Development of Respirometry as a Method for Evaluating Wood Preservatives

Use of the respirometer was studied in an effort to adapt this instrument to the evaluation of threshold or toxic limit values of wood preservatives. Most of the tests used southern pine sapwood 3/4 inch cubes. After impregnation with a series of retention levels of creosote, pentachlorophenol, or CCA type C preservative, they were placed in conventional soil-block cultures or malt-agar feeder strip cultures of Lentinus lepideus M-534, Lenzites trabea M-617, or Poria monticola M-698, respectively, for 2 to 4 weeks. They were then evaluated in the respirometer for amount of respiration,and the threshold calculated. Other wood species and 2.5 cc. sticks of southern pine were also used. The intersection of a regression line for retention versus oxygen consumption in microliters per hour with the 2.5 microliters per hour line gave the threshold values. For pentachlorophenol a value of 0.158 lb./cu.ft. was found for blocks on a soil culture for 4 weeks, but 0.169 lb./cu.ft. if on malt-agar for 4 weeks. For creosote, values were about the same from soil or malt-agar cultures, namely 6.6 versus 4-5 lbs./cu.ft. by weight loss methods. The smaller blocks gave threshold values about 12 percent higher for pentachlorophenol. Threshold of pentachlorophenol in eastern white pine was 38 percent lower than in sugar pine. Respirometry proved to be faster but more sensitive in detection and evaluation of decay than conventional weight loss methods.

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