Distribution and composition of polycyclic aromatic hydrocarbons within experimental microcosms treated with creosote-impregnated Douglas fir pilings

Temporal changes in the concentration and relative composition of 15 priority polycyclic aromatic hydrocarbons (PAHs) in water, sediment, and polyvinylchloride (PVC) strips were assessed to evaluate the fate of creosote leached from impregnated wood pilings in aquatic environments. The study consisted of single microcosms containing one of 0.5, 1, 2, 3, 4, or 6 creosote-impregnated pilings and two microcosms containing untreated pilings. Quantitative analyses of PAHs were performed using highperformance liquid chromatography equipped with a fluorescence detector. For each treatment, total PAHs (Sigma PAH) in water increased rapidly up to 7 d posttreatment yielding a clear dose-dependant concentration gradient ranging from 7.3 (0.5 pilings) to 97.2 mu g/L (6 pilings). Total PAHs declined exponentially after 7 d and was reduced close to background concentrations (0.8-6.7 mu g/L) by the end of the study (84 d). No increase in Sigma PAH was observed in sediments at any treatment, nor was there any relationship between sediment PAHs and distance from each piling cluster. However, a slight increase in PAHs was observed on PVC liner strips that exhibited a concentration gradient similar to that in water. The PVC-bound Sigma PAH ranged from 0.3 to 2.4 mu g/cm(2) and 0.2 to 2.2 mu g/cm(2) at 31 and 58 d posttreatment, respectively. Based on these data, we estimated a rate loss of creosote from the pilings of approximately 50 mu g/cm(2)/d (273 mg/piling/d). The low concentration of PAHs on the PVC, along with the absence of accumulation of PAHs in sediments, suggests that creosote was lost primarily from water via degradative pathways such as photolysis and microbial decomposition and adsorption onto PVC. The rapid loss of creosote from water in conjunction with the slow rate of leaching from the pilings suggests that risks associated with the use of creosote-impregnated pilings in aquatic environments may be minimal.