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3%0/12/1995 20.44 9163519357 ANNE M FARR PAGE 17 TABLE I PARAMETERS ASSEnED DURING EVALUATION OF PETROLEUM CONTAMINATION--Continued Paviarsseter Information provided Gasoline-range lsy&*carbons(C3-Cto)—Continued Aromatic hydrocarbons • Due to char high water solubilities,the relative concentration of BTEX compounds is (BTEX—benzene, proportional to the length of exposure to water(water washing) BTEX data can also be toluene,ethylbenune, used to determine die type of petroleum product and identify the source and Xylenes) Dye additives • Dyes are added to sonic gasolines in order to tell different grades apart Gasolmes typically appear to have a yellow-gold or peak-red color, aviation gasoline has a blue color Therefore,identification of the dye color aids in determining the type of gasoline released and the potential source Methyltemary butyl ether • Since about 1980,MTBE has been blended with hydrocarbons to produce reformulated (MTBE) gasolene, designed to reduce carbon monoxide and other atmospheric pollutants in automobile exhaust.Therefore,tete presence of MTBE indicates a reformulated gasoline and helps in source Identification. Lead alkyl compounds • Until rc=dy, lead alkyls were commonly added to gasoline as ani-knock agents Tetraethyl lead was used only after 1980. prior to that time tetramethyl lead. trimcthylethyl lead,dimethyldiethyl lead,and methyltnethyl lead were added There- fore,analysts for these compounds helps determine if the product was released before or after 1980 Ethylene&bromide a IDB was often added as a lead scavenger to gasolines containing leach alkyl anu-knock (EDB) agents The presence or absence of EDB,which is more soluble than the lead alkyls helps determine the extent of water washung. Stable Isotope ratios for • The 13CI12C ratio of a floating product can be compared with known potential sources carbon and hydrogen to aid m source tdeatiftcadon. • Stable isotope ratio comparison of free product collected from different ground-water monitoring wells may indicate wha6cr mix mg of different gasolines has occurred • Refined petroleum products have a 13cf"c ratio relatively close to that of the original crude oil Therefore, the 43C/l2C ratio may help identify the geographic area and geologic formation from which the crude oil originated,conwAuendy helping to identify the source which released the fuel Lubricating oils,Beating olls,l and crude ails Alkanes(paraffins) • The distribution of alkanes may be used to determine the degree of biodegradation A% shown in Figure 2a(page 1 10). biodegradation destroys the straight-chained hydro- carbons (n-alkana) first, leaving the branched-chained compounds (isoprenoids) if extensive biodegradation occurs,almost all of the normal and branched alkanes may be lost,leaving only the most tzarstant polycyclic alkanes(Figure 2b.page 1.10) The Hazardous Waste Coriolis 1z March/April 1993 1.7