Laserfiche WebLink
40 r f` <br /> with the soil sampling results A groundwater benzene plume map is presented on <br /> iFigure 6 <br /> Chromatograph Analysis <br /> The laboratory instrument used to analyze these soil and groundwater samples is known as <br /> a gas chromatograph. It operates by physically separating specific chemical compounds <br /> based on individual physical characteristics such as temperature and pressure A graph is <br /> produced of the time required to volatilize (separate) each of the individual compounds <br /> contained within the sample This graph is often referred to as the "fingerprint" of the <br /> sample, because its shape is unique to that particular sample <br /> Figures 7 and 8 present chromatographs for the soil samples collected from a depth of 25 <br /> and 26 feet from SV1 and SV6, respectively These chromatograph show distinct differ- <br /> ences in the composition of the petroleum hydrocarbons contained within each of these <br /> samples <br /> The SV1 chromatograph (Figure 7) is typical of the chromatographs from the other soil <br /> samples collected at SV2 through SVS, SV7 and SVS (See Appendix S) SV1 contains a <br /> higher percentage of hydrocarbon compounds from the "heavier" or higher boiling point <br /> portion of the spectrum, than the "lighter" or lower boiling point end This chromatograph <br /> pattern or "fingerprint" may be an indication of "aged" gasoline, where the lighter, more <br /> volatile constituents have volatilized and/or degraded over time and are no longer present <br /> in as high a concentration <br /> On the other hand, the SV6 chromatograph (Figure 8) is somewhat different than all the <br /> other chromatographs The chromatograph generally indicates the presence of <br /> constituents with lower boiling points The peak at 11 minutes, representative of an <br /> particular compound, does not appear on the chromatographs from the other boreholes <br /> o� .osA94e rt�x 8 940549 00 <br /> Z a19 ao <br />