- Email: [email protected]
“Unresolved Complex Mixture” (UCM): A brief history of the term and moving beyond it
Marine Pollution Bulletin 96 (2015) 29–31
Contents lists available at ScienceDirect
Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul
Viewpoint
‘‘Unresolved Complex Mixture’’ (UCM): A brief history of the term and moving beyond it John W. Farrington a,⇑, James G. Quinn b a b
MS#8, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA Graduate School of Oceanography, University of Rhode Island, 215 South Ferry Road, Narragansett, RI 02882-1197, USA
a r t i c l e
i n f o
Article history: Received 6 March 2015 Revised 17 April 2015 Accepted 18 April 2015 Available online 29 April 2015 Keywords: Unresolved Complex Mixture UCM Oil pollution
a b s t r a c t The term ‘‘Unresolved Complex Mixture’’ (UCM) has been used extensively for decades to describe a gas chromatographic characteristic indicative of the presence of fossil fuel hydrocarbons (mainly petroleum hydrocarbons) in hydrocarbons isolated from aquatic samples. We chronicle the origin of the term. While it is still a useful characteristic for screening samples, more modern higher resolution two dimensional gas chromatography and gas chromatography coupled with advanced mass spectrometry techniques (Time-of-Flight or Fourier Transform-Ion Cyclotron Resonance) should be employed for analyses of petroleum contaminated samples. This will facilitate advances in understanding of the origins, fates and effects of petroleum compounds in aquatic environments. Ó 2015 Elsevier Ltd. All rights reserved.
Advances in application of parallel chromatographic methods and three different types of mass spectrometry (MS) (e.g. Gough and Rowland, 1990) and multidimensional gas chromatography (GC) (e.g. Frysinger et al., 2003) or two-dimensional GC coupled with time of flight MS (e.g. Booth et al., 2007) have at least partially resolved or essentially completely resolved the Unresolved Complex Mixture of hydrocarbons in petroleum samples and in several environmental samples from petroleum contaminated or oil spill contaminated and polluted environments. The extent of the partial or essentially complete resolution depends on molecular weight range and molecular type of compounds present, e.g. No. 2 fuel oils are essentially completely resolved, and some crude oils are partially resolved. These advances have stimulated another round of inquiries similar to those we have been asked numerous times during the past forty years about the origin of the term ‘‘Unresolved Complex Mixture’’ or UCM, a term still in use as one indicator of petroleum or fossil fuel pollution (e.g. Wang et al., 2015). To our knowledge and extensive literature research, the term, including the shorthand notation UCM, was first used in our paper Farrington and Quinn (1973a). At that time, we had no inkling of how extensively it would be used. We provide here a short account of the history of the term which has been used in hundreds, if not thousands, of scientific papers, chapters and technical reports since 1973, including numerous papers published in Marine Pollution Bulletin. ⇑ Corresponding author. Tel.: +1 508 274 1926. E-mail addresses: [email protected] (J.W. Farrington), [email protected] (J.G. Quinn). http://dx.doi.org/10.1016/j.marpolbul.2015.04.039 0025-326X/Ó 2015 Elsevier Ltd. All rights reserved.
One of us (JWF) was a Ph.D. student advised by the other (JGQ) at the Graduate School of Oceanography, University of Rhode Island 1968–1971. JWF’s Ph. D. Dissertation research initially focused in part on the use of lipid class compounds in sewage discharges to Narragansett Bay, R.I. USA as a potential means of tracking sewage inputs to the bay. One of the target classes of compounds selected for testing was the class n-alkanes. We knew from earlier research that n-alkanes with an odd over even carbon number predominance in the molecular weight range of 23–31 carbons chain length were predominant in land plants as constituents of the waxy coating on plants (Eglinton et al., 1962a,b). Marine organisms did not have such an n-alkane distribution, with odd over even carbon number predominance in a limited range of 22–31 carbon chain length. (Clark and Blumer 1967, among others). We set out sampling sewage discharge waters from a large municipal sewage treatment plant, surface sediments in Narragansett Bay and hard shell clams (Mercenaria mercenaria), extracting the lipid class compounds, and isolating several classes of lipids by column chromatography (CC), thin layer chromatography (TLC), and analyzing the hydrocarbon fraction by gas chromatography using a packed column in a temperature programmed gas chromatograph (GC) equipped with a flame ionization detector connected to a strip chart recorder. These were our first hydrocarbon analyses and we expected to see a series of resolved n-alkanes, pristane and phytane peaks as had been reported in the literature for sediments and marine organisms and which we had replicated with standard mixtures of n-alkanes. Instead we had a slowly rising slightly wiggling graph trace over time, with a few small peaks on top of this line that
30
J.W. Farrington, J.G. Quinn / Marine Pollution Bulletin 96 (2015) 29–31
gradually came back to the column bleed background of the GC column as the temperature program run ended (Fig. 1). We thought that JWF had done something wrong. Several extractions, isolations by CC, TLC, and GC analyses were repeated. Nothing changed and we were perplexed. The gas chromatograms were placed on a shelf, the TLC isolates were stored in vials in a refrigerator, and JWF got on with the fatty acid analyses which were also part of his dissertation research. A few months later a clue to what we were measuring in the gas chromatograms of the hydrocarbons was discovered in an ongoing literature search. JGQ required all his students to participate in a coordinated lab group literature search on topics of interest to our group, e.g. lipids, hydrocarbons, fatty acids, triacylglycerols. As part of this, JWF was searching Chemical Abstracts when he came across an abstract of a paper ‘‘Microbiological Alterations of Crude oil in the Reservoir’’ by J.C. Winters and J.A. Williams presented at a Symposium on Petroleum Transformations in Geological Environments of the Division of Petroleum Chemistry, Inc. of the American Chemical Society Meeting, September 7–12, 1969. The abstract in Chemical Abstracts was intriguing. That division of the ACS had published extended abstracts from the ACS meetings and we requested one from the authors by mailing a reprint request card, a common practice in those days. The extended abstract arrived within a few weeks. It contained figures with reproductions of the packed column gas chromatograms of the unaltered reservoir crude oil of the Bell Creek Formation on the border of Montana and Wyoming, and gas chromatograms of a transect of samples from the near surface reservoir of that formation which received a groundwater incursion with nutrients and oxygen. The former contained many resolved peaks of n-alkanes and branched alkanes superimposed on a broad rising and falling background signal. For the latter, the n-alkane peaks were much reduced or missing for the transect samples and isoprenoid alkanes were predominant and superimposed on the rising and falling broad background signal. The broad, non-descript rising and then and falling gas chromatogram signal was attributed by inference
to a naphthenic (mainly cycloalkanes) character to the biodegraded crude oil (Winters and Williams, 1969) It was an ‘‘aha’’ moment for us. Immediately we reasoned that our gas chromatograms of alkane hydrocarbons isolated from sewage effluents, surface sediments and hard shell clams were of biodegraded oil and/or lubricating oil (known to be mainly naphthenic in composition) being discharged via the sewage effluent (and perhaps other sources) to Upper Narragansett Bay. In hindsight, one could argue we should have expected chronic oil released via sewage effluents. However, our literature search in 1968 and 1969 had yielded many papers about measurements of total ‘‘grease and oil’’ – meaning animal fats and vegetable oils mainly from household and restaurant sources, and some specific analyses of fatty acids. Shortly thereafter, in 1970 a paper was published reporting the presence of No. 2 fuel oil components in edible shellfish as result of the Barge Florida No. 2 Fuel Oil spill on September 16, 1969 at the coast of West Falmouth in Buzzards Bay, Massachusetts, USA (Blumer et al., 1970). The gas chromatograms again contained the series of resolved or partially resolved peaks on top of the broad rising and falling detector signal. In that publication, Blumer et al. designated the phenomenon as the unresolved background. Blumer et al. (1970, 1973) and Blumer and Sass (1972) designated this signal the unresolved envelope of oil compounds. The term unresolved envelope seemed like a good term to us and JWF used it in his Ph. D. dissertation to describe attributes of our hydrocarbon gas chromatograms from several samples of sewage effluents, surface sediment samples, and hard shell clams obtained in Narragansett Bay. JWF took a position as a Postdoctoral Investigator in Max Blumer’s laboratory at Woods Hole Oceanographic Institution in July 1971. Throughout the remainder of 1971 and into 1972 JWF presented seminars and talks at various places and meetings during which he presented slides with the term ‘‘unresolved envelope’’ while preparing papers from his dissertation for publication. One paper (Farrington and Quinn, 1973b) was prepared, submitted,
Fig. 1. Packed column gas chromatograms of hydrocarbons isolated from Narragansett Bay surface sediments (left column) and Mercenaria mercenaria (right column). N–C22– alkane added as internal standard in the right column chromatograms. Stations F.P. and E. were in the Providence River area of Upper Narragansett Bay that received municipal and storm sewer discharges from municipal Providence R.I., Stations D and C were in the mid to upper reaches of Narragansett Bay. Charlestown Pond is a rural area and the control for the study. The chromatogram trace for the Charlestown Pond sample is the same as for the laboratory control and indicates the GC baseline for the temperature controlled GC analysis. (Figure reproduced with permission from Farrington and Quinn (1973a)).
J.W. Farrington, J.G. Quinn / Marine Pollution Bulletin 96 (2015) 29–31
and accepted for publication in which we used the term unresolved envelope as used by Blumer et al. (1970, 1973) and Blumer and Sass (1972). During JWF’ seminars and talks, the term ‘‘unresolved envelope’’ was criticized by some analytical chemists as not worthy of mention because we ‘‘had failed to resolve the compounds yielding the signal’’. We understood that concern, but thought that the signal should not be ignored and we believed we were in good company in that regard. Other critics did not like the term ‘‘envelope’’. Some remarked during a few seminars that an ‘‘envelope was something in which one mailed a letter’’. These criticisms led JWF to suggest that we use the term ‘‘Unresolved Complex Mixture’’, which would acknowledge we had not resolved the components of this complex mixture, and use the words ‘‘complex mixture’’ as noting the presence of the complexity of hydrocarbons found in fossil fuels such as crude oil and fuels and coal extracts. In reproductions of the gas chromatograms we used the short hand UCM to label the Unresolved Complex Mixture when it was present (Farrington and Quinn, 1973a). Fig. 1. Our only caveat that this might not be petroleum hydrocarbons was a concern that perhaps hydrocarbons biosynthesized by a very complex assemblage of microbes in sewage might yield the UCM signal. Discussion with Oliver C. Zafiriou, also in Max Blumer’s laboratory at that time, about that possibility led to additional analyses of hydrocarbons from a large several kg sediment sample from Upper Narragansett Bay/Providence River and a companion paper to our 1973a paper (Zafiriou, 1973). He reported radiocarbon (D14C) activity for hydrocarbons extracted and isolated from the sample of sediment indicating that the carbon in hydrocarbons of the UCM were 80–97% fossil, consistent with a fossil fuel source. This type of measurement for the radiocarbon (D14C) activity of hydrocarbons extracted from surface sediments was repeated a few years later for a sediment sample from the New York Bight Sewage Sludge Dump site (Farrington and Tripp, 1977) and more recently for samples of coastal sediments, road dust and urban atmospheric particulate samples with the result that 90% or greater of the carbon of the UCM was fossil carbon and therefore arguably from fossil fuel contamination/pollution (White et al., 2013). Professor Kurt Grob, a pioneer in analytical chemistry especially using glass capillary gas chromatography, took up a challenge from Dr. Max Blumer during the period 1973–74 and proceeded to almost completely resolve all the hydrocarbon components in a diesel oil (similar in molecular weight range to No. 2 Fuel Oil) into individual GC peaks using ingenious but time consuming glass capillary chromatography with 70 m columns, 3 h temperature programmed techniques, and transfer of several minute time portions of the first capillary GC column to a second glass capillary column for further separation (Grob, 1975). His methods were the forerunners of modern two dimensional GC analyses. Unfortunately, the time consuming nature of the methodology, about three or usually more hours per GC analysis, and the difficult art of preparing the fragile glass capillary columns, precluded routine analyses of oil contaminated samples by this methodology for several years. Identification and quantitative analyses of the major polycyclic aromatic hydrocarbons (PAH) from fossil fuels and pyrogenic sources in the aromatic hydrocarbon fraction of extracts of environmental samples proceeded in the interim years via probe distillation MS and GS–MS (e.g. Youngblood and Blumer, 1975; Hites and Biemann, 1975). Despite these advances, there are many aromatic hydrocarbons in the aromatic fraction UCM which were not identified and quantified. A very important study by Booth et al. (2007) found that several of the compounds contributing to the aromatic hydrocarbon UCM are toxic. Booth et al. noted that the potential for adverse effects from the UCM aromatic compounds had been overlooked.
31
The UCM signal may continue to be a screening tool for identifying samples containing complex mixtures of hydrocarbons in samples to become candidates for further analyses. However, when complex mixtures are identified, we call for the routine application of more modern analytical techniques such as multidimensional GC capable of resolving the components of the UCM, coupled with various types of mass spectrometry to identify these components and quantify concentrations (e.g. Gros et al., 2014). Simultaneously, it is important to gain a better understanding of the relationship between the identified compounds and mixtures of compounds, bioaccumulation potential and biological effects as pointed out by Booth et al. (2007). Acknowledgements John W. Farrington conceived of the idea of this Viewpoint article and led the writing. James G. Quinn added substantive comments and suggestions. Both authors approve submission of the manuscript. The authors have no substantive conflicts of interest that pertain to this article to disclose. This manuscript was selffunded. Both authors are formally retired. References Blumer, M., Souza, G., Sass, J., 1970. Hydrocarbon pollution of edible shellfish by an oil spill. Mar. Biol. 5, 195–202. Blumer, M., Sass, J., 1972. Indigenous and petroleum-derived hydrocarbons in a polluted sediment. Mar. Pollut. Bull. 396, 92–94. Blumer, M., Ehrhardt, M., Jones, J.H., 1973. The environmental fate of stranded crude oil. Deep Sea Res. 20, 239–259. Booth, A.M., Sutton, P.A., Lewis, A.C., Scarlett, A., Chau, W., Widdows, J., Rowland, S.J., 2007. Unresolved complex mixtures of aromatic hydrocarbons: thousands of overlooked persistent, bioaccumulative, and toxic contaminants in mussels. Environ. Sci. Technol. 41, 457–464. Clark, R.C., Blumer, M., 1967. Distribution of n-paraffins in marine organisms and sediment. Limnol. Oceanog. 12 (1), 79–87. Eglinton, G., Hamilton, R.J., Raphael, R.A., 1962a. Hydrocarbon constituents of the wax coatings of plant leaves: a taxonomic survey. Nature 193, 739–742. Eglinton, G., Gonzalez, A.G., Hamilton, R.J., Raphael, R.A., 1962b. Hydrocarbon constituents of the wax coatings of plant leaves: a taxonomic survey. Phytochemistry 1, 89–102. Farrington, J.W., Quinn, J.G., 1973a. Petroleum hydrocarbons in Narragansett Bay I: survey of hydrocarbons in sediments and clams (Mercenaria mercenaria). Est. Coast. Mar. Sci. 1, 71–79. Farrington, J.W., Quinn, J.G., 1973b. Petroleum hydrocarbons and fatty acids in wastewater effluents. J. Water Pollut. Control Fed. 45 (4), 704–712. Farrington, J.W., Tripp, B.W., 1977. Hydrocarbons in Western North Atlantic surface sediments. Geochim. Cosmochim. Acta 41, 1627–1641. Frysinger, G.S., Gaines, R.B., Xu, L., Reddy, C.M., 2003. Resolving the unresolved complex mixture in petroleum contaminated sediments. Environ. Sci. Technol. 37, 1653–1662. Grob, K., 1975. The glass capillary column in gas chromatography. A tool and a technique. Chromatographia 8 (9), 423–433. Gros, J., Reddy, C.M., Aeppli, C., Nelson, R.K., Carmichael, C.A., Arey, J.S., 2014. Resolving biodegradation patterns of persistent saturated hydrocarbons in weathered oil samples from the Deepwater Horizon disaster. Environ. Sci. Technol. 48 (3), 1628–1637. Gough, M.A., Rowland, S.J., 1990. Characterization of unresolved complex mixtures of hydrocarbons in petroleum. Nature 344, 648–650. Hites, R.A., Biemann, W.G., 1975. Identification of specific organic compounds in a highly anoxic sediment by gas chromatographic mass spectrometry and high resolution mass spectrometry. Adv. Chem. Series Issue 147, 188–201. Wang, M., Wang, C., Hu, X., Zhang, H., He, S., Lv, S., 2015. Distributions and sources of petroleum, aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) in surface sediments from Bohai Bay and its adjacent river, China. Mar. Pollut. Bull. 90, 88–94. White, H.K., Xu, L., Hartmann, P., Quinn, J.G., Reddy, C.M., 2013. Unresolved Complex Mixture (UCM) in coastal environments is derived from fossil sources. Environ. Sci. Technol. 47, 726–731. Winters, J.C., Williams, J.A., 1969. Microbiological alteration of crude oil in the reservoir. Extended Abstract Symposium on Petroleum Transformations in Geological Environments, The Division of Petroleum Chemistry, Inc. American Chemical Society. E22-31. Youngblood, W., Blumer, M., 1975. Polycyclic aromatic hydrocarbons in the environment: homologous series in soils and recent marine sediments. Geochim. Cosmochim. Acta 39, 1303–1314. Zafiriou, O.C., 1973. Petroleum hydrocarbons in Narragansett Bay II. Chemical and isotopic analyses. Est. Coast. Mar. Sci. 1, 81–87.
Contents lists available at ScienceDirect
Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul
Viewpoint
‘‘Unresolved Complex Mixture’’ (UCM): A brief history of the term and moving beyond it John W. Farrington a,⇑, James G. Quinn b a b
MS#8, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA Graduate School of Oceanography, University of Rhode Island, 215 South Ferry Road, Narragansett, RI 02882-1197, USA
a r t i c l e
i n f o
Article history: Received 6 March 2015 Revised 17 April 2015 Accepted 18 April 2015 Available online 29 April 2015 Keywords: Unresolved Complex Mixture UCM Oil pollution
a b s t r a c t The term ‘‘Unresolved Complex Mixture’’ (UCM) has been used extensively for decades to describe a gas chromatographic characteristic indicative of the presence of fossil fuel hydrocarbons (mainly petroleum hydrocarbons) in hydrocarbons isolated from aquatic samples. We chronicle the origin of the term. While it is still a useful characteristic for screening samples, more modern higher resolution two dimensional gas chromatography and gas chromatography coupled with advanced mass spectrometry techniques (Time-of-Flight or Fourier Transform-Ion Cyclotron Resonance) should be employed for analyses of petroleum contaminated samples. This will facilitate advances in understanding of the origins, fates and effects of petroleum compounds in aquatic environments. Ó 2015 Elsevier Ltd. All rights reserved.
Advances in application of parallel chromatographic methods and three different types of mass spectrometry (MS) (e.g. Gough and Rowland, 1990) and multidimensional gas chromatography (GC) (e.g. Frysinger et al., 2003) or two-dimensional GC coupled with time of flight MS (e.g. Booth et al., 2007) have at least partially resolved or essentially completely resolved the Unresolved Complex Mixture of hydrocarbons in petroleum samples and in several environmental samples from petroleum contaminated or oil spill contaminated and polluted environments. The extent of the partial or essentially complete resolution depends on molecular weight range and molecular type of compounds present, e.g. No. 2 fuel oils are essentially completely resolved, and some crude oils are partially resolved. These advances have stimulated another round of inquiries similar to those we have been asked numerous times during the past forty years about the origin of the term ‘‘Unresolved Complex Mixture’’ or UCM, a term still in use as one indicator of petroleum or fossil fuel pollution (e.g. Wang et al., 2015). To our knowledge and extensive literature research, the term, including the shorthand notation UCM, was first used in our paper Farrington and Quinn (1973a). At that time, we had no inkling of how extensively it would be used. We provide here a short account of the history of the term which has been used in hundreds, if not thousands, of scientific papers, chapters and technical reports since 1973, including numerous papers published in Marine Pollution Bulletin. ⇑ Corresponding author. Tel.: +1 508 274 1926. E-mail addresses: [email protected] (J.W. Farrington), [email protected] (J.G. Quinn). http://dx.doi.org/10.1016/j.marpolbul.2015.04.039 0025-326X/Ó 2015 Elsevier Ltd. All rights reserved.
One of us (JWF) was a Ph.D. student advised by the other (JGQ) at the Graduate School of Oceanography, University of Rhode Island 1968–1971. JWF’s Ph. D. Dissertation research initially focused in part on the use of lipid class compounds in sewage discharges to Narragansett Bay, R.I. USA as a potential means of tracking sewage inputs to the bay. One of the target classes of compounds selected for testing was the class n-alkanes. We knew from earlier research that n-alkanes with an odd over even carbon number predominance in the molecular weight range of 23–31 carbons chain length were predominant in land plants as constituents of the waxy coating on plants (Eglinton et al., 1962a,b). Marine organisms did not have such an n-alkane distribution, with odd over even carbon number predominance in a limited range of 22–31 carbon chain length. (Clark and Blumer 1967, among others). We set out sampling sewage discharge waters from a large municipal sewage treatment plant, surface sediments in Narragansett Bay and hard shell clams (Mercenaria mercenaria), extracting the lipid class compounds, and isolating several classes of lipids by column chromatography (CC), thin layer chromatography (TLC), and analyzing the hydrocarbon fraction by gas chromatography using a packed column in a temperature programmed gas chromatograph (GC) equipped with a flame ionization detector connected to a strip chart recorder. These were our first hydrocarbon analyses and we expected to see a series of resolved n-alkanes, pristane and phytane peaks as had been reported in the literature for sediments and marine organisms and which we had replicated with standard mixtures of n-alkanes. Instead we had a slowly rising slightly wiggling graph trace over time, with a few small peaks on top of this line that
30
J.W. Farrington, J.G. Quinn / Marine Pollution Bulletin 96 (2015) 29–31
gradually came back to the column bleed background of the GC column as the temperature program run ended (Fig. 1). We thought that JWF had done something wrong. Several extractions, isolations by CC, TLC, and GC analyses were repeated. Nothing changed and we were perplexed. The gas chromatograms were placed on a shelf, the TLC isolates were stored in vials in a refrigerator, and JWF got on with the fatty acid analyses which were also part of his dissertation research. A few months later a clue to what we were measuring in the gas chromatograms of the hydrocarbons was discovered in an ongoing literature search. JGQ required all his students to participate in a coordinated lab group literature search on topics of interest to our group, e.g. lipids, hydrocarbons, fatty acids, triacylglycerols. As part of this, JWF was searching Chemical Abstracts when he came across an abstract of a paper ‘‘Microbiological Alterations of Crude oil in the Reservoir’’ by J.C. Winters and J.A. Williams presented at a Symposium on Petroleum Transformations in Geological Environments of the Division of Petroleum Chemistry, Inc. of the American Chemical Society Meeting, September 7–12, 1969. The abstract in Chemical Abstracts was intriguing. That division of the ACS had published extended abstracts from the ACS meetings and we requested one from the authors by mailing a reprint request card, a common practice in those days. The extended abstract arrived within a few weeks. It contained figures with reproductions of the packed column gas chromatograms of the unaltered reservoir crude oil of the Bell Creek Formation on the border of Montana and Wyoming, and gas chromatograms of a transect of samples from the near surface reservoir of that formation which received a groundwater incursion with nutrients and oxygen. The former contained many resolved peaks of n-alkanes and branched alkanes superimposed on a broad rising and falling background signal. For the latter, the n-alkane peaks were much reduced or missing for the transect samples and isoprenoid alkanes were predominant and superimposed on the rising and falling broad background signal. The broad, non-descript rising and then and falling gas chromatogram signal was attributed by inference
to a naphthenic (mainly cycloalkanes) character to the biodegraded crude oil (Winters and Williams, 1969) It was an ‘‘aha’’ moment for us. Immediately we reasoned that our gas chromatograms of alkane hydrocarbons isolated from sewage effluents, surface sediments and hard shell clams were of biodegraded oil and/or lubricating oil (known to be mainly naphthenic in composition) being discharged via the sewage effluent (and perhaps other sources) to Upper Narragansett Bay. In hindsight, one could argue we should have expected chronic oil released via sewage effluents. However, our literature search in 1968 and 1969 had yielded many papers about measurements of total ‘‘grease and oil’’ – meaning animal fats and vegetable oils mainly from household and restaurant sources, and some specific analyses of fatty acids. Shortly thereafter, in 1970 a paper was published reporting the presence of No. 2 fuel oil components in edible shellfish as result of the Barge Florida No. 2 Fuel Oil spill on September 16, 1969 at the coast of West Falmouth in Buzzards Bay, Massachusetts, USA (Blumer et al., 1970). The gas chromatograms again contained the series of resolved or partially resolved peaks on top of the broad rising and falling detector signal. In that publication, Blumer et al. designated the phenomenon as the unresolved background. Blumer et al. (1970, 1973) and Blumer and Sass (1972) designated this signal the unresolved envelope of oil compounds. The term unresolved envelope seemed like a good term to us and JWF used it in his Ph. D. dissertation to describe attributes of our hydrocarbon gas chromatograms from several samples of sewage effluents, surface sediment samples, and hard shell clams obtained in Narragansett Bay. JWF took a position as a Postdoctoral Investigator in Max Blumer’s laboratory at Woods Hole Oceanographic Institution in July 1971. Throughout the remainder of 1971 and into 1972 JWF presented seminars and talks at various places and meetings during which he presented slides with the term ‘‘unresolved envelope’’ while preparing papers from his dissertation for publication. One paper (Farrington and Quinn, 1973b) was prepared, submitted,
Fig. 1. Packed column gas chromatograms of hydrocarbons isolated from Narragansett Bay surface sediments (left column) and Mercenaria mercenaria (right column). N–C22– alkane added as internal standard in the right column chromatograms. Stations F.P. and E. were in the Providence River area of Upper Narragansett Bay that received municipal and storm sewer discharges from municipal Providence R.I., Stations D and C were in the mid to upper reaches of Narragansett Bay. Charlestown Pond is a rural area and the control for the study. The chromatogram trace for the Charlestown Pond sample is the same as for the laboratory control and indicates the GC baseline for the temperature controlled GC analysis. (Figure reproduced with permission from Farrington and Quinn (1973a)).
J.W. Farrington, J.G. Quinn / Marine Pollution Bulletin 96 (2015) 29–31
and accepted for publication in which we used the term unresolved envelope as used by Blumer et al. (1970, 1973) and Blumer and Sass (1972). During JWF’ seminars and talks, the term ‘‘unresolved envelope’’ was criticized by some analytical chemists as not worthy of mention because we ‘‘had failed to resolve the compounds yielding the signal’’. We understood that concern, but thought that the signal should not be ignored and we believed we were in good company in that regard. Other critics did not like the term ‘‘envelope’’. Some remarked during a few seminars that an ‘‘envelope was something in which one mailed a letter’’. These criticisms led JWF to suggest that we use the term ‘‘Unresolved Complex Mixture’’, which would acknowledge we had not resolved the components of this complex mixture, and use the words ‘‘complex mixture’’ as noting the presence of the complexity of hydrocarbons found in fossil fuels such as crude oil and fuels and coal extracts. In reproductions of the gas chromatograms we used the short hand UCM to label the Unresolved Complex Mixture when it was present (Farrington and Quinn, 1973a). Fig. 1. Our only caveat that this might not be petroleum hydrocarbons was a concern that perhaps hydrocarbons biosynthesized by a very complex assemblage of microbes in sewage might yield the UCM signal. Discussion with Oliver C. Zafiriou, also in Max Blumer’s laboratory at that time, about that possibility led to additional analyses of hydrocarbons from a large several kg sediment sample from Upper Narragansett Bay/Providence River and a companion paper to our 1973a paper (Zafiriou, 1973). He reported radiocarbon (D14C) activity for hydrocarbons extracted and isolated from the sample of sediment indicating that the carbon in hydrocarbons of the UCM were 80–97% fossil, consistent with a fossil fuel source. This type of measurement for the radiocarbon (D14C) activity of hydrocarbons extracted from surface sediments was repeated a few years later for a sediment sample from the New York Bight Sewage Sludge Dump site (Farrington and Tripp, 1977) and more recently for samples of coastal sediments, road dust and urban atmospheric particulate samples with the result that 90% or greater of the carbon of the UCM was fossil carbon and therefore arguably from fossil fuel contamination/pollution (White et al., 2013). Professor Kurt Grob, a pioneer in analytical chemistry especially using glass capillary gas chromatography, took up a challenge from Dr. Max Blumer during the period 1973–74 and proceeded to almost completely resolve all the hydrocarbon components in a diesel oil (similar in molecular weight range to No. 2 Fuel Oil) into individual GC peaks using ingenious but time consuming glass capillary chromatography with 70 m columns, 3 h temperature programmed techniques, and transfer of several minute time portions of the first capillary GC column to a second glass capillary column for further separation (Grob, 1975). His methods were the forerunners of modern two dimensional GC analyses. Unfortunately, the time consuming nature of the methodology, about three or usually more hours per GC analysis, and the difficult art of preparing the fragile glass capillary columns, precluded routine analyses of oil contaminated samples by this methodology for several years. Identification and quantitative analyses of the major polycyclic aromatic hydrocarbons (PAH) from fossil fuels and pyrogenic sources in the aromatic hydrocarbon fraction of extracts of environmental samples proceeded in the interim years via probe distillation MS and GS–MS (e.g. Youngblood and Blumer, 1975; Hites and Biemann, 1975). Despite these advances, there are many aromatic hydrocarbons in the aromatic fraction UCM which were not identified and quantified. A very important study by Booth et al. (2007) found that several of the compounds contributing to the aromatic hydrocarbon UCM are toxic. Booth et al. noted that the potential for adverse effects from the UCM aromatic compounds had been overlooked.
31
The UCM signal may continue to be a screening tool for identifying samples containing complex mixtures of hydrocarbons in samples to become candidates for further analyses. However, when complex mixtures are identified, we call for the routine application of more modern analytical techniques such as multidimensional GC capable of resolving the components of the UCM, coupled with various types of mass spectrometry to identify these components and quantify concentrations (e.g. Gros et al., 2014). Simultaneously, it is important to gain a better understanding of the relationship between the identified compounds and mixtures of compounds, bioaccumulation potential and biological effects as pointed out by Booth et al. (2007). Acknowledgements John W. Farrington conceived of the idea of this Viewpoint article and led the writing. James G. Quinn added substantive comments and suggestions. Both authors approve submission of the manuscript. The authors have no substantive conflicts of interest that pertain to this article to disclose. This manuscript was selffunded. Both authors are formally retired. References Blumer, M., Souza, G., Sass, J., 1970. Hydrocarbon pollution of edible shellfish by an oil spill. Mar. Biol. 5, 195–202. Blumer, M., Sass, J., 1972. Indigenous and petroleum-derived hydrocarbons in a polluted sediment. Mar. Pollut. Bull. 396, 92–94. Blumer, M., Ehrhardt, M., Jones, J.H., 1973. The environmental fate of stranded crude oil. Deep Sea Res. 20, 239–259. Booth, A.M., Sutton, P.A., Lewis, A.C., Scarlett, A., Chau, W., Widdows, J., Rowland, S.J., 2007. Unresolved complex mixtures of aromatic hydrocarbons: thousands of overlooked persistent, bioaccumulative, and toxic contaminants in mussels. Environ. Sci. Technol. 41, 457–464. Clark, R.C., Blumer, M., 1967. Distribution of n-paraffins in marine organisms and sediment. Limnol. Oceanog. 12 (1), 79–87. Eglinton, G., Hamilton, R.J., Raphael, R.A., 1962a. Hydrocarbon constituents of the wax coatings of plant leaves: a taxonomic survey. Nature 193, 739–742. Eglinton, G., Gonzalez, A.G., Hamilton, R.J., Raphael, R.A., 1962b. Hydrocarbon constituents of the wax coatings of plant leaves: a taxonomic survey. Phytochemistry 1, 89–102. Farrington, J.W., Quinn, J.G., 1973a. Petroleum hydrocarbons in Narragansett Bay I: survey of hydrocarbons in sediments and clams (Mercenaria mercenaria). Est. Coast. Mar. Sci. 1, 71–79. Farrington, J.W., Quinn, J.G., 1973b. Petroleum hydrocarbons and fatty acids in wastewater effluents. J. Water Pollut. Control Fed. 45 (4), 704–712. Farrington, J.W., Tripp, B.W., 1977. Hydrocarbons in Western North Atlantic surface sediments. Geochim. Cosmochim. Acta 41, 1627–1641. Frysinger, G.S., Gaines, R.B., Xu, L., Reddy, C.M., 2003. Resolving the unresolved complex mixture in petroleum contaminated sediments. Environ. Sci. Technol. 37, 1653–1662. Grob, K., 1975. The glass capillary column in gas chromatography. A tool and a technique. Chromatographia 8 (9), 423–433. Gros, J., Reddy, C.M., Aeppli, C., Nelson, R.K., Carmichael, C.A., Arey, J.S., 2014. Resolving biodegradation patterns of persistent saturated hydrocarbons in weathered oil samples from the Deepwater Horizon disaster. Environ. Sci. Technol. 48 (3), 1628–1637. Gough, M.A., Rowland, S.J., 1990. Characterization of unresolved complex mixtures of hydrocarbons in petroleum. Nature 344, 648–650. Hites, R.A., Biemann, W.G., 1975. Identification of specific organic compounds in a highly anoxic sediment by gas chromatographic mass spectrometry and high resolution mass spectrometry. Adv. Chem. Series Issue 147, 188–201. Wang, M., Wang, C., Hu, X., Zhang, H., He, S., Lv, S., 2015. Distributions and sources of petroleum, aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) in surface sediments from Bohai Bay and its adjacent river, China. Mar. Pollut. Bull. 90, 88–94. White, H.K., Xu, L., Hartmann, P., Quinn, J.G., Reddy, C.M., 2013. Unresolved Complex Mixture (UCM) in coastal environments is derived from fossil sources. Environ. Sci. Technol. 47, 726–731. Winters, J.C., Williams, J.A., 1969. Microbiological alteration of crude oil in the reservoir. Extended Abstract Symposium on Petroleum Transformations in Geological Environments, The Division of Petroleum Chemistry, Inc. American Chemical Society. E22-31. Youngblood, W., Blumer, M., 1975. Polycyclic aromatic hydrocarbons in the environment: homologous series in soils and recent marine sediments. Geochim. Cosmochim. Acta 39, 1303–1314. Zafiriou, O.C., 1973. Petroleum hydrocarbons in Narragansett Bay II. Chemical and isotopic analyses. Est. Coast. Mar. Sci. 1, 81–87.