Oceanography The Official Magazine of
The Oceanography Society
Volume 29 Issue 03

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Volume 29, No. 3
Pages 50 - 63


Chemical Composition of Macondo and Other Crude Oils and Compositional Alterations During Oil Spills

Edward B. Overton Terry L. WadeJagoš R. RadovićBuffy M. MeyerM. Scott MilesStephen R. Larter
Article Abstract

Crude oils are some of the most complex and diverse organic mixtures found in nature. They contain thousands of different compounds belonging to several compound classes, with the main ones being hydrocarbons and their heteroatom (N, S, and O)-containing analogs, called non-hydrocarbons. In general, all crude oils contain the same types of chemical structures, but these compounds can be in highly variable proportions in crude oils drawn from different reservoir conditions and locations. Both the types of compounds and their respective quantities change rapidly once the crude oil is spilled into the environment, making the circumstances associated with every spill unique. In general, smaller and lower molecular weight oil compounds are more susceptible to processes such as evaporation, dissolution, and biodegradation, while the heavier, more hydrophobic compounds tend to adhere to living organisms or particulates and persist. The presence of certain compounds, such as PAHs (polycyclic aromatic hydrocarbons), also determines the acute and chronic toxicity of the spilled oil. Natural processes can degrade virtually all compounds in crude oils, with aerobic oxidation proceeding much faster than anaerobic degradation, although not all crude oil components are degraded with the same speed. The environmental fate and effects of crude oil degraded by biodegradation and photooxidation are yet to be fully determined. Due to the submarine and offshore setting of the Macondo well blowout, components of the spilled oil were distributed throughout the marine environment—water column, sediments, surface waters, and the coast. The light and nonviscous nature of Macondo crude oil favored its removal through natural degradation, evaporation, dissolution, and dispersal processes. In spite of the unprecedented quantities of oil that spilled, the final fate and effects of the oil, the more recalcitrant fractions of Macondo oil, and the oil weathering products have not been totally elucidated. Responders with knowledge of the physical properties of the Macondo oil executed their preplanned response efforts and kept a majority of the oil from reaching the more sensitive coastal areas.


Overton, E.B., T.L. Wade, J.R. Radović, B.M. Meyer, M.S. Miles, and S.R. Larter. 2016. Chemical composition of Macondo and other crude oils and compositional alterations during oil spills. Oceanography 29(3):50–63, https://doi.org/10.5670/oceanog.2016.62.


Aeppli, C., R.K. Nelson, J.R. Radović, C.A. Carmichael, D.L. Valentine, and C.M. Reddy. 2014. Recalcitrance and degradation of petroleum biomarkers upon abiotic and biotic natural weathering of Deepwater Horizon oil. Environmental Science & Technology 48:6,726–6,734, https://doi.org/10.1021/es500825q.

Albaigés, J., J.M. Bayona, and J.R. Radović. 2016. Photochemical effects on oil spill fingerprinting. Pp. 917–959 in Standard Handbook of Oil Spill Environmental Forensics, 2nd ed. S. Stout and Z. Wang, eds, Academic Press, Burlington, MA.

Atlas, R.M. 1981. Microbial degradation of petroleum hydrocarbons: An environmental perspective. Microbiological Reviews 45(1):180–209.

Atlas, R.M., and T.C. Hazen. 2011. Oil biodegradation and bioremediation: A tale of the two worst spills in U.S. history. Environmental Science & Technology 45:6,709–6,715, https://doi.org/10.1021/es2013227.

Atlas, R.M., D.M. Stoeckel, S.A. Faith, A. Minard-Smith, J.R. Thorn, and M.J. Benotti. 2015. Oil biodegradation and oil-degrading microbial populations in marsh sediments impacted by oil from the Deepwater Horizon well blowout. Environmental Science & Technology 49(14):8,356–8,366, https://doi.org/10.1021/acs.est.5b00413.

Bahreini, R., A.M. Middlebrook, C.A. Brock, J.A. de Gouw, S.A. McKeen, L.R. Williams, K.E. Daumit, A.T. Lambe, P. Massoli, M.R. Canagaratna, and others. 2012. Mass spectral analysis of organic aerosol formed downwind of the Deepwater Horizon oil spill: Field studies and laboratory confirmations. Environmental Science & Technology 46:8,025−8,034, https://doi.org/10.1021/es301691k

Beyer, J., H.C. Trannum, T. Bakke, P.V. Hodson, and T.K. Collier. In press. Environmental effects of the Deepwater Horizon oil spill: A review. Marine Pollution Bulletin, https://doi.org/10.1016/​j.marpolbul.2016.06.027.

Boehm, P.D., K.J. Murray, and L.L. Cook. 2016. Distribution and attenuation of polycyclic aromatic hydrocarbons in Gulf of Mexico seawater from the Deepwater Horizon oil accident. Environmental Science & Technology 50(2):584–592, https://doi.org/10.1021/acs.est.5b03616.

Daling, P.S., F. Leirvik, I.K. Almas, P.J. Brandvik, A.L. Hansen, and M. Reed. 2014. Surface weathering and dispersibility of Macondo crude oil. Marine Pollution Bulletin 87:300–310, https://doi.org/10.1016/j.marpolbul.2014.07.005.

England, W.A., A.S. Mackenzie, D.M. Mann, and T.M. Quigley. 1987. The movement and entrapment of petroleum fluids in the subsurface. Journal of the Geological Society 144:327–347, https://doi.org/10.1144/gsjgs.144.2.0327.

GESAMP (Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection). 2007. Estimates of Oil Entering the Marine Environment from Sea-Based Activities. Representative Study GESAMP No. 75, London, UK, 96 pp. 

Head, I.M., D.M. Jones, and S.R. Larter. 2003. Biological activity in the deep subsurface and the origin of heavy oil. Nature 426:344–352, https://doi.org/10.1038/nature02134

Kennicutt, M.C., J.M. Brooks, R.R. Bidigare, R.R. Fay, T.L. Wade, and T.J. McDonald. 1985. Vent-type taxa in a hydrocarbon seep region on the Louisiana slope. Nature 317:351–353, https://doi.org/10.1038/317351a0.

Larter, S.R., and I.M. Head. 2014. Oil sands and heavy oil: Origin and exploitation. Elements 10(4):277–283, https://doi.org/10.2113/gselements.10.4.277.

Liu, Y., and E.B. Kujawinski. 2015. Chemical composition and potential environmental impacts of water-soluble polar crude oil components inferred from ESI FT-ICR MS. PLoS ONE 10(9), e0136376, https://doi.org/10.1371/journal.pone.0136376

NAS (National Academy of Sciences). 2003. Oil in the Sea III: Inputs, Fates, and Effects. National Academies Press, Washington, DC, 280 pp. 

Overton, E.B., J.L. Laseter, S.W. Mascarella, C. Raschke, I. Nuiry, and J.W. Farrington. 1980a. Photochemical oxidation of IXTOC I oil. Pp. 341–383 in Proceedings of Symposium on Preliminary Results from the September 1979 Researcher/Pierce IXTOC I Cruise. Key Biscayne, Florida, June 9–10, 1980, NOAA Office of Marine Pollution Assessment, Boulder, CO. 

Overton, E.B., L.V. McCarthy, S.W. Mascarella, M.A. Maberry, S.R. Antoine, J.W Farrington, and J.L. Laseter. 1980b. Detailed chemical analysis of IXTOC I crude oil and selected environmental samples from the Researcher and Pierce cruises. Pp. 439–495 in Proceedings of Researcher/Pierce IXTOC I Symposium. Key Biscayne, Florida, June 9–10, 1980, NOAA Office of Marine Pollution Assessment, Boulder, CO.

Patel, J.R., E.B. Overton, and J.L. Laseter. 1979. Environmental photooxidation of dibenzothiophenes following the Amoco Cadiz oil spill. Chemosphere 8:557–561, https://doi.org/​10.1016/0045-6535(79)90102-4.

Peters, K.E., C.C. Walters, and J.M. Moldowan. 2005. The Biomarker Guide: Biomarkers and Isotopes in the Environment and Human History, vol. 1, 2nd ed. Cambridge University Press, Cambridge, UK, 471 pp.

Prince, R.C., D.L. Elmendorf, J.R. Lute, C.S. Hsu, C.E. Haith, J.D. Senius, G.J. Dechert, G.S. Douglas, and E.L. Butler. 1994. 17α(H),21β(H)-hopane as a conserved internal marker for estimating the biodegradation of crude oil. Environmental Science & Technology 28:142–145, https://doi.org/10.1021/es00050a019.

Prince, R.C., and C.C. Walters. 2007. Biodegradation of oil hydrocarbons and its implications for source identification. Pp. 349–379 in Oil Spill Environmental Forensics: Fingerprinting and Source Identification. Z. Wang and S.A. Stout, eds, Academic Press, Burlington, MA. 

Radović, J.R., C. Aeppli, R.K. Nelson, N. Jimenez, C.M. Reddy, J.M. Bayona, and J. Albaigés. 2014. Assessment of photochemical processes in marine oil spill fingerprinting. Marine Pollution Bulletin 79(1–2):268–277, https://doi.org/10.1016/​j.marpolbul.2013.11.029.

Reddy, C.M., J.S. Arey, J.S. Seewald, S.P. Sylva, K.L. Lemkau, R.K. Nelson, C.A. Carmichael, C.P. McIntyre, J. Fenwick, G.T. Ventura, and others. 2011. Composition and fate of gas and oil released to the water column during the Deepwater Horizon oil spill. Proceedings of the National Academy of Science of the United States of America 109:20,229–20,234, https://doi.org/10.1073/pnas.1101242108.

Speight, J.G. 2006. The Chemistry and Technology of Petroleum, 4th ed. CRC Press, Boca Raton, FL, 980 pp. 

Snowdon, L.R, J.K. Volkman, Z. Zhang, G. Tao, and P. Liu. 2016. The organic geochemistry of asphaltenes and occluded biomarkers. Organic Geochemistry 91:3–15, https://doi.org/10.1016/​j.orggeochem.2015.11.005

Thominette, F., and J. Verdu. 1984. Photo-oxidative behavior of crude oils relative to sea pollution: Part II. Photo-induced phase separation. Marine Chemistry 15(2):105–115, https://doi.org/​10.1016/0304-4203(84)90010-0.

Wade, T.L., J.L. Sericano, S.T. Sweet, A.H. Knap, and N.L. Guinasso Jr. 2016. Spatial and temporal distribution of water column total polycyclic aromatic hydrocarbons (PAH) and total petroleum hydrocarbons (TPH) from the Deepwater Horizon (Macondo) incident. Marine Pollution Bulletin 103:286–293, https://doi.org/10.1016/j.marpolbul.2015.12.002.

Wang, Z., and M.F. Fingas. 2003. Development of oil hydrocarbon fingerprinting and identification techniques. Marine Pollution Bulletin 47:423–452, https://doi.org/10.1016/S0025-326X(03)00215-7.

Wang, Z., M.F. Fingas, E.H. Owens, L. Sigouin, and C.E. Brown. 2001. Long-term fate and persistence of the spilled Metula oil in a marine salt marsh environment: Degradation of petroleum biomarkers. Journal of Chromatography A 926:275–290, https://doi.org/10.1016/S0021-9673(01)01051-2.

Yen, T.F., and G.V. Chilingarian, eds. 2000. Asphaltenes and Asphalts, 2. Elsevier Science, Amsterdam, Netherlands, 644 pp.

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