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Wir <br /> . <br /> o- <br /> iucL OILS <br /> 66.15 <br /> Natural ecosystems <br /> hydrocarbons from have considerable exposure to <br /> ail spills and storage taakmleaks ns, ojeum <br /> atridental contamination at rough <br /> in waste disposal and deliberate a through <br /> act_•:hies such as application to Land <br /> biodegradation' is ac e[tvirortxental land-farming' therefore <br /> observed tl-le biodegradation of importance. Numerous au their <br /> exeenaive petroleum hydreca.cbons• hors have <br /> reviews and reports are available and several <br /> 2253). An extensive and diverse (1846,2252,x255, <br /> 2249. <br /> degradigroup of petroleumhydrocarbon- <br /> ng bacteria and fungi are widely distributed in the environment. <br /> Although the microbiota of most non-concaminaced soils include <br /> naturally environment. <br /> Petroleum occurring hydrocarbon-degrading populations, many <br /> selectively enriches chat sector able to adapt andiuc,, of <br /> effecthe new substrate. Other environmental factors shown to have <br /> effect on biodegradability -lize <br /> temperatures. are availability of o a =a- <br /> t <br /> The reader is referred to Chapter 64 for a more moderate <br /> summary of rhe biodegradation of <br /> Petroleum hydroearbons. <br /> The eualitactve hydrocarbon content of petroleum mixtures <br /> retermines :heir degradability. largely <br /> g obiiLty <br /> decreasing In general, microorganisms exhibit <br /> - Co degrade aliphatic hydrocarbons with increasing <br /> .help Length; aromatics are <br /> alkanes. The composition of generally diesela Z rsu rapidLI, biodegraded than <br /> aromatic species •.rill be biodegradable; bi de ria chat some <br /> molecular w o£ the <br /> eight aromatics expected co be present inMresidual ails will <br /> on of zhe high <br /> he slower (2339) . <br /> In susmmarv, biodegradation <br /> comprising diesel and of the petroleum hvdracarbons <br /> for microbi,; fuel oils may occur under conditions Favorable <br /> L accivicv and when fuel components are freely available to <br /> the microorganisms. g <br /> environments •with Degradation nav be limited and/or slow <br /> and high s fes'' degrading organisms, low in <br /> B alinicv (e• pH, low temperatures, <br /> that Walker e[ a g. , arctic environments), It should be mentioned <br /> to[al and (2257) stare chat even under optimum conditions. <br /> complete biodegradat <br /> Possibly over an extremely Long ion Ls not expected ro occur except <br /> time period. <br /> 66.2,3 Primary Rouces of Exposure from Soil/Ground-war.er Svstems <br /> The above discussion of face pachways suggests [hoc pure csseL oils <br /> have low Vapor <br /> volacilttr pressure but that their components :•ary <br /> from water. The components are scrongly or to their <br /> sorbed to soil. The o ' ery strop L <br /> d ,mode p Lvcyclic aramat' g <br /> .r .c Y <br /> a[e hydro <br /> or high aotential for Sioaccumulat,on. a chile have <br /> � .anger-gain <br /> biaaccumular aliphatic compounds have <br /> low ton. These Ea-.e characteristics suggest _Pace-h�LLl a far <br /> camponen[s may nave SMewhac different potential exposure pathways, <br /> = riaus <br /> Vola expect clan of fuel oils from a disposal si[e or spill would <br /> not be expected to <br /> workers or residents result in significant inhalation exposures to <br /> quan[_eics of t5e nil�do«st tthe aw Cravtt.r would tend ea carr-, bulk <br /> ards the water tab Le Leaving only a <br /> 6/87 <br />