Influence of exposure time, wood species and dimension on the remaining copper and chromium content in CC-treated wood after field and laboratory leaching tests

Most studies on preservative depletion from treated wood are performed with small samples on a laboratory scale. Although these studies provided repeatable and constant test parameters, the results have little applicability to real conditions. Therefore, a series of laboratory tests were carried out according to CEN/TS 15119 part 1 and part 2 by means of EN 252 and non-standard sized Scots pine sapwood as well as spruce stakes. The stakes were impregnated by vacuum pressure with chromium (Cr)-copper(Cu)-containing wood preservative. For comparison, a set of 18 stakes per test parameter was installed at a test site (in ground use), whereby, every 4 months, three stakes from each series were removed for analysis. Both the time depending losses of metal as well as the remaining element contents were determined for samples exposed under lab conditions, whereas distribution and remaining element contents were measured for samples exposed in the field. The obtained data were evaluated regarding factors influencing the metal leaching, such as exposure time, wood species, or dimension. The results showed that wood species had a significant effect on the Cu depletion, while it had less influence on the Cr loss. Cr and Cu distribution in the standard and non-standard sized pine sapwood significantly changed as compared to spruce. In addition, comparison of the laboratory and field test results indicated that metal depletion is greater in field exposure compared to both laboratory tests.