| This thesis examines chromated copper arsenate (CCA) leaching from treated wood exposed to natural rain and laboratory leaching. Lumber specimens were subjected to 685 mm of precipitation during 351 days of exposure. Leaching rates (mug/cm2) of chromium, arsenic, and copper were similar for the three species evaluated (jack pine, black spruce, and southern yellow pine). Application of a water repellent reduced leaching losses by approximately 50%, while a post-fixation pressure washing treatment had mixed effects. Regression analysis revealed that 30% of the variation in chromium and arsenic leaching, and 44% of the variation in copper leaching was explained by sample treatments and climatic variables. A comparison of laboratory leaching methods reveals the need for harmonization of current standards. The American Wood Preservers Association Standard (AWPA E11-97) displayed the highest leaching, followed by the European Standard (EN-84), an independent test, and a method developed by industry. Percent loss from the laboratory leaching standards greatly overestimated leaching from 351 days of above ground exposure. Less than 5 hours of AWPA E11-97 leaching, and less than 21 hours of EN-84 leaching were required to leach the equivalent amount as 351 days of above ground exposure. |
