Determining PCB desorption behaviour on sediments with SFE and investigating the dependency of selective fractions on sediment characteristics

A method for studying PCB desorption behaviour from sediments using supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE) is presented. Four sediments were investigated and extracted with supercritical carbon dioxide employing increasingly harsher extraction conditions ranging from 40 degrees C and 12MPa to 100 degrees C and 36.5 MPa. To ensure quantitative extractions, the remaining SFE residues were also extracted with PLE. Resulting profiles identified at least three different PCB fractions within the four sediments. Furthermore, a distinct fraction was obtained with extraction for 2 h at 40 degrees C and 36.5 MPa. This fraction has previously been found to correlate well with bioavailable fractions. The dependency of this fraction on sediment total organic carbon (TOC) was investigated, both for sediments examined in this study as well as for previously reported values using the same extraction conditions. It was found that TOC does not correlate to selective SFE, which indicates that the use of TOC to predict bioavailability is questionable.