Creosote Contamination in Sediments of the Grey Owl Marina in Prince Albert National Park, Saskatchewan, Canada

Abstract

The rate at which creosote-treated pilings release polycyclic aromatic hydrocarbons (PAHs) into the environment should diminish with structure age and weathering, and so, it may be assumed that PAH concentrations in the vicinity of old structures (>30 years) may approach background levels. However, this may not be true in cold environments where PAH release and degradation rates are slow and where pilings continue to experience significant physical damage. Moreover, PAHs will remain high in the vicinity of pilings if current and wave action is insufficient to disperse and dilute PAHs over a wider area and/or where PAHs do not become diluted and buried by uncontaminated sediments. This is demonstrated in our investigation of the sediments of the Grey Owl Marina, located in Prince Albert National Park, in central Saskatchewan, Canada. The marina, constructed in the early 1960s, consists of six piers and is protected from strong wave action by a breakwater. PAH concentrations were high in sediments collected under the piers and inside the boat slips, exceeding probable effect levels for several compounds. Various lines of physical and chemical evidence pointed to creosote as being the primary PAH source with a mixture of relatively undegraded and weathered PAHs being present. PAH concentrations decreased rapidly 2 m and further away from the pilings as a result of dilution with increasing dispersal over a broadening area. There was evidence of benthic community impairment, with total abundances negatively correlated with PAH concentrations. According to the Methods for Ranking Contaminated Aquatic Sites on Canadian Federal Properties, areas with the highest hazard scores were under the piers and inside the boat slips, while areas with the lowest hazard scores were >10 m from the pilings. Therefore, remedial actions based on piling and contaminated sediment removal may need to be conducted over only a small area, i.e., within 2 m of the pilings.