Diffusion of wood preservatives is an important process in wood treatment ensuring long term stability of wood products. In order to assess the effectiveness of commercially used wood preservative treatment, the penetration and fate of a representative radiolabeled fungicide in softwood was studied. The longitudinal and transversal penetration of 14C-labeled tebuconazole (TAZ) in pine wood was investigated in addition to the changing rate of diffusion over time. Treatment time of 30 s and 180 s had similar profiles of TAZ distribution. The concentration of TAZ was highest within 3 mm from wood surface in transverse direction and 10 mm in longitudinal direction. Based on the obtained diffusion coefficients, the bulk of TAZ travelled together with the solvent and their diffusion was 10x faster for the first 30 s. The effective diffusion coefficient for TAZ increased with the penetration distance. Therefore, a small fraction of TAZ traveled much faster and penetrated deeper than the bulk. The fate of preservatives was studied by exposing the treated wood to diverse environmental conditions for 6 months. Significant losses (70 – 80 %) were observed for radiolabeled TAZ in the aged wood near the surface compared to controls even after the application of an exhaustive extraction method. Little or no biodegradation was observed based on the similarity of TAZ profiles with and without a treatment with sodium azide. In addition, liquid chromatography with high resolution mass spectrometry was used to study any potential degradation products; however the decrease in 14C carbon response suggested that vaporization plays a significant role in the loss of TAZ.

Diffusion and aging of wood preservatives in softwood under environmental exposure

249th National Meeting (2015)

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