The bioavailability of perfluoroalkyl substances (PFASs) and polycyclic aromatic hydrocarbons (PAHs) in soil to Eisenia fetida and Cucurbita pepo

Abstract: Persistent organic pollutants (POPs) are organic chemicals of great concern because of their persistency, bioaccumulation and toxic effects both in the environment and to humans. Two groups of organic chemicals that are partly listed as POPs are perfluoroalkyl substances (PFASs) and polycyclic aromatic hydrocarbons (PAHs). PFASs are man-made organic chemicals that became of concern in recent decades due to their presence in wildlife and humans. PAHs are organic chemicals that are produced unintentionally as a result of incomplete combustion. The two main purposes of this master thesis were 1) to investigate the bioavailability of PFASs and PAHs in soil to earthworm (Eisenia fetida) and zucchini (Cucurbita pepo), and 2) to study the influence of PFASs on the availability of PAHs. Two different groups of soils (field-contaminated and spiked soils) were studied. The earthworm experiment was done in 7 weeks and the plant experiment in 12 weeks. Chemical analysis was done by liquid chromatography coupled to mass spectrometry (LC-MS\MS) and gas chromatography coupled to mass spectrometry (GC-MS\MS) for PFASs and PAHs, respectively. Bioaccumulation factors (BAFs) and biota-soil accumulation factors (BSAFs) were calculated for the uptake in E. fetida while bioconcentration factors (BCFs) were calculated for the uptake in C. pepo. The BAFs for PFASs were generally larger than BAFs for PAHs; therefore it can be said that PFASs are more bioaccumulative than PAHs. The BSAFs of PFASs in earthworms increased when the perfluorocarbon chain length increased, but the chain length had an inverse effect on BCF in zucchini, showing a decreased BCF when the chain length increased. The effect of the functional group of the PFASs on BSAF and BCF was studied, and no significant differences between the compounds with the same chain length but different functional groups could be observed. Moreover, BSAFs of PAHs had a slight tendency to increase with an increase in log KOW. The bioavailability of PAHs in two soils, one without PFASs and one with PFASs, was compared and it was shown that the PAH availability increased in the presence of PFASs.