sources of pollutants For example, they have been found to be representative of the crude oils produced off-shore in the mediterranean Spanish coast; oils that, on the other hand, are difficult to differentiate from some N.A., owing to the similarity of their characterization parameters (Fig .2) The ability of this fingerprinting procedure to identify the specific source of long-lived petroleum residues in the open ocean (pelagic tar balls and petroleum particulates) is clearly shown in Fig The samples range from moderately to highly weathered crude oil sludges, according to their GC profiles, which are similar to those shown in Fig The chemical and Chromatographie approaches for their source identification gave rather dissapointing results V/Ni ratios were comprised in the ranges given in Fig for the M.E and S.U crude oils; however, the S contents were lower than 1%, probably due to the higher paraffin content of the samples, characteristic of the oil sludges Finally, phytante pristane rations were affected by the loss of the lower boiling fractions, primarily by evaporation Evaporation is also resposible for the removal of the most representative part of the GC profiles which is situated in the range of C ^ C n n-paraffins (see Fig 3) Nevertheless, MF profiles, which 79 J Albaiges 80 Fig MF profiles of four pelagic tar balls collected at the Western Mediterranean are not modified by any of the referred compositional and weathering factors, afford enough information to permit the correlation of the samples with Iranian crude oils In conclusion, it can be pointed out that novel molecular fingerprinting techniques, involving specific geochemical markers, are expected to be more conclusive than gross compositional parameters for determining sources, of fossil fuel contamination HRGC-MS-computer systems are able to furnish the corresponding^profiles without complex sample treatments Multiparametric profiles can be obtained from one run and can be easily stored for further processing In this respect a general effort is needed in order to complete a fingerprint catalogue of worldwide produced oils ACKNOWLEDGMENTS We are gratefully indebted to the Osborne Company (Pto de^Santa Maria, Cadiz) for financial support under the Award in Environmental Protection We also thank P Albrecht and G Teller for facilities provided for the use of the GC-MS-computer system of the Institut de Chimie (Université de Strasbourg) Fingerprinting Petroleum Pollutants REFERENCES Adlard, E.R., C.F Creaser and P.H.D Mathews (1972) Identification of hydrocarbon pollutants on seas and beaches by gas chromatography Anal Chem , 4_4, 4-7 Albaigés, J., J Rivera, J Torradas and M.R Cuberes (1976) Evaluation des méthodes chimiques, spéctroscopiques et chromatographiques pour 1Tidentification des pollutants pétroliers en mer Rev Inst Franỗais Pộtrole, 31, 427-450 Albaigộs, J., Borbon and J.Ros (1979) Source identification of tar balls from the Western Mediterranean IV Journées Etud Pollut (Antalya), 103-109 C.I.E.S.M Blumer, M., M Ehrhardt and J.H Jones (1973) The environmental fate of stranded crude oil Deep-Sea Res., 20, 239-259 Brunnock, J.V., D.F Druckworth and G.G Stephens (1968) Analysis of beach pollutants J Inst Petrol., 310-325 Dastillung, M and P Albrecht (1976) Molecular test for oil pollution in surface sediments Mar Poll Bull , 7_> 13-15 Ensminger, A., G Joly and P Albrecht (1978) Rearranged steranes in sediments and crude oils Tetr Letters, 1575-1578 Frame, G.M., G.A Flanigan and D.C Carmody (19 79) Application of GC using nitrogen-selective detection to oil spill identification J Chromatogr., 168, 365-376 Jeffrey, L.M., W.E Pequegnat, E.A Kennedy, A Vos and B.M James (19 74) Pelagic tar in the Gulf of Mexico and Caribbean Sea.Marine Pollution Monitoring (Petroleum), 233-235 US Nat Bureau Stand S.P 40 Wash D.C LaFlame, R.E and R Hites (1978) The global distribution of PAH in recent sediments Geochim Cosmochim Acta, 42, 289-303 LeLourd, P (1977) Oil pollution in the Mediterranean Sea.Ambio, IB, 317-320 National Academy of Sciences (1975) Petroleum in the Marine Environment 107 pp Wash D.C Pym, J.G., J.E Ray, G.W Smith and E.V Whitehead (1975) Petroleum triterpane fingerprinting of crude oils Anal Chem., 47, 1617-1622 Reed, W.E (1977) Molecular compositions of weathered petroleum and comparison with its possible source Geochim Cosmochim Acta, 4_1, 237-247 Reed, W.E and I.R Kaplan (19 77) The chemistry of marine petroleum seeps J Geochem Expl., _7, 255-293 Rubinstein, I., O.P Strausz, C Spyckerelle, R.J.Crawford and D.W Westlake (1977) The origin of oilsand bitumens of Alberta: a chemical and microbiological simulation study Geochim Cosmochim Acta, 41, 1341-1353 Seifert, W.K and J.M Moldowan~Tl9 79) The effect of biodégradation on steranes and terpanes in crude oils Geochim Cosmochim Acta, 43, 111-126 Shekel, Y and R Ravid (1977) Source of tar pollution on Israeli Mediterranean coast Environ Sei Technol., 11,502-505 Zafiriou, O.C., J Myers, R Bourbonniere and F.J Freestone (1973) Oil spill-source correlation by GC: an experimental evaluation of system performance Proc Joint Conf on Prevention and Control of Oil Spills, 153-159 A.P.I Wash.D.C 81 ... exposure of the product at the sea Both aspects are of Fingerprinting Petroleum Pollutants interest in relation to pollution problems in the Mediterranean Sea, where, e.g., a particular incidence... owing to their variable enrichment in paraffins during tanker transport or deposition at sea A final observation to be made on the applicability of this GC fingerprinting procedure is that the. .. of the samples found in the sea can be considerably altered by environmental conditions Therefore, the ident:L Fingerprinting Petroleum Pollutants fication methods of oil pollutants should be