Assessment of laser induced breakdown spectroscopy (LIBS) for classification of preservative in CCA-treated lumber

In many parts of the world, efforts are being made to recycle chromated copper arsenate (CCA)-treated materials. While positive steps have been taken to identify CCA-treated lumber in the waste stream, little has been done to find a fast and accurate means to ascertain the level of preservative that exists in the lumber. The ability of the laser induced breakdown spectroscopy (LIBS) technique to determine the level of residual CCA preservative in reclaimed decking was assessed in this experimental pilot study. Control specimens at treatment levels of 0, 2.5, 3.7, 8.5, and 11.8 kg of CCA preservative per m3 of material (kg/m3) were analyzed to create a series of regression-fitted calibration lines. The most appropriate regression analysis with data reduction procedures were determined and subsequently used to comparatively predict the level of residual preservative relative to reclaimed decking lumber. Three different deck boards were investigated varying in age from 10, 18, and 25 years, and the remaining amount of preservative in the reclaimed specimens was verified using x-ray fluorescence. The current study revealed that LIBS possesses the potential to measure a threshold value of preservative, so that a reclaimed piece of lumber could be classified for an appropriate application that corresponds to its level of preservative retention. A more in-depth study is warranted to more fully evaluate the LIBS technique with greater certainty.