EFFECTS ON PAH CONCENTRATION FOLLOWING CLOSED SYSTEM INCUBATION AND SUBSEQUENT PERTURBATION OF AGED PAH CONTAMINATED SOIL

Polycyclic aromatic hydrocarbons (PAHs) are a concern as widespread persistent organic contaminants in soil due to carcinogenic, mutagenic, and toxic reproductive effects in humans and other organisms. A wide variety of chemical, biological, thermal and soil washing techniques exist and are widely implemented as remediation strategies. However, the hydrophobic nature of PAHs contributes to their tendency to sorb to soil organic matter, often necessitating the need for surfactants to improve solubility and efficiency of remediation. These practices can lead to secondary pollution and residual PAHs may remain in the impacted area. In the present study, soil samples from a 2010 dilbit spill site were collected revealing the presence of 7 priority PAH substances in all samples 5 years post-remediation, highlighting the persistence of these compounds in natural environments. Upon field collection in 2015, PAH concentrations were determined using HPLC (High Performance Liquid Chromatography). Portions of the collected samples were then used to construct soil-water microcosms for long-term (>7 year) evaluation under anaerobic, closed conditions. Results show PAH concentrations have decreased significantly over time but have remained in measurable concentrations in the soil fraction while only naphthalene and fluorene were found partitioned into the water fraction. Over the summer of 2023, 3 microcosms were opened, analyzed for PAH concentration, and then chemically perturbed to simulate a sudden shift in environment (ex. introduction of oxygen, change in pH, physical disturbance). Post-perturbation PAH concentration monitoring is ongoing. Initial results indicate a greater decrease in PAH presence following disturbance. While in-situ research is needed, these laboratory results indicate long-term natural attenuation processes of residual PAH compounds should be given consideration in future monitoring plans, especially in anticipation of changing environmental conditions.