We hypothesized that X-ray micro-CT would be able to visualize: (a) the distribution of copper in CA-treated southern pine; and (b) microstructural changes in ACQ-treated southern pine exposed to natural weathering. Small blocks were removed from southern pine samples treated with CA and also southern pine treated with ACQ and MCA. Small blocks were also removed from ACQ-treated boards (flat and profiled) exposed to natural weathering for 12 months. Untreated blocks acted as controls. The microstructure of blocks including distribution of copper deposits were visualized using X-ray micro-CT. Copper in untreated CA blocks was concentrated in the walls of longitudinal parenchyma and ray parenchyma cells adjacent to resin canals, but it was also present in epithelial cells around longitudinal and radial resin canals, and around and within resin plugs in resin canals. Copper in the ACQ treated block was distributed similarly, but copper in the MCA-treated block was predominantly in the lumens of those parenchyma cells. Copper in weathered ACQ-treated samples was primarily associated with resinous epithelial cells and plugs, and less copper was present in parenchyma cells and in tracheids near the weathered surface. We conclude that the distribution of copper deposits in CA-treated wood is associated with the 3D parenchyma network. The distribution of copper deposits in ACQ-treated wood changes during weathering and is associated to a greater extent with resinous areas in the parenchyma network.

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