VAPOR-PHASE STERILIZATION OF SOIL WITH ETHYLENE OXIDE

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Abstract
Most soils may be sterilized by vapor-phase treatment with ethylene oxide. The procedure consists of evacuating samples in a desiccator to 15 mm. pressure, treating with 0.8 to 1 atmosphere of ethylene oxide for 6-24 hrs., followed by air washing 3 times with filtered air. Sterility tests are made on all soils prior to use. In contrast to steam sterilization, this method does not alter the soil physically and gives no increase in soluble salts. However, pH is increased. Ethylene oxide is adsorbed by soil in amts. depending upon the time of exposure, texture or clay content, kind of clay, moisture content and organic content. About 50% or more of the adsorbed vapor is readily hydrolyzed to ethylene glycol even in soil treated air-dry. Being water-soluble, the glycol serves as readily available energy for microorganisms, which tends to limit appln. of the method. Evidence is presented of its usefulness in expts. where sterile, but otherwise physically and chemically unaltered, soil is required.