Effect of delayed drying time on copper distribution in the annual rings of ACQ-treated southern yellow pine research stakes

The copper in the new second-generation wood preservative systems for exterior residential applications in North America has been reported to require longer periods to fix in wood and to be more susceptible to leaching compared to the copper in wood treated with chromated copper arsenate. Treating small research stakes with a second-generation copper-rich system followed immediately by drying might lead to uneven copper distribution within annual rings, which could affect outdoor exposure efficacy and the amount of copper leached. Small ground-contact stakes were treated with 1 percent alkaline copper quat (ACQ-C), bagged for various periods to inhibit drying, then air-dried. The ratios of the copper retention in the earlywood vs. latewood (E/L) at the end and center of the stake were then determined. The E/L copper retention ratios continuously decreased in the stake center as the inhibited drying period increased from 0 to 8 days. In the stake end, the E/L end retention ratios decreased from 0 to 1 day of inhibited drying, but no further significant decrease was obtained as the bagging time increased from 1 to 8 days.

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