Toward an assessment of copper bioavailability in treated wood

IRG/WP 10-20445

J S Schilling, J J Inda

Many modern wood preservative systems rely on copper (Cu). Some oxalate-producing fungi detoxify Cu by immobilizing it in crystals, and this may decrease its physiological availability (bioavailability). Cu bioavailability may also decrease during wood treatment. Cu retention in wood, however, is typically measured as a weight-to-volume concentration without an estimate of its bioavailability and without assessment of its relative contribution to preservative efficacy. We have begun assessing bioavailability of Cu in treated wood, using oxalate to pretreat wood and exposing wood to colonization by a fungus moderately-tolerant of Cu. In our first efforts, we treated Cu-impregnated wood with gradients of sodium oxalate and exposed rinsed wood in soil-block microcosms to Serpula himantioides. Cu ethanolamine (C-EA)-treated wood effectively prevents decay by S. himantioides, but toxicity can be overcome above a threshold level of oxalate pretreatment. In agar microcosms, C-EA wood stimulates oxalate production by S. himantioides, but the concentration of induced oxalate remains below the threshold determined in the soil-block trial and decay is low. We are working to improve the sensitivity of this biologically-relevant assay, but wish to share the idea with treaters and others with applied aspirations so that any emerging approach might better serve the wood protection community.


Keywords: copper tolerance, oxalate, ethanolamine, metals

Conference: 10-05-09/13 Biarritz, France


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