Fixation and leaching of red maple (Acer rubrum L.) treated with CCA-C

Fixation and leaching of chromated copper arsenate (CCA) Type C wood preservative in red maple (Acer rubrum L.) boards were investigated using the expressate method to follow chromium fixation and a shower test to determine leaching properties during fixation. These studies were supplemented with studies on 19-mm blocks that were assessed for chromium fixation by expressing and for CCA component leaching after fixation by the AWPA E11-87 leaching procedure. Chromium fixation in red maple is substantially faster at both 21?C and 60?C than in a typical softwood, red pine. In small block samples, 5 to 10 hours were sufficient to achieve complete chromium reduction at 21?C, compared to about 500 hours required for red pine. At 60?C, red maple was fixed in about 1.5 hours, compared to about 15 hours for red pine. The rate of fixation was not affected by extraction of acetone-soluble extractives or by the method of treating (vacuum vs. pressure), but in some cases, it appeared that larger samples required more time to fix than small block samples. The percentage of arsenic leached from red maple, both the boards exposed to a shower test and the blocks exposed to the AWPA test, was much higher than that normally seen in red pine and other commercial softwoods. The chromium and copper losses were in the normal range observed in softwoods. This high arsenic leaching from red maple wherein the chromium has been fully fixed is cause for concern for products used in environmentally sensitive locations.

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