An approach to uncertainty estimation in determining polycyclic aromatic hydrocarbons in fuel-contaminated soils

An estimation of uncertainty contribution in the entire set of the analytical data of polycyclic aromatic hydrocarbons (PAHs) in soil during a full year is presented. The analyses were performed as part of a project devoted to the assessment of the natural attenuation of selected PAHs in agricultural soil contaminated by a fuel spill. In particular, we investigated the effect of natural attenuation on the PAH dissipation rate in plots of two types of scenarios in agricultural soils. One of them was previously affected by an accidental fuel spill 10 years ago, and the other one was non-affected. The major components for estimating uncertainty contributions have been evaluated based on intermediate precision from different levels of PAH mass fraction, sample locations, and long term data set. An analysis of variance (ANOVA) test was applied to the mass fractions of clean or blank soil sub-samples versus contaminated soil sub-samples for grouping comparable data. Variables of influence in this study were site, month, and lysimeter of sampling (referring to a stainless steel box, with side lengths of 50 cm). Study sites or the spatial arrangement of lysimeter showed a clear effect in sub-sample results with the lowest mass fraction levels for heavier PAH, while monthly sampling was the variable of most significant influence for the more strongly contaminated sub-sample results.

Finally, the results of the PAH mass fractions in contaminated soil sub-samples indicated a monthly variation for which lighter, volatile PAHs rapidly decreased while the less volatile did not change.