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10/12/1995 20.44 9163519357 ANNE M PARR PAGE 16 0muos of the major elements) appear in the altered by several physical and biological normal) alkanes, 2) saturated n-alkanes, refined product.'these"tracers- may allow proccases that occur in soil or natural waters 3) volatile aromatic hydrocarbons floating products on ground water or heavier (e S,ground water.rivers,etc} These pro- (BTF.7q, and 4)branched-chain(iso)and (semtvolable) hydrocarbons extracted from cesses, which remove the most volatile and cyclic (riaphthenAL) hydrocarbons. The 3ml or grouted water to be traced back to their soluble compound& must be taken into ac- end products of biodegradauon are usu- origin count during an investigation ally organic acids, such rs acme acid or • Evaporaden--Due to their higher vola- phenols Chemical Additives Neta unties, gasoline hydrocarbons are roost • Mlgrarwn--When a gas or liquid mi- Identify Prodec#s significantly affected by evaporation. grates through soil or ground water, dif- Refinenes often add chemicals to petro- which causes die inuncdiate loss of com- fusional alteration may occur.causing the leum products before they are distributed, pounds up to about Ca and continual loss most volaUk And lowest molecular weight Then include to about Q. Gasoline evaporation is compounds. (e g . hydrogen. helium • Dyes typically added to gasoline(yellow greatest when it is exposed at the ground urethane)to escape more rapidly In addi- or red)and aviation gas(blue)to help tell surface; however, evaporation may also tion, some components may adsorb onto them apart, occur in the viidose(unsaturated)zone if fide-grained sediments (such as `:lays) the soil is porous and vapors can escape during migration.Finally,some very mac- e Detergents to maintain engine cleanbtim, ttve compounds may be altered during • Water warhiAg—Depending on their migration.For instance,hydrogen sulfide • Antioxidant preservatives, solubilities. hydrocarbons, detergents may either react with minerals in the soil • Methyiterthary butyl ether(NME)in re- MTBE. and dyes may be removed from or be oxidized to 5,ullunc ai-td by oxygen- formulated gasoline. petrokum products orcnidc oil when they saturated surface waters that nugratc tato are exposed to water The highera constit- the soil • Methanol or ethanol in some reformulated uent's solubility,the faster it will solubi- gasolines.and !are to water For example. the atorAanc • Miring-13orizonral arid vertncai mixing hydrocarbons(BTIX--benzene,toluene, of contamirrsnts from adjacent pollutant • Lead alkyls(anti-knock agents)and lead releases may occur in the subsurface en- scavengers added to gasoline in the page. ethylbenzene, and xylenes) will be viroament. washed out by water over ame due to their Analysis of these components can be wed relatively high solubiliues to differentiate one fuel type from another and determine the sources of contamination. • 16wd09radatwn--Due to die c col'- 6GC's Forensic Approach tem petroleum and its refined products arc Hydrocarbon Composition May biodegraded by microorganisms in soil In order to conduct a foreTwic invesuga- Be Changed by Raterat Proesne3 and water Swung with the most easily tion,GGC assesses a number of parameters. oiudaed-biodegradation causes oxldanon sucb as diose listed in Table 1 Different i Once petroleum products ate released into of hydrocarbon connstituem in the follow- parameters air; assessed for gaaaline-range , the cnvtronmeni, they may be chemically ing order 1)unisatsuated straight-chain(or hydrocarbons (carbon chain numbers from TABLE I PARAMETERS ASSESSED DURING EVAI.UMON OF PETROLEUM CONTAMINATION Parnmeur Infornwaon provided Gasoline-range hydrocrtrbotss(C3-Clo) Individual gaseous a Analysis of Cl to Cg hydrocarbons aids in identifying the type of gasoline released and hydrocarbons in the potential sources Ci-Cs range Volatile hydrocarbons in • C3 to Cio hydrocarbon data are used to calculate the relative proportion of each the C3-Clo range idenufied hydrocarbon and the bulk composition in terms of the four major hydrocarbon families (n-alkanes. branched or iso-alkanes cyclic alkanes and aromauc hydro- carbons) Graphic representation of this data can be used to distinguish one type of tuel from another(Figure 1,page 19) Z.6 The Ham rdows Wastes Cowultant.-March/April 1993