EFFECT OF TREATMENT POSTFIXATION PRACTICES ON COPPER MIGRATION FROM ALKALINE-COPPER-TREATED DOUGLAS-FIR LUMBER

Abstract

The potential for preservative migration from treated wood exposed in or above aquatic environments has become a major concern in some parts of the United States. Best management practices (BMP) were designed to decrease the potential environmental footprint of treated wood, but there are few studies assessing the efficacy of these processes. The effects of applying various post-treatment BMP heating processes on loss of copper from copper azole Type B (CA) and alkaline copper quaternary compound Type B (ACQ)-treated Douglas fir were evaluated using a simulated overhead rainfall apparatus. This study examined the initial phases of wetting, which previous studies have shown to pose the highest risk to aquatic life. Immersion of CA-treated wood in hot water or a dilute ammonia solution was associated with lower levels of copper in rainfall runoff than steaming or kiln-drying, whereas steaming was associated
higher copper levels. Similar trials with ACQ revealed that various heating treatments produced results that were similar to those found with air-drying. The results suggest that there might be opportunities for decreasing copper losses from CA-treated wood through further refinements in post-treatment BMPs. They also indicate that post-treatment heating processes that do not dry the wood still produce products that experience copper losses similar to those found with air-dried material.