Distribution of polycyclic aromatic hydrocarbons (PAHs) from legacy spills at an Alaskan Arctic site underlain by permafrost

Widespread polycyclic aromatic hydrocarbon (PAH) contamination resulting from petroleum spills at military and industrial sites along the Arctic Ocean Coast is a major issue in the Alaskan Arctic. Polycyclic aromatic hydrocarbons (PAHs) consist of one or more fused aromatic rings and comprise a major portion of petroleum products like fuels. PAHs are commonly found in a variety of geomedia and are considered environmentally persistent, toxic, and carcinogenic. In the present study, the subsurface distribution of PAHs was investigated at a former U.S. Department of the Navy site in northern Alaska using laser-induced fluorescence coupled with ultraviolet optical screening tool (LIF-UVOST). The former Naval Arctic Research Laboratory (NARL) study site has historical presence just outside the city of Utqiagvik, Alaska (formerly Barrow) and has a long history of petroleum spills since the early 1950s primarily at the Airstrip and Powerhouse sites. To determine the extent of PAH accumulation in the subsurface a total of 143 vertical soil profiles were characterized using LIF-UVOST during September 2015 (87 at the Airstrip site and 56 at the Powerhouse site). We also compared the intensities of different wavelengths (350 versus 500 nm) to estimate spill source and we found a substantial accumulation of PAHs in the surface and subsurface at both sites and vertical distribution of PAHs was primarily heterogeneous, varying as a function of probing locations and soil depth. Both sites were found to have no correlation between depth of the maximum fluorescence signal and depth of the probing refusal depth (top of permafrost). Using LIF-UVOST for the direct chemical sensing of PAHs proved to be a useful tool and revealed unique signature PAH fluorescence responses when comparing 350 and 500 nm intensities between the Airstrip and Powerhouse sites, likely attributable to the original source of the spill. Results from this project can be directly used for other potential studies, including planning remediation strategies and investigating local bodies of water for PAH transport.