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  This article was downloaded by: [78.96.165.198]On: 22 October 2014, At: 12:59Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK Environmental Forensics Publication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/uenf20 Forensic Fingerprinting of Biomarkers for Oil SpillCharacterization and Source Identification Zhendi Wang a  , Scott A. Stout b  & Merv Fingas aa  Emergencies Science and Technology Division, Environmental Technology Centre,Environment Canada , Ottawa, Ontario, Canada b  NewFields , Rockland, MAPublished online: 23 Feb 2007. To cite this article:  Zhendi Wang , Scott A. Stout & Merv Fingas (2006) Forensic Fingerprinting of Biomarkers for Oil SpillCharacterization and Source Identification, Environmental Forensics, 7:2, 105-146, DOI: 10.1080/15275920600667104 To link to this article: http://dx.doi.org/10.1080/15275920600667104 PLEASE SCROLL DOWN FOR ARTICLETaylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of theContent. Any opinions and views expressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon andshould be independently verified with primary sources of information. Taylor and Francis shall not be liable forany losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoeveror howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions   Environmental Forensics , 7:105–146, 2006Copyright  C   Taylor & Francis Group, LLCISSN: 1527–5922 print / 1527–5930 onlineDOI: 10.1080/15275920600667104 Forensic Fingerprinting of Biomarkers for Oil SpillCharacterization and Source Identification Zhendi Wang, 1 Scott A. Stout, 2 and Merv Fingas 1 1  Emergencies Science and Technology Division, Environmental Technology Centre, Environment Canada,Ottawa, Ontario, Canada 2  NewFields, Rockland, MA Biomarkers are one of the most important hydrocarbon groups in petroleum. Biomarkers can be detected in low quantities (ppm and sub-ppm level) in the presence of a wide variety of other types of petroleum hydrocarbons by the use of the gas chromatography/massspectrometry (GC/MS). Relative to other hydrocarbon groups in oil such as alkanes and most aromatic compounds, biomarkersare more degradation-resistant in the environment. Furthermore, biomarkers formed under different geological conditions and agesmay exhibit different biomarker fingerprints. Therefore, chemical analysis of biomarkers generates information of great importanceto environmental forensic investigations in terms of determining the source of spilled oil, differentiating and correlating oils, and monitoringthedegradationprocessandweatheringstateofoilsunderawidevarietyofconditions.Thisarticlebrieflyreviewsbiomarker chemistry,biomarkercharacterizationandquantification,biomarkerdistributions,weatheringeffectsonbiomarkercomposition,bicyclic biomarkersesquiterpanesanddiamondoids,diagnosticratiosandcross-plotsofbiomarkers,uniquebiomarkers,applicationofbiomarker fingerprinting techniques for spill source identification, and application of multivariate statistical analysis for biomarker fingerprinting.Keywords: oil spill identification, biomarker fingerprinting, terpanes, steranes, sesquiterpanes, aromatic steranes Introduction Liquid petroleum (crude oil and the products refined from it) plays a pervasive role in modern society. As the population of the world increases and developing countries become more in-dustrialized,thedemandforenergygrowsworldwide(Figure1).Oil is currently the dominant energy source and it is expected toremain so over the next several decades. The worldwide extrac-tion,transportation,anduseofpetroleuminevitablyresultsinitsreleasetotheenvironment.Oilspillshavebecomeaglobalprob-lem. Based on analysis of data from a wide variety of sources,about 260,000 metric tons of petroleum each year on averagearereleasedtothewatersoffNorthAmerica.Annualworldwideestimates of petroleum input to the sea exceed 1,300,000 metrictons (NRC, 2002). In Canada, about 12 spills of more than 4000Larereportedeachday,ofwhichaboutonespillisintonavigablewaters. Most spills take place on land, including oil spills from pipelines, underground storage tanks, and aboveground storagecontainers. In the United States, about 25 such spills occur eachday into navigable waters and about 75 occur on land (Fingas,2001). Although large oil spills from tankers (such as the 1989  Exxon Valdez  , 1999  Erika , and 2002  Prestige  spills) occur in themarine environment, these spills only make up about 5% of oil Received 8 August 2005; accepted 25 January 2006.Address correspondence to Zhendi Wang, Emergencies Scienceand Technology Division, Environmental Technology Centre, Envi-ronment Canada, 335 River Rd., Ontario, K1A 0H3, Canada. E-mail:zhendi.wang@ec.gc.ca entering the sea. Most oil pollution in the oceans comes fromthe run-off of oil and fuel from land-based sources rather thanfrom accidental spills. Oil poses a range of environmental risksand causes wide public concerns when released into the envi-ronment, whether as catastrophic spills or chronic discharges.Therefore, to unambiguously characterize, identify, categorize,and quantify all sources of hydrocarbons entering the environ-ment is very important for environmental damage assessment,evaluation of the relative risks to the ecosystem posed by eachspill, and selecting appropriate spill response and taking effec-tive cleanup measures.Biomarkers play a very important role in characteriza-tion, correlation, differentiation, and source identification inenvironmental forensic investigations of oil spills. Biologicalmarkers or biomarkers are one of the most important hydro-carbon groups in petroleum for chemical fingerprinting. Theyare complex molecules derived from formerly living organisms.The biomarkers found in crude oils, rocks, and sediments arestable and show little or no changes in structures from their par-ent organic molecules, or so-called biogenic precursors (e.g.,terpenoids, sterols, and steroids), in living organisms, and thuscarryinformationaboutthenature,source,type,geologicalcon-ditions, and thermal history of these organisms. Biomarkershave for many years been widely used in petroleum explorationand reservoir geochemistry to obtain information valuable togeochemists such as the thermal maturity of the oil, the typeof source material, the depositional environment of the sourcerock, the approximate geological age of the source rock, and 105    D  o  w  n   l  o  a   d  e   d   b  y   [   7   8 .   9   6 .   1   6   5 .   1   9   8   ]  a   t   1   3  :   0   0   2   2   O  c   t  o   b  e  r   2   0   1   4  106 Z. Wang et al. Figure 1.  Worldwide demand and supply for liquid petroleum from 1970 to 2004 (data from the US Department of Energy – ref. DOE, 2004). the degree of biodegradation of the oil. An excellent book,  The Biomarker Guide: Interpreting Molecular Fossils in Petroleumand Ancient Sediments , on fundamentals of biomarker charac-terization, their application in geochemistry, and interpretationof biomarker data for oil exploration, was published in 1993(PetersandMoldowan,1993)andthesecondeditionofthebook recently has been fully updated and expanded (Peters et al.,2005). This new two-volume book provides a comprehensiveaccount of the role that biomarker technology plays both in petroleum exploration and in understanding earth history and  process.Biomarkers can be detected in low quantities (ppm and sub- ppm level) in the presence of a wide variety of other types of  petroleum hydrocarbons by the use of the gas chromatogra- phy/mass spectrometry (GC/MS). Relative to other hydrocar- bon groups such as alkanes and most aromatic compounds, biomarkers, in particular hopenoids and steroids (includingaromatic steroids), are more degradation-resistant in the envi-ronment. Furthermore, biomarkers formed under different ge-ological conditions and ages may exhibit different biomarker fingerprints. Therefore, chemical analysis of biomarkers gener-ates information of great importance to environmental forensicinvestigations in terms of determining the source of spilled oil,differentiatingandcorrelatingoils,andmonitoringthedegrada-tion process and weathering state of oils under a wide variety of conditions. Biomarkers have also proven useful in identificationofpetroleum-derivedcontaminantsinthemarineandaquaticen-vironments (Bence et al., 1996; Boehm et al., 1997; Hostettler et al., 1999a; Kvenvolden et al., 1995, 2002; Stout et al., 2002;Volkmanetal.,1997;Wangetal.,1994a,1994b,1999a;Zakariaet al., 2000) and in indicating chronic industrial and urban re-leases (Kaplan et al., 1997; Stout et al., 1998; Volkman et al.,1992a).This review focuses on discussion of biomarker chem-istry, overview of biomarker separation and analysis, biomarker distributions and weathering effects on biomarker distribu-tions, sesquiterpanes and diamondoids, diagnostic ratios and cross-plots of biomarkers, unique biomarkers, application of  biomarker fingerprinting techniques for spill oil source iden-tification, and application of multivariate statistical analysis for  biomarker fingerprinting and oil identification. Biomarker Chemistry Chemical Composition of Oil  Crude oils consist of complex mixtures of hydrocarbons and non-hydrocarbons that range from small, volatile compoundsto large, non-volatile ones. Hundreds to thousands of com- pounds have been identified in crude oils. Ultrahigh-resolutionFourier transform ion cyclotron resonance mass spectrometry(Marshall and Podgers, 2004) has recently revealed that crudeoil contains heteroatom-containing (N, O, S) organic compo-nents having more than 20,000 distinct elemental compositions(C c H h  N n O o S s ).Ingeneral,petroleumcomponentsareclassified in bulk groups of saturates, olefins, aromatics, resin (wide vari-ety of compounds containing sulfur, oxygen, and nitrogen), and asphaltenes (also called   SARA analysis ). Saturates  are a group of hydrocarbons composed of onlycarbon and hydrogen with no carbon–carbon double bonds.    D  o  w  n   l  o  a   d  e   d   b  y   [   7   8 .   9   6 .   1   6   5 .   1   9   8   ]  a   t   1   3  :   0   0   2   2   O  c   t  o   b  e  r   2   0   1   4  Forensic Fingerprinting of Biomarkers 107 Saturates are the predominant class of hydrocarbons in mostcrude oil. Saturates include straight chain and branched chain (also called   paraffins ) and cycloalkanes (also called  naphthenes ). Biomarker terpanes and steranes are branched cycloalkanes consisting of multiple condensed five- or six-carbonrings.Sesquiterpanesanddiamondoidsaresmallercyclic biomarkers, which can be particularly valuable for source iden-tification of lighter petroleum products.  Alkenes , commonlyreferred to as  olefins , are partially unsaturated hydrocarbonscharacterized by one or multiple double carbon–carbon bonds.These compounds are rare in crude oil but may be present insome petroleum products, having been formed during the re-fining process.  Aromatic hydrocarbons  are cyclic, planar com- pounds that resemble benzene in electronic configuration and chemical behavior. Aromatics in petroleum include the mono-aromatic hydrocarbons such as benzene, toluene, and ethylben-zene, and   o ,  m , and   p -xylene isomers (BTEX) and other alkyl-substituted benzene compounds (C n -benzenes), and polycyclicaromatichydrocarbons(PAHs)(whichincludeoil-characteristicalkylated C 0 - to C 4 -naphthalene, phenanthrene, dibenzothio- phene, fluorene, and chrysene homologous series and other United States Environmental Protection Agency (US EPA) pri-ority PAHs).  Polar compounds  are those with distinct regionsof positive and negative charge, as a result of bonding withatoms such as nitrogen, oxygen, or sulfur. Heavy oils generallycontain greater proportions of higher-boiling, more aromatic,and heteroatom-containing (N-, O-, S-, and metal-containing)constituents. In the petroleum industry, the smaller polar com- pounds are called   resins .  Asphaltenes  are a class of very largeheteroatom-containing compounds (Berkowitz, 1997; Speight,1999). They are not dissolved in petroleum but are dispersed ascolloids. Asphaltenes are generally defined, based on the solu-tion properties of petroleum residues in various solvents, as theoil constituents precipitated from oils and bitumen by natural processes or in laboratory by addition of excess  n -pentane or  n -hexane. Table 1 summarizes the typical bulk composition of some oils and petroleum products. Table 1.  Typical bulk composition of crude oils and petroleum products Compound Light HeavyGroup class Gasoline Diesel crude crude IFO Bunker C Saturates  50–60 65–95 55–90 25–80 25–45 20–40alkanes 45–55 35–45¸cyclo-alkanes  ∼ 5 30–50waxes 0–1 0–20 0–10 2–10 5–15 Olefins  5–10 0–10 – – – –  Aromatics  25–40 5–25 10–35 15–40 40–60 30–50BTEX 15–35 0 . 5–2 0 . 1–2 . 5 0 . 01–2 0 . 05–1 0–1PAHs 0 . 5–5 0 . 5–3 1–4 1–10 1–10 Polar compounds  – 0–2 1–15 5–40 15–25 10–30resins – 0–2 0–10 2–25 10–15 10–20asphaltenes – – 0–10 0–20 5–10 5–20 Sulphur  <0.05 0 . 05–0 . 5 0–2 0–5 0 . 5–2 2–4 Metals (ppm)  30–50 100–500 100–1000 100–2000 BTEX =  benzene, toluene, ethylbenzene, and xylenes; PAHs =  polycyclic aromatic hydrocarbons. The “Isoprene Rule” and Biomarker Families In 1887, German chemist Otto Wallach determined the struc-tures of several terpenes and discovered that all of them arecomposed of two or more five-carbon units of isoprene [2-methyl-1,3-butadiene, CH 2  = C(CH 3 ) − CH = CH 2 ]. The iso- prene unit maintains its isopentyl structure in a terpene, usuallywith modification of the isoprene double bonds. Compoundscomposed of isoprene subunits are called   terpenoids  or   iso- prenoids . Terpenoids can be classified according to the number of isoprene units from which they are biogenetically derived,even though some carbons may have been added or lost (Con-nolly and Hill, 1991). As for the oil saturated terpenoids, theyare generally categorized into families based on the approxi-mate number of isoprene subunits they contain. The various oilterpane families are composed of a wide variety of acyclic and cyclic structures (Peters et al., 2005):Hemiterpane (C 5 ): containing one isoprene subunit;Monoterpanes (C 10 ): containing two isoprene subunits;Sesquiterpanes (C 15 ): containing three isoprene subunits;Diterpanes (C 20 ): containing four isoprene subunits;Sesterterpanes (C 25 ): containing five isoprene subunits;Triterpanes & containing six isoprene subunits;steranes (C 30 ):Tetraterpanes (C 40 ): containing eight isoprene subunits;Polyterpanes (C 5n (n > 8) ): containing nine or more isoprenesubunits.As an example, Figures 2 and 3 show molecular structures of some representative acyclic and cyclic terpenoid compoundsin oil, respectively. The most common cyclic terpenoids inoil are terpanes, steranes and aromatic steranes. As a sum-mary, Table 2 lists important biomarker terpane, sterane, and aromatic sterane compounds, used frequently for oil spillidentification.    D  o  w  n   l  o  a   d  e   d   b  y   [   7   8 .   9   6 .   1   6   5 .   1   9   8   ]  a   t   1   3  :   0   0   2   2   O  c   t  o   b  e  r   2   0   1   4
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