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DELTA-13C VALUES OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) COLLECTED FROM TWO CREOSOTE-CONTAMINATED WASTE SITES
Citation:
Trust, B. A., C. A. Kelley, R B. Coffin, L. A. Cifuentes, AND J. G. Mueller. DELTA-13C VALUES OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) COLLECTED FROM TWO CREOSOTE-CONTAMINATED WASTE SITES. Presented at Variability of Isotope Compositions, Geological Society of America, New Orleans, LA, November 05, 1995.
Impact/Purpose:
Presentation
Description:
Groundwater samples were collected from the American Creosote Works (ACW) Superfund site in Pensacola, Florida in June and September 1994. Sampling wells were located along a transect leading away from the most contaminated area. PAHs were extracted from the groundwater samples with methylene chloride. Concentrations and delta 13C values of the individual PAH compounds were measured by gas chromatography/ion trap mass spectrometry/isotope ratio mass spectrometry (GC/ITMS/IRMS). Concentrations of all PAHs decreased by at least four orders of magnitude from the most contaminated to the least contaminated well; however, the delta 13C values of the compounds did not vary greatly across the wells. The majority of delta 13C values also did not differ between collection dates. The delta 13C values of the PAHs, averaged across all wells, ranged from -20.1 to -30.8 o/oo for the two collection dates. Groundwaters were also colllected from 13 wells (two depths per well) at a creosote-contaminated site in Gainesville, Florida in February, 1995. Sixteen PAHs were analyzed for concentration and 13C content. Similar to the results obtained at the ACW site, the wells at the Gainesville site had greater variabilities in individual PAH concentrations than in delta 13C values of those same compounds. For example, naphthalene varied in concentration from 1.5 to 8.5 ppm across the wells [average=4.6 plus or minus 2.2 ppm (n=15)]. The delta 13C values of naphthalene only varied from -23.8 to -24.9 o/oo across the wells [average=-24.3 plus or minus 0.3 o/oo (n=15)]. The delta 13C values of all the PAHs, averaged across all wells, ranged -19.9 to -25.0 o/oo. Results indicate that delta 13C values of PAHs are conserved as the compounds migrate through groundwater aquifers.