Penetration of naphthalene, n-hexadecane, and 2,4-dinitrotoluene into southern yellow pine under conditions modeling spills and floods

Abstract

This paper investigates the penetration of three common contaminants into building grade southern yellow pine wood samples under the conditions experienced during chemical spills. Contaminants (n-hexadecane, naphthalene, and 2,4-dinitrotoluene) were applied in their 14C-labeled forms to 5-to 9-cm-long pieces of southern yellow pine at ambient conditions. The impact of the following parameters on diffusivity was investigated: contaminant volatility and solubility in water, penetration direction compared to wood grain structure, and water saturation of wood under conditions characteristic of catastrophic floods. Water saturation (having a dramatic effect on diffusion rates) was studied under three conditions: wood pieces with ambient water concentration, those “post-soaked” with water after contamination, and those pre-soaked with water before contamination. Contaminant diffusivities in the ambient samples increased with increased contaminant volatility. For more water-soluble compounds. naphthalene and 2,4-dinitrotoluene, the diffusion rate was greater in post-soaked samples with diffusivities approaching 10-9 m2/s, characteristic for their diffusion in bulk liquids. By contrast, n-hexadecane diffusion was hindered significantly in post-soaked samples. For all three contaminants, longitudinal and tangential penetration rates were similar, indicating that the rate-limiting step may be contaminant evaporation inside the wood tracheids or contaminant dissolution in water (diffusion being controlled by strong contaminant sorption in wood). Experiments with pre-soaked samples and those conducted under external capillary pressure showed different trends from non-pressurized post-soaked samples, indicating a possible switch in the rate-limiting steps for contaminant diffusion under these conditions.

Citation

Popova, I.E.; Beklemishev, M.K.; Frihart, C.R.; Seames, W.S.; Sundstrom, T.J.; Kozliak, E.I. 2006. Penetration of naphthalene, n-hexadecane, and 2,4-dinitrotoluene into southern yellow pine under conditions modeling spills and floods. Forest products journal. Vol. 56, no. 6 (June 2006): pages 68-75.