Magnitude and variability of biogenic interference in cold regions soils

In organic soils commonly found in cold regions, many compounds with simila r characteristics are found in petroleum contamination and natural or ganic material (NOM). These similarities make it difficult to distinguish betwee n natural compounds and true contamination using standard test methods. "Bi ogenic interference" is the term used to describe the NOM quantified as "pe troleum" during a standard test for soil contamination. The inability to di fferentiate between biogenic interference and soil contamination is of conc ern because it can cause cleanup standards to be set at lower limits than t he actual contamination warrants. This paper presents the results from over 200 uncontaminated soil samples that were analyzed to determine the magnit ude and variability of biogenic interference in soils from cold regions. St udies were conducted to evaluate the correlation between fundamental physic al/chemical properties of soil and extractable NOM levels. Samples were als o collected and analyzed to evaluate spatial (vertical and horizontal) vari ations in background extractable NOM at one site. A final set of samples wa s analyzed to determine the range of background extractable NOM levels at u ncontaminated sites throughout Alaska. The results show that uncontaminated soil from across Alaska can contain several hundred to several thousand mg /kg of extractable naturally occurring diesel and residual range organics. A high degree of variability was observed in the amount of extractable NOM at different sites across Alaska and within a single site.