Environmental Assessments
- Oil Spills Forensics
- Assessing the Origin of Gas Seepages
- Evaluation of Petroleum Biodegradation and Soil Pollution
Origin of an oil spills can be constrained or pinpointed by sophisticated chemical analyses that distinguish between various oils. In this context, PGGRC offers reliable solutions to determine the origin of oil spills. Our analytical services include:
- Whole oil gas chromatography: Oils in the immediate area of the spill can be used to identify the origin of the spill. This approach requires collection and analysis of all nearby potential source oils for the spill. When a positive correlation of spilled oil and facility oil occurs, then the origin of the spill has been determined. If the spilled oil has undergone weathering, water washing, and/or biodegradation, then biomarker analysis and/or other techniques may be required to identify the spill source.
- Biomarkers: Since different potential sources of a spill may involve oils derived from different basins, biomarker distributions can be used to either rule out or rule in potential sources of a spill. More specifically, these compounds can be used to determine if oil in a contaminated area actually represents more than one spill.
- Polycyclic aromatic hydrocarbons (PAH): These are another group of compounds present in oil that are especially useful in identifying the source(s) of a spill. PAHs are resistant to biodegradation typically encountered in spill situations. They provide a useful tool for correlating a biodegraded oil to a its non-degraded equivalent, and hence can be use to identify the source(s) of a petroleum release.
- Stable carbon isotope measurements: Different oils commonly have different carbon isotopic compositions. Therefore, carbon isotopic analyses of petroleum samples from a contaminated area can be used to constrain the source(s) of the contaminant in a contaminated area.
Natural gas can have two primary origins in sediments: methane produced by methanogenic bacteria (biogenic gas) and hydrocarbon gas produced by thermal alteration of sedimentary organic matter (thermogenic gas). Unlike thermogenic gas, biogenic gas is always very dry and does not contain significant ethane, propane or higher-molecular-weight homologues (i.e., wet gases). In addition, biogenic methane contains isotopically lighter carbon (i.e., is more depleted in 13C) compared to thermogenic methane. Geochemical analyses conducted at PGGRC can readily reveal if a gas seep represents thermogenic or biogenic gas and thereby help reduce exploration risks in poorly explored regions.
Microorganisms biodegrade different classes of compounds in petroleum at different rates. As a result, the progressive biodegradation of an oil spill can be monitored by periodic analyses of various compounds in the oil-contaminated soil. The early stages of oil biodegradation (loss of paraffins and isoprenoids) can be readily detectable by gas chromatographic (GC) analysis. However, in heavily degraded samples, GC analysis alone cannot distinguish subtle differences in biodegradation due to interference of the unresolved complex mixture (UCM or hump) that dominates the GC traces. Fortunately, in heavily degraded oils, one can use gas chromatography-mass spectrometry (GC-MS) to quantify the concentrations of biomarkers with differing resistances to biodegradation, allowing the extent of biodegradation to be monitored over time. In an oil, the quantity of a biomarker that is resistant to biodegradation increases as the oil is biodegraded, because such a compound is "concentrated" in the oil by the loss from the oil of the other less-resistant compounds. Therefore, by comparing the concentration of such a resistant compound in a spill with the concentration of the same compound in the original oil, one can estimate how much of the oil has been degraded.