Contribution of Dissolved Organic Carbon in Mobilizing and Releasing High Molecular Weight Polycyclic Aromatic Hydrocarbons From Carbonaceous Material-Amended Soil

Introduction: Migration and mobilization of recalcitrant organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) in contaminated sites may endanger groundwater resources if considerable amounts of these compounds are mobilized and leached from solid phase into aqueous phase. The aim of the present study was to investigate the influence of biochar in two forms i.e. crushed and pulverized on immobilization and leaching behavior of high molecular weight (HMW) PAHs from contaminated soil into water as well as evaluation of contribution of dissolved organic carbon (DOC) in mobilization and release of HMW PAHs in crushed and pulverized biochar-amended soil, which was addressed for the first time in this study. Materials and Methods: Column leaching test was used to evaluate the leaching behavior of selected HMW PAHs from soil. Concentrations of PAHs in column leachates were determined using a GC/MS. Results: Findings showed strong sorption of the studied HMW PAHs to solid phase in both unamended and amended columns. Dibenz[a,h]anthracenewas not mobilized by water flow in any of the examined treatments and showed the greatest affinity to solid matrix. Mobility and leaching of most HMW PAHs were enhanced in the presence of crushed biochar. Direct correlation between detected concentrations of HMW PAHs in column percolates and DOC was found in biochar-amended soil. Conclusions: Biochar can be used as a promising cost-effective alternative to activated carbon in immobilization of PAHs in contaminated sites. However, contribution of DOC in mobilization of HMW PAHs from contaminated soils towards groundwater resources cannot be neglected.