PIXE analysis of copper, chromium and arsenic distributions in CCA-treated timber

PIXE is used for the elemental analysis of CCA treated timber samples, because of the simplicity of sample preparation, in-situ measurement of metal distribution, high sensitivity and the large number of samples which can be measured in a short time (typically less than 15 min per sample). The concentrations of Cr, Cu and As in the thin sections of treated poles from a vineyard were measured at 2 cm intervals from the centre of the pole. PIXE analysis indicated that in the case of fresh CCA treated timber the concentrations of Cu, Cr and As varied little with depth. In aged timber, the concentrations increased from the centre of the pole to the surface, indicating horizontal migration of these elements. The increase was greater for aged poles than for freshly treated poles, indicating surface migration of the CCA chemical with weathering. This was supported by data obtained in leaching experiments that indicated elevated concentrations of these metals in the extractants. (author)