Bioavailability and bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in historically contaminated soils after lab incubation with sewage sludge-derived biochars

The objective of this study was to estimate the effectiveness of application of sewage sludge-derived biochars for the immobilisation of freely dissolved (C-free) and bioaccessible (C-bioacc) polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. Soil SL-COK collected from the area of a coking plant and soil SL-BIT collected from the area of a plant producing bituminous materials were chosen for the study. The biochars were produced from. sewage sludge at temperatures of 500 degrees C (BC500) or 700 degrees C (BC700). The biochars were mixed with the soil at the dose of 5% and incubated for a period of 60 d. The content of PAHs was determined with the use of polyoxymethylene (POM) (C-free) or a solution of cyclodextrins and silicon rod elastomer (C-bioacc). Biochars reduced the content of C-free and C-bioacc PAHs in soils. A higher level of reduction was noted for C-free PAHs than for C-bioacc PAHs. Biochar produced at 700 degrees C was more effective in the reduction of Cfree and C-bioacc PAHs than biochar produced at 500 degrees C. It was found that in the soil in which the source of contamination were processes related with the production of bituminous materials (SL-BIT), the effect of reduction of C-free and C-bioacc was greater than in soil SL-COK where the source of PAHs were coking processes. It also needs to be emphasised that soil SL-BIT, for which better reduction of PAHs was noted, was also characterised by a lower affinity towards those compounds than soil SL-COK. (C) 2016 Elsevier Ltd. All rights reserved.