Appendix A of this document and in our Demonstration Plan in section 5.4 "Sampling Plan" and
Appendix D "Sampling and Analysis Plan for Annette Island and Campion."
For semi-volatile TPH and FSH analyses, soil samples were extracted in n-pentane, passed
through an open silica column, and fractionated into aliphatic hydrocarbons (F1 fraction) and
aromatic hydrocarbons (F2 fraction) using open tubular silica gel chromatography techniques.
The resulting extracts are analyzed for TPH and FSH and, for selected samples, for PAHs.
3.6.1 Total Petroleum Hydrocarbons (TPH).
High-resolution gas chromatography using flame ionization detection (HRGC/FID) yields a
chromatogram (see Appendix A for a description of the HRGC/FID technique). These
chromatograms show relative amounts of petroleum compounds as they differentially elute from
a chromatographic column. Integrating the area under the curve and between two defined
retention times provides a measure of TPH. TPH data are generally provided as a single, numeric
concentration value, such as mg/kg or ppm; thus, much of the data contained in the
chromatogram is lost because a numeric TPH value gives no qualitative information about the
distribution of fractions. Nonetheless, when monitored over time, TPH data can show, in general,
if concentrations of petroleum products are decreasing. To rely mainly on TPH as a monitoring
tool, you must assume homogeneity of initial concentrations or have large concentration
changes.
3.6.2 GC Fingerprinting (Fuel Types and Weathering)
With experience, the same chromatograms used for obtaining TPH values can be compared to
typical curves of known products and provide information about types of petroleum products and
degree of weathering.
3.6.3 Fraction-specific hydrocarbons (FSH)
Fraction-specific hydrocarbons (FSH) are based on the concept that petroleum consists of a very
large number (~104) of individual compounds. The distribution of broad classes of these
compounds is reasonably representative of different types of petroleum products, such as diesel
or bunker C. A combination of distillation and blending of the distillates are used to obtain
petroleum products. Consequently, rather than being a set percentage of different compounds,
petroleum products are combinations of various distillation fractions that are blended together to
provide a product that meets performance guidelines. Chemically, various fractions of petroleum
compounds behave similarly and, hence, can be grouped together. Chemical similarities
influence both extraction from soil and also the potential toxicity of the compounds. The FSH
approach was developed based on these properties. Specific FSH values are obtained similarly to
TPH curves but, following extraction from soil and prior to GC analysis, the petroleum materials
are fractionated into aliphatic and aromatic components. When quantifying the chromatogram for
FSH, the ranges used to group compounds have been chosen based on correlations with potential
toxicity. The initial fractionation provides quantitative measures for specific fractions of the
petroleum material. Changes in FSH values can be compared through time. Because different
petroleum fractions have different transport, bioavailability, and toxicity characteristics, FSH
data can be more meaningful than TPH data. FSH values are obtained using the HRGC/FID
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