Estimating Preservative Release From Treated wood Exposed to Precipitation<sup>1</sup>
Keywords:Leaching, methods, moisture content, precipitation, treated wood
AbstractAccelerated leaching methods are needed to better estimate emissions from treated wood used above ground or above water. In this study, we evaluated leaching methods using continuous immersion, dip immersion, and simulated rainfall approaches. Copper and/or boron emissions were measured for specimens treated with either chromated copper arsenate Type C (CCA-C) or a borax-copper (BC) preservative. The results of these leaching tests were compared with the extent of wetting and drying within the specimens and with the published reports of leaching and MC under natural exposures. Release per unit surface area was generally greatest with the simulated rainfall or constant immersion methods, but the relationship between the methods was dependent on the leaching characteristics of the specific preservative formulation. The lowest emissions were found for small specimens exposed to dip immersions. Comparison of the simulated rainfall results to published values indicates that the rainfall method and dip immersion scenarios underestimate copper release from wood exposed outdoors, and that the methods evaluated do not adequately simulate the wetting and drying conditions encountered in natural exposures. Further research is needed to better characterize the wetting and drying of in-service treated wood and to adapt test methods to more closely simulate these conditions.
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