X-ray microanalysis using thin sections of preservative-treated wood: Relationship of wood anatomical features to the distribution of copper

The objective of this study was to understand the micro-distribution of a copper-based preservative in wood in connection with anatomical morphology and to consider the fixation of copper in wood. Bulk specimens and semi-ultra thin sections (0.5 μm) obtained from Japanese cedar (Cryptomeria japonica) were treated with a CuAz preservative solution. After fixation of the solution in wood components, SEM-EDXA (Scanning Electron Microscope equipped with an Energy Dispersive X-ray Analyzer) was used to investigate the micro-distribution of copper. The use of semi-ultra thin sections improved characteristic X-ray spatial resolution and made it possible to analyze the micro-distribution of copper. In both earlywood and latewood of the sapwood, copper was more abundant in the compound middle lamella than in the secondary wall and concentrated in the tori. Copper was most concentrated as crystalline deposits in longitudinal parecnhyma cells. Semi-quantitative analysis revealed the copper amount to increase in this order: secondary wall in tracheids < middle lamellae < membrane of half-bordered pits < tori in tracheid pits < deposits in longitudinal parenchyma cells. These different concentrations may indicate significant interactions between the amine-copper complex in CuAz and chemical constituents of wood.

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