Creosote movement from treated wood immersed in fresh water

Creosote has a long history of successful use as a wood preservative, but polycyclic aromatic hydrocarbons in this preservative have raised environmental concerns, particularly when creosote-treated wood is used in aquatic environments. A number of models have been developed to predict the risk of creosote use in aquatic environments, but one limitation of these models is a lack of data on the initial rates of creosote migration from treated wood. In this study, the effect of flow rates on creosote migration from freshly treated wood immersed in fresh water were examined. Seven of 16 polyaromatic hydrocarbons listed as hazardous pollutants were de­ tectable with the analytical protocol developed. Creosote component levels declined from values in the tens of μg/cm2 day to undetect­ able levels within 7 days, with the exception of phenanthrene, indicating that creosote migration decreased sharply after initial expo­ sure. These data provide the experimental foundation for the development of mathematical models to predict emissions from creosote-treated wood into the aquatic environment. Creosote has been widely used to protect railroad ties, util­ ity poles, bridge timbers, and piling against fungal, insect, and marine borer attack since its introduction in the 1830s. Creosote is a distillate of coal tar, a byproduct of the carbonization of coal. Creosote is thus a complex mixture of hydrocarbon compounds, including nearly 80 percent by weight of polycyclic aromatic hydrocarbons (PAHs) (Environment Canada 1992). PAHs are nonionic, similarly structured organic compounds character­ ized by low water solubilities and high partition coefficients with organic matter (Swartz et al. 1995, Vilholth 1999). Public concern has been raised because some PAHs con­ tained in creosote have shown acute and chronic toxicity to ma­ rine animals (Ozretich et al. 2000, Brooks 2000). However, no increased cancer risk was found for workers handling and us­ ing creosote on a daily basis (Alscher and Lohnert 1985). Al­ though creosote has relatively low toxicity, continuous release of PAHs into the environment might potentially create prob­ lems. While hydrocarbon pollution associated with transporta­ tion has been broadly investigated, there are relatively few data on the migration of PAHs into surrounding environments from creosote-treated wood exposed over or adjacent to surface wa­ ter. Brooks (1996) pointed out that the release of creosote com­ ponents from treated wood created the potential for biological impacts. He also detected elevated PAH levels in the sediments 1.8 to 3.0 m downstream from creosote-treated bridges. Brooks (1996) reported PAH contamination and significant biological impacts near newly installed piling. Swartz et al. (1995) devel­ oped a model to predict PAH toxicity in sediments, and Ozretich et al. (2000) tested PAH models at creosote-contaminated sites. Mathematical models associated with PAH re­ leases from immersed creosote-treated wood were also devel­ oped to assess the environmental risks associated with use of these materials (Brooks 1996). Water flow rate, however, could not be included in the models, despite its potential impor­ tance, because of a lack of data. The absence of such data makes it difficult to build accurate predictive models for as­ sessing environmental impacts of PAH contamination. The authors are, respectively, Research Scientist, Korea Forest Re­ search Institute, Seoul, Korea; Professor and Associate Professor (john. [email protected]), Dept. of Wood Science and En­ gineering, Oregon State Univ., Corvallis, OR, and Research Wood Scientist, USDA Forest Products Lab., Madison, WI. This paper was received for publication in July 2004. Article No. 9916. ✳Forest Products Society Member. ©Forest Products Society 2005. Forest Prod. J. 55(12):42-46.