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Influence of preservative treatment on durability of ACA-treated white spruce poles Kim, Won Jang


In 1977, sixty-two white spruce pole sections were installed at the Western Forest Products Laboratory's Westham Island test field site. They had been commercially pressure-impregnated with ammoniacal copper arsenate (ACA) or pentachlorophenol (PCP). Twenty-four of the ACA-treated spruce poles were studied to determine the influence of preservative penetration, retention, and nitrogen level on decay resistance of spruce poles after seven years of field testing. Such information was considered of great value in establishing treated spruce as viable pole material in Canada. Studies using a 0.5% solution of chrome azurol S indicated that for the ACA-treated spruce poles after seven years in test, average preservative penetration of 1.14 in. (2.90 cm) was generally greater than that required by Canadian standards. However, analysis using energy-dispersive X-ray spectrometry showed that the mean retention of 0.50 lb./ft.³ (8.06 kg/m³) was less than the level of 0.6 lb./ft.³ (9.6 kg/m³) for ACA, required by the CSA standard. It was also found that copper was present in greater quantity than arsenic, in spite of their equal presence in the original ACA treating solution. In microbiological studies, a total of seventy-one fungal isolates belonging to seventeen genera and four taxa were identified to genus, with fifteen of these identified as to species. Unlike the untreated control poles, true wood-decaying Basidiomycetes were not found associated with the ACA-treated spruce poles. Analysis employing an Orion ammonia-specific electrode coupled to an Orion Microprocessor ionalyser 901 revealed that nitrogen content due to ACA treatment was significantly increased in the treated zone and also beyond the penetration limit of preservative. A linear relationship existed between nitrogen content and chemical retention in the first analytical zone. Variation in moisture content above the fiber saturation point produced marked changes in electrical resistance as detected by Shigometer measurements. The practical application of the Shigometer for detection of internal decay is limited by such inconsistencies.

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