Leaching of CCA from lumber exposed to natural rain aboveground

This paper presents results of a 1-year study that continuously monitored chromated copper arsenate (CCA) leaching from aboveground, naturally exposed 38-mm by 137.4-mm (2-in. by 6-in.) dimensional lumber samples. Three wood species, southern yellow pine (Pinus spp.), jack pine (Pinus banksiana Lamb.), and black spruce (Picea mariana (Mill.) B.S.P.) treated with two preservative concentrations, with and without commercial water-repellent and post-fixation washing treatments, were evaluated for their effects on leaching rates. Component leaching ranged from 7.3 to 20.5 ug/cm2 for chromium (Cr), 25.8 to 138 ug/cm2 for arsenic (As), and 19.1 to 78.6 ug/cm2 for copper (Cu) after 351 days of exposure. Black spruce treated with 1 percent CCA-C exhibited the highest percent loss of elements (1.6% Cr, 3.9% As, and 5.2% Cu), whereas southern yellow pine treated with 3 percent CCA-C and a water repellent displayed the lowest percent loss (0.1%Cr, 0.4%As, 0.6%Cu). In all cases, the water repellent treatment significantly reduced component leaching, whereas the pre-washing treatment produced inconsistent results.

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