Use of Advanced Tools to Measure the Composition of Extractable Oxygenated Organics at Historic Crude Oil Release Sites

Oral Presentation

Prepared by R. Mohler1, S. Anh2, K. O’Reilly2, A. Tiwary2, D. Zemo3, R. Magaw4, N. Sihota4
1 - Chevron ETC, 100 Chevron Way, 50-1271, Richmond, CA, 94801, United States
2 - Exponent, 15375 SE 30th Place, Suite 250, Bellevue, WA, 98007, United States
3 - Zemo&Associates, 986 Wander Way, Incline Village, NV, 89451, United States
4 - Chevron ETC, 6001 Bollinger Canyon Rd, San Ramon, CA, 94583, United States


Contact Information: rmohler@chevron.com; 510-242-4939


ABSTRACT

Over the last 5-10 years there have been research projects funded to elucidate the composition of the extractable oxygenated organics that are measured as total petroleum hydrocarbon diesel range (TPHd) in samples of groundwater from historic fuel release sites. These results have shown that the majority of the oxygenated compounds detected downgradient from the source are acids/esters followed by alcohols, ketones, aldehydes, and phenols, and are assumed to be metabolites of hydrocarbon biodegradation. We have recently expanded our research project to the analysis of solvent extractable oxygenated organics at historic crude oil release sites. The advanced analytical instruments, comprehensive two-dimensional gas chromatography with time of flight mass spectrometry (GCxGC-TOFMS) and Orbitrap ESI-MS, were used to study the oxygenated compounds quantified as TPHd and dissolved organic carbon (DOC). Our GCxGC-TOFMS results for the crude oil sites are consistent with what was observed at fuel release sites. The Orbitrap results indicate that the dichloromethane extraction process can extract oxygenated organics up to C60s. There is a bimodal distribution of compounds with one hump peaking at around C20 and the other peaking at greater than C30s. Samples with higher TPHd tend to have more of the heavier compounds. It was determined that the composition of oxygenated compounds is increasingly similar to DOC with distance from the source and is of a much different composition than oxygenated organics found in the original oil. The GCxGC-TOFMS and Orbitrap methods and results will be presented.