Comparison of fixation rates of earlywood, latewood, sapwood, and heartwood of CCA-treated Douglas-fir, southern pine, and eastern larch

Fixation rates of chromated copper arsenate (CCA) type C wood preservative in earlywood, latewood (cut from sapwood), whole sapwood, and whole heartwood of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii), southern pine (Pinus spp.), and eastern larch (Larix laricina (Du Roi) K. Koch) were compared at 21?C and 60?C and high humidity. Fixation was monitored by following the reduction of hexavalent chromium (CrVI) in solution expressed from wood by centrifuge. CrVI fixation rate was always significantly faster in more dense latewood than in earlywood in each species. CCA also fixed more rapidly in heartwood than in sapwood in all species. Generally, CrVI fixation rate in the sapwood of Douglas-fir was slightly slower than in southern pine and larch. These results illustrate the large variability in fixation rates between and within species.

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