Migration of contaminants in permafrost active layer; new insights from on-going studies at the former Naval Arctic Research Laboratory, Barrow, Alaska

Accidental releases of fuel on to soils underlain by continuous permafrost are challenging to delineate because of the difficulty in predicting the migration of hydrocarbons through the active layer, that is the shallow sub-surface zone that melts during the summer. Permafrost is an effective aquitard but movement of water through the active zone is constrained by low hydraulic gradients, inhomogeneous aquifers and the morphology of the underlying permafrost surface. Consequently, the movement of contaminants within the active layer is complex. Further, microbial breakdown and oxidation of contaminants is retarded by the low temperatures, so that contaminates remain at elevated concentrations for much longer that at more temperate latitudes. The Naval Arctic Research Laboratory (NARL) was operational from 1947 until 1980 occupying a 350-acre site north of the city of Barrow. Most of the original structures at NARL are still intact and have been put to other uses. However, complete utilization of the facility is limited by soil contamination dating back to its former use. Most of the contamination relates to fuel spills but metals, PCBs and chlorinated solvents are also present at some locations above action levels. Characterization and remediation efforts have been ongoing since the Navy left NARL and are expected to continue for another decade or more. As one of the most intensely studied sites in the Arctic, NARL is an ideal location to investigate long-term migration within the active zone.