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Unresolved complex mixture (also UCM or hump) is a feature frequently observed in gas chromatographic (GC) data of crude oils and extracts from organisms exposed to oil.〔Gough, M. A. & Rowland, S. J. Characterization of Unresolved Complex-Mixtures of Hydrocarbons in Petroleum. Nature 344, 648-650 (1990).〕 The reason for the UCM hump appearance is that GC cannot resolve and identify a significant part of the hydrocarbons in crude oils. The resolved components appear as peaks while the UCM appears as a large background/platform. In non-biodegraded oils the UCM may comprise less than 50% of the total area of the chromatogram, while in biodegraded oils this figure can rise to over 90%. UCMs are also observed in certain refined fractions such as lubricating oils 〔 and references therein. One reason why it is important to study the nature of UCMs is that some have been shown to contain toxic components,〔Rowland, S., Donkin, P., Smith, E. & Wraige, E. Aromatic hydrocarbon "humps" in the marine environment: Unrecognized toxins? Environmental Science & Technology 35, 2640-2644 (2001).〕〔Donkin, P., Smith, E. L. & Rowland, S. J. Toxic effects of unresolved complex mixtures of aromatic hydrocarbons accumulated by mussels, Mytilus edulis, from contaminated field sites. Environmental Science & Technology 37, 4825-4830 (2003).〕〔Booth, A. M. et al. Unresolved Complex Mixtures of Aromatic Hydrocarbons: Thousands of Overlooked Persistent, Bioaccumulative, and Toxic Contaminants in Mussels. Environ. Sci. Technol. 41, 457-464 (2007).〕〔Scarlett, A., Galloway, T. S. & Rowland, S. J. Chronic toxicity of unresolved complex mixtures (UCM) of hydrocarbons in marine sediments Journal of Soils & Sediments 7, 200-206 (2007).〕〔Scarlett, A., Rowland, S. J., Galloway, T. S., Lewis, A. C. & Booth, A. M. Chronic sublethal effects associated with branched alkylbenzenes bioaccumulated by mussels. Environmental Toxicology and Chemistry 27, 561-567 (2008).〕〔Booth, A., Scarlett, A., Lewis, C. A., Belt, S. T. & Rowland, S. J. Unresolved Complex Mixtures (UCMs) of Aromatic Hydrocarbons: Branched Alkyl Indanes and Branched Alkyl Tetralins are present in UCMs and accumulated by and toxic to, the mussel Mytilus edulis. Environ Sci Technol. 42, 8122-8126 (2008).〕〔Scarlett, A., Dissanayake, A., Rowland, S. J. & Galloway, T. S. Behavioral, physiological, and cellular responses following trophic transfer of toxic monoaromatic hydrocarbons. Environmental Toxicology and Chemistry 28, 381-387 (2009).〕〔Tollefsen, K. E., Harman, C., Smith, A. & Thomas, K. V. Estrogen receptor (ER) agonists and androgen receptor (AR) antagonists in effluents from Norwegian North Sea oil production platforms. Marine Pollution Bulletin 54, 277-283 (2007).〕〔Smith, E., Wraige, E., Donkin, P. & Rowland, S. Hydrocarbon humps in the marine environment: Synthesis, toxicity, and aqueous solubility of monoaromatic compounds. Environmental Toxicology and Chemistry 20, 2428-2432 (2001).〕 but only a small range of known petrogenic toxicants, such as the USEPA list of 16 polycyclic aromatic hydrocarbons (PAHs), tend to be routinely monitored in the environment. Analysis of the hydrocarbon fraction of crude oils by gas chromatography (GC) reveals a complex mixture containing many thousands of individual components.〔Sutton, P. A., Lewis, C. A. & Rowland, S. J. Isolation of individual hydrocarbons from the unresolved complex hydrocarbon mixture of a biodegraded crude oil using preparative capillary gas chromatography. Organic Geochemistry 36, 963-970 (2005).〕 Components that are resolved by GC have been extensively studied e.g.〔Killops, S. D. & Killops, V. J. An introduction to organic geochemistry (Longman, Harlow, England, 1993).〕 However, despite the application of many analytical techniques the remaining components have, until very recently, proved difficult to separate due to the large numbers of co-eluting compounds. Gas chromatograms of mature oils have prominent n-alkane peaks which distract attention from the underlying unresolved complex mixture (UCM) of hydrocarbons often referred to as the ‘hump’. Processes such as weathering and biodegradation result in a relative enrichment of the UCM component by removal of resolved components and the creation of new compounds.〔Peters, K. E., Walters, C. C. & Moldowan, J. M. The biomarker guide: Volume 1, Biomarkers and Isotopes in the Environment and Human History (Cambridge University Press, Cambridge, England, 2005).〕 It has been shown that both resolved and unresolved components of oils are subject to concurrent biodegradation,〔 i.e. it is not a sequential process, but due to the recalcitrant nature of some components, the rates of biodegradation of individual compounds greatly varies. The UCM fraction often represents the major component of hydrocarbons within hydrocarbon-polluted sediments 〔 (see reference therein) and biota e.g.〔〔〔Fowler, S. W., Readman, J. W., Oregioni, B., Villeneuve, J. P. & McKay, K. Petroleum-Hydrocarbons and Trace-Metals in Nearshore Gulf Sediments and Biota before and after the 1991 War - an Assessment of Temporal and Spatial Trends. Marine Pollution Bulletin 27, 171-182 (1993).〕〔Colombo, J. C. et al. Oil spill in the Rio de la Plata estuary, Argentina: 1. Biogeochemical assessment of waters, sediments, soils and biota. Environmental Pollution 134, 277-289 (2005).〕 A number of studies has now demonstrated that aqueous exposure to components within the UCM can affect the health of marine organisms,〔〔〔〔〔〔〔 including possible hormonal disruption,〔 and high concentrations of environmental UCMs have been strongly implicated with impaired health in wild populations.〔〔〔Crowe, T. P., Smith, E. L., Donkin, P., Barnaby, D. L. & Rowland, S. J. Measurements of sublethal effects on individual organisms indicate community-level impacts of pollution. Journal of Applied Ecology 41, 114-123 (2004).〕〔Guerra-Garcia, J. M., Gonzalez-Vila, F. J. & Garcia-Gomez, J. C. Aliphatic hydrocarbon pollution and macrobenthic assemblages in Ceuta harbour: a multivariate approach. Marine Ecology-Progress Series 263, 127-138 (2003).〕 ==Weathering and biodegradion of oils within the marine environment== Environmental UCMs result from highly degraded petroleum hydrocarbons and once formed they can stay largely unchanged in sediments for many years. For example, in 1969 a diesel oil spill contaminated saltmarsh sediment within Wild Harbor River, US; by 1973 only a baseline hump was observed, which remained largely unchanged within the anaerobic sediment for 30.〔Reddy, C. M. et al. The West Falmouth oil spill after thirty years: the persistence of petroleum hydrocarbons in marsh sediments. Environmental Science & Technology 36, 4754-4760 (2002).〕 In a study of the potential for UCM-dominated oil to be further degraded, it was concluded that even using bacteria specifically adapted for complex UCM hydrocarbons in conjunction with nutrient enrichment, biodegradation rates would still be relatively slow.〔McGovern, E. (Marine Institute Fisheries Research Centre, Dublin, 1999).〕 Bacterial degradation of hydrocarbons is complex and will depend on environmental conditions (e.g. aerobic or anaerobic, temperature, nutrient availability, available species of bacteria etc.). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Unresolved complex mixture」の詳細全文を読む スポンサード リンク
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