Comparison of methods for evaluating ground-contact copper preservative depletion

Abstract

Depletion of the biocide(s) used to treat wood has a major influence on service life and environmental concerns. However, little is known about the extent of depletion from the specific leaching method employed. Wood treated with two types of copper-based preservatives were leached using three different methods: field stakes (American Wood Protection Association (AWPA) method E7), laboratory soil exposure (AWPA method E20), or laboratory water immersion (AWPA method E11). Average losses tended to be greater from the field stakes than the small method E20 laboratory stakes, but this trend was difficult to substantiate because of the high variability with both methods. Little consistent relationship was observed between time of exposure and copper depletion in the field stakes, making it difficult to correlate the laboratory method with a specific duration of field exposure. Percentage of copper losses detected using AWPA method E11 appeared to be lower, and less variable, than those for either of the soil-contact leaching methods. The results of this study indicate that AWPA method E20 produces a range of leaching values more similar to field exposure than does AWPA method E11. All of these methods are intended to amplify and accelerate leaching, and therefore percentage depletion from commercial-size material would be substantially lower.

Citation

Lebow, Stan; Halverson, Steven. 2008. Comparison of methods for evaluating ground-contact copper preservative depletion. Proceedings, 104th annual meeting of the american wood protection association. 2008 May 18-20;Portland, OR. Birmingham, AL: American Wood Protection Association: Birmingham, AL: 55-60.