The use of sequential supercritical fluid extraction for bioavailability investigations of PAH in soil

The influence of soil organic matter (SOM) content on the bioavailability o f polycyclic aromatic hydrocarbons (PAH) was investigated by performing bio degradation experiments and comparing these data to results from a sequenti al supercritical fluid extraction (SSFE) method. Two model soils with diffe rent SOM (soil 1:2.1%, soil 2:8%) were contaminated using anthracene oil co ntaining fluoranthene as the major high molecular weight PAH. After spiking , soils were stored for 135 days in order to assess the influence of aging on the biodegradation and extractability of fluoranthene. Moreover, experim ents were also performed on an industrial soil, which was already contamina ted several decades ago. For non-aged samples, advanced degradation was ach ieved in soil 2 (higher in SOM). However, for aged samples, degradation was lower in soil 2 indicating that sequestration was more pronounced in the h igh organic matter soil. To evaluate the retention/release behavior of PAH in soil as an important: factor influencing their bioavailability, a SSFE m ethod was developed comprising eight subsequent extraction steps. For aged spiked soils extraction data indicate a reduced recovery when high in SOM. These findings are in line with the respective microbial degradation result s. However, for non-aged samples no difference in extraction recovery could be observed for both, low and high organic matter soils. Finally, for indu strially contaminated soil an inverse relationship between the molecular we ight of PAH and their extraction recovery was observed.