ENVR 38 |
| Substantial amounts of polar organic materials have been quantified in the total petroleum hydrocarbon (TPH) extracts from some petroleum-contaminated groundwaters. Analyses have shown that the chromatographic nature of the polar material presents itself as a classical ‘hump' or unresolved complex mixture (UCM), similar to that associated with the aliphatic and aromatic organic material comprising fresh diesel-range petroleum products. In this study, groundwater TPH from a well characterized petroleum-contaminated aquifer has been analyzed using column fractionation techniques, gas chromatography and comprehensive two-dimensional gas chromatography (GCxGC). The results demonstrate that the operationally-defined TPH is polar (i.e., not adsorbed or colloidal) and can account for >80% of the total extract. Analysis of source hydrocarbon mixtures demonstrates that a majority of the polar material is not derived directly from the original product, implying post-depositional alteration processes. The GCXGC analysis of the polar material suggests a structural relationship to the complex mixture of cyclo-alkanes identified in fresh diesel mixtures. Results from GCXGC-TOF mass spectrometry further suggest microbial oxidation of the original hydrocarbons as a potential mechanism for the production of these polar compounds. These results alter our understanding of petroleum-contaminated groundwater fate and transport. They may also significantly affect our perspectives on environmental toxicology and the interaction between petroleum contamination and beneficial water quality. By demonstrating that organic material present in petroleum-contaminated groundwater may be fundamentally different from our existing conceptual models, this work requires us to review our understanding of the biogeochemical processes associated with biodegradation and re-examine the extent to which this new information may affect existing predictive environmental models. |
|
Symposium Honoring Dr. Walter Giger
8:30 AM-12:15 PM, Monday, August 20, 2007 Boston Park Plaza -- Stanbro Rm, Oral
Division of Environmental Chemistry |