Leaching of preservative components from pine decking treated with CCA and copper azole, and interactions of leachates with soils

IRG/WP 01-50171

M J Kennedy, P A Collins

Radiata pine decking was treated with CCA and copper azole preservatives to Australian H3 retention using conventional and modified Bethel schedules, and air-dried. Treated decking boards and durable hardwood controls were subjected to leaching in weather-exposed decks, and matching 19mm cubes were leached in extended AWPA E11-97 lab tests. Deck runoff and E11 leachate water was analysed after rain events and E11 change points. After 10 months, decks had lost up to 700mg Cu, 175mg Cr, 600mg As, 750mg B, 10 mg tebuconazole or 18000 mg tannin per square meter of deck, but flux rates had not yet reached zero for any component. Leaching from E11-97 blocks was much faster and greater than from the decks. Extending the leach period from 14 days to 50 days increased the amount of leaching by up to 40%. Even after 50 days, flux rates were measurable for most components. Deck leachates were applied to three soils using the draft OECD soil leaching column procedure. After elution, the soil was segmented and analysed. Although boron was more mobile than others, components tended to be retained in the topmost (first contacted) layer.


Conference: 01-05-20/25 Nara, Japan

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