Penetration of n-Hexadecane and Water into Wood under Conditions Simulating Catastrophic Floods

To simulate fuel oil spills occurring during catastrophic floods, short-term absorption of two chemicals, n-hexadecane (representative of semivolatile organic compounds in fuel oil) and water, into southern yellow pine was gravimetrically monitored as a function of time at ambient conditions. Different scenarios were run on the basis of (1) the order of contamination (n-hexadecane followed by water or vice versa) and (2) whether the wood lateral sides were covered with epoxy. The experiments were designed to evaluate fast initial sorption, allowing separate estimation of the end-grain (i.e., total longitudinal) and lateral (i.e., surface longitudinal) liquid penetration. Presaturation of wood with water did not significantly impede the subsequent penetration of n-hexadecane, whereas the presaturation of wood with n-hexadecane led to a significant decrease of the subsequent water uptake. This difference in penetration on the basis of the order of application was explained by the differences in the polarities of the two penetrating liquids and their impacts on the interactions with the wood matrix. Calculated apparent diffusivities for end-grain and lateral penetration were similar at ca. 3 x 10(-7) m(2)/s, indicating that filling of easily accessible near-surface voids does not have a substantial impact on the overall penetration of contaminants into wood. The n-hexadecane distribution profiles based on penetration into wood blocks (obtained by means of gas chromatography) showed that water and n-hexadecane appear to use different (although overlapping) penetration paths owing to the differences in their physical properties.