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Environmental Forensic Analysis Using Enhanced Petroleum Hydrocarbon Testing | Eurofins TestAmerica Laboratories

Enhanced Petroleum Hydrocarbon Testing

Environmental Forensic Testing

Crude oil and oil products contain a complex mixture of hydrocarbons as well as minor amounts of sulfur, oxygen, nitrogen, nickel and vanadium.  Due to variations in crude oil and refining processes, environmental samples have unique chemical fingerprints that can provide the basis for identifying and distinguishing the sources of released oil or oil products.  The release of hydrocarbons into the environment can require extensive environmental cleanup activities as well as an assessment of the potential damages to terrestrial, aquatic and/or marine natural resources. In certain situations, the spatial and temporal extent of damages may need to be assessed using chemical fingerprinting.

Chemical Fingerprinting

Chemical fingerprinting allows for the comparison of unique diagnostic chemical features of potentially impacted environmental samples.  Data is used to assess potential liability as well as monitor short and long term environmental impacts.  Chemical fingerprinting can include the determination of petroleum hydrocarbons as petrogenic, pyrogenic and/or biogenic based on patterns.

Environmental forensic chemists use data generated from specialized environmental hydrocarbon testing methods such as those for Saturated Hydrocarbons (SHC), Polycyclic Aromatic Hydrocarbons (PAHs) and their alkylated homologs and/or Petroleum Biomarkers.  Saturated hydrocarbons and biomarkers are used together to track source signatures of petroleum in the environment.  Saturated hydrocarbons can identify the petrogenic source (distillates, residual petroleum or coal).  Biomarkers can be used to distinguish petroleum sources.

Saturated Hydrocarbons (SHCs)

SHCs are the simplest and most dominant class of hydrocarbons in crude oil.  They contain only single bonds between carbon atoms and each carbon atom is saturated with hydrogen.  Cycloalkanes are also SHCs since they are single bonded carbon atoms joined in a ring structure.

Pristane and phytane are the dominant saturated hydrocarbon biomarker isoprenoid components of crude oils.  The pristane/phytane (Pr/Ph) ratio is used as an indicator of the oil source. These correlations are based on the concept that the composition of biomarkers in spill samples does not differ from those of the source oils.  The ratio of the pristane to n-alkane C17 (Pr/n-C17) and phytane to n-alkane C18 (Ph/n-C18) are a rough indication of the relative state of biodegradation.  The SHC analysis provides for the distribution of alkanes from C8 to C40, as well as selected isoprenoids [pristane & phytane] & cyclohexanes.

Polycyclic Aromatic Hydrocarbon (PAH) & Alkylated Homologs (aPAH)

PAHs have two or more fused aromatic-ring compounds consisting solely of carbon and hydrogen molecules.  The PAHs most commonly encountered in the environment contain two to seven fused benzene rings.  PAHs in petroleum products range from one- to five-ring combinations.

The unsubstituted aromatic structures are referred to as the parent PAHs.  These PAHs can also have branched or alkyl group substitution on their ring structures that are referred to as Alkylated PAHs. The alkyl groups generally have one to four saturated carbon atoms, and thus can produce many different structural homologs for each aromatic hydrocarbon family. The most abundant aromatic hydrocarbon families have one to four carbon atom alkyl group substitutions denoted by C1-, C2-, C3-, and C4.  Parent PAHs in petroleum products are usually present in low concentration since crude oils contain primarily the alkyl PAHs.   In contrast, parent PAHs in coal tar can be found in high concentrations. Therefore, a full PAH signature including the alkylated homologs is required for an environmental forensic evaluation.

Biomarkers

Biomarkers are complex molecules derived from the formerly living organisms that are the basis of the crude oil. Biomarkers are unique in that they are weather resistant and show little or no change to the parent organic molecules. Due to the wide range of geologic conditions, these compounds retain most of their organic chemical structure from their original product, and are the source signatures of petroleum.  These compounds provide more information about the oil source than any other compounds.  In comparison to the other components of crude, they are often found in low concentrations. The chemical analysis of these compounds and diagnostic ratios are frequently used for oil release identification by environmental forensic chemists.   

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