Enhanced Hydrocarbon Fingerprinting Methods Part I

By October 19, 2017 March 25th, 2019 No Comments
This blog post is a summary of the webinar presented by Dr. Kesavalu M. Bagawandoss of Test America entitled, Enhanced Hydrocarbon Fingerprinting Methods Part I.
Hydrocarbon fingerprinting is a forensic geochemistry technique that is used to evaluate various factors associated with the release of petroleum and petroleum products. Factors that can be determined using hydrocarbon fingerprinting include: what type of petroleum product has been released to the environment, how much degradation has the petroleum product undergone since its release, when the product was released, and ultimately where the release likely occurred.
Various methods are available to conduct hydrocarbon fingerprinting. This blog post will focus on the semi-volatile portion of fingerprinting.
The methods for semi-volatile analysis include:
  • GC/FID (gas chromatography/flame ionization detection);
  • GC/MS/SIM (gas chromatography/mass spectrometry/selected ion monitoring);
  • SW-846 8015 Modified;
  • ASTM D7363;
  • ASTM D5739;
  • SW 846 8270D Modified;
  • SINTED 2002;
  • Preparation Methods; and
  • Cleanup Methods.
All approaches to characterization are done in a tiered approach by starting at the simple analysis and ending at the most complicated. Analytical tiers are as follows:
  • Tier I – GC/FID: #4 Fuel Oil, #5 Fuel Oil, #6 Fuel Oil, Creosote Oil, Diesel #2 unweathered, Diesel #2 25% weathered, Diesel #2 50%, Diesel #2 75%, Gasoline unweathered, Gasoline 25% weathered, Gasoline 50% weathered, Gasoline 75% weathered, Jet Fuel A, Jet Propellant-4 (JP4), JP5, JP8, Kerosene unweathered, Kerosene 25% weathered, Kerosene 50% weathered, Kerosene 75% weathered, Mineral Oil, Mineral Spirits, Motor Oil, Hydraulic Oil, Transformer Oil, Crude Oils from various sources.
  • Tier II – GC/MS SIM
  • Tier III – CSIA (Carbon Stable Isotope Analysis)
  • Fuels comparison
  • TPH’s C8-C40 plus Pristane & Phytane
  • TPH’s C8-C44 plus Pristane & Phytane
  • ASTM D7900 Light Ends (Piano)(n-C2 – n-C10+) for light volatile compounds. If performed carefully even methane (n-C1) can be detected.
  • ASTM D7169 Simulated Distillation (n-C8 – n-C100)
Factors that affect hydrocarbon fingerprinting include:
  • Crude Oil Genesis – The temperature and pressure regime the crude oil formed under affect the “fingerprint” of the crude oil.
  • Petroleum Refining – The refining process creates multiple products (e.g. gasoline, diesel, jet fuel, etc) that each have their own unique “fingerprint”.
  • Weathering/Degradation – The weathering and degradation of petroleum and petroleum products creates substances with a different “fingerprint” than the original product.
  • Mixing With The Environment – Varying environmental factors and substances within the environment can interact with a petroleum product creating a substance with a different “fingerprint” than the original product.
All of these factors, in addition to other naturally occurring sources, affect the “fingerprint” of a product and need to be accounted for when analyzing.
Various techniques are used to analyze the data after the instrumentation process. Fingerprint comparison is used to compare the traces of the product to known product traces. Diagnostic ratios can be compared between the source and the spill or location where the sample was collected. Models and statistics can be used to extrapolate known data into the future (e.g. at the current rate, how long until product X is completely degraded into product Z). Mapping of the product plume can help visualize the situation within the subsurface.
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