Leaching Characteristics of Phenanthrene and Pyrene in Biochar-amended Contaminated Soil

Contamination of soil with persistent organic contaminants has been of great concern due to their long-term effects in the environment. Polycyclic aromatic hydrocarbons (PAHs) are a well-known group of organic contaminants characterized by their resistance to biodegradation and high hydrophobicity. Mobilization and migration of PAH compounds in hydrocarbon-contaminated site may endanger groundwater resources. The main objective of this study was to investigate the influence of pulverized biochar on immobilization and release characteristics of model PAHs. Column leaching test was used to simulate leaching of PAH compounds from contaminated solid phase towards aqueous phase. Results showed strong sorption of both studied PAHs i.e. phenanthrene and pyrene to soil particles, however, at the end of the experiment 5.32% and 0.99% of the initial solid phase content of, respectively, phenanthrene and pyrene released into water in unamended soil. Application of pulverized biochar could finally reduce mobilization and cumulative release of the above-mentioned PAH compounds significantly. Similar trend was also obtained for sum 16 US EPA PAHs. Variation of pH during the leaching process and its contribution to mobilization and release of selected PAH compounds, which has scarcely studied previously, were also addressed. Results indicated that pulverized biochar as a cost-effective alternative to other carbon-rich amendments e.g. activated carbon can be effectively employed for site remediation purposes to reduce mobilization of PAHs in soil.