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IM <br /> gLssgOWN <br /> _ .+. .' •• P gT`, S dy y; »+si <br /> Mg, <br /> Y <br /> £$^ <br /> i <br /> 66-15 <br /> :Un OI15 <br /> Natural acosystems have canzzdzrable exposure CO petroleum <br /> hydrocarbons from natural emissions. accidental contamination ination to oil spills and storage tank leaks. and dellberate applicatiore, their <br /> in waste disposal acti.icies such as loance. Numerous ming: <br /> biodegradation is of environmental iaaarcanc ydroca bons and oseveral <br /> observed the biodegradation of petroleum by <br /> extensive reviews and reports are availaobfle petroleum�Sydraearbon- <br /> 2253). hn extensive and diverse group <br /> degrading bacteria and fungi are widely distributed in the environment. <br /> ny <br /> Although the microbiata of most non-concamin aeiens ted i the iaddition Is include aof. <br /> naturally occurring hydrocaroorc-degrading p p <br /> petroleum selectively enriches that sector able to adapt and utilize <br /> encal factor <br /> the new substrate. Other environta <br /> factors <br /> s ox•� to haven ande moderate <br /> effect on biodegradability are availabi�ity yg <br /> Chapter 6k for a more ddtailed <br /> temperatures. The reader is referred to �apdraearbons. <br /> summary of the biodegradation os petrol.um by <br /> The qualitative hvdrocar4an content o£ petroleum mixtures Largely <br /> determines their degradability. In general, microorgarisma zxhibit <br /> decreasing abi'_ity to degradeIC nyrtally nmare rrapidlvs biodegraaed with increasing <br /> Chain length; aromatics are g <br /> alkanes. The composition of diesel oil suggests chat some of the <br /> aromatic the high <br /> species lilt be b degradable: biodegradation <br /> esencr. resid al oils will <br /> .molecular weight aromatics expected to be p <br /> be slower (23?9). <br /> radation of Che petroleum hydrocarbons <br /> In summary, biodeg <br /> comprising diesel and fuel oils may are occur under conditions favorablto <br /> e <br /> for microbial activity and when fuel compobnentlimitedreely and/eraislowe in <br /> the microorganisms. Degradation may lox H. low temperatures. <br /> envirorments 'with few degrading organisms, p <br /> and high salieni[a (e g. . arctic <br /> statenvironmeat t )under Optimum. It should bconditi ns. <br /> that WalY.er _� net expected to occur except <br /> zonal and complete biodegradation !,sfp <br /> possibly over an extremely long time period. <br /> 66.2.3 Primary Routes of Exposure from Soil/Ground-water Systems <br /> oils <br /> The above discussion of fate path w�airsucemponencs t:ary in pure ltheir <br /> 'nave low vapor pressure but chat ;cry strongly <br /> volatility from water. lvtvclicmaromatic Ivdrocarbons ponents are strongly in feel oils have <br /> sorbed to soil. The p while the <br /> a moderate or high potential for bioaccumula'.:oov otpncial for <br /> longer-chain aliphatic <br /> compounds have lest that the various <br /> bicaccumuiation. These Face i characteristics ocentialgexposure pachways. <br /> • components may have somewhat different p <br /> �• fuel oils from a disposal site or spill would <br /> Volatilization of <br /> noc be expected to result in significant inhalation exposures to <br /> workers or residents in the area. Gravt r: would tend to car:': bulk <br /> quantities of tae oil 'down cowards the tater table leaving only a <br /> 6/87 <br />