Pyrolysis-GC/FID Test for Biogenic Interference in Contaminated Soil

Abstract

“Biogenic interference” is that portion of natural organic matter in soil that cannot be distinguished from petroleum in a standard test for contamination. Biogenic interference is normally a small fraction of total natural organic matter. In organic soils, however, biogenic interference alone can exceed “petroleum” limits set by regulatory agencies. A test using a pyrolysis-gas chromatograph/flame ionization detector (GC/FID) was developed to quantify biogenic interference in soil samples from northern Alaska. The samples had no known history of contamination, so all measured “petroleum” was derived from biogenic interference. The pyrolysis test was found to predict biogenic interference in soil samples more accurately than any combination of standard soil tests, including C:N ratio, pH, percent organic carbon, extractable carbon, humic acids, fulvic acids, low molecular weight acids, hydrophobic neutrals, and hydrophilic neutrals. Analysis of samples contaminated in the laboratory confirmed that the pyrolysis test could quantify biogenic interference in soils recently contaminated by petroleum.