| Abstrakt: |
The sorption of 1,1,1-trichloroethane on wheat, barley and oats during fumigation and its subsequent loss during airing has been studied after treatment with 1,1,1-trichloroethane alone or in a mixture with bromomethane. The extent of sorption of bromomethane and the amount of inorganic bromide formed from reaction of bromomethane with constituents of the grain samples were not affected by the presence of 1,1,1-trichloroethane. The sorption of 1,1,1-trichloroethane on cereal grains and the amount of inorganic bromide formed increased with commodity moisture content. Bromide formation also increased with temperature and varied both with the cereal and with different varieties of wheat tested. At low dosage levels, residues of 1,1,1-trichloroethane were proportional to concentration times; time (CT product) but at the highest dosage used residues were disproportionately higher than expected, owing to vapour concentration approaching saturation pressure. The rate of loss of 1,1,1-trichloroethane from wheat, barley and oats under controlled conditions was found to be more dependent on the storage time than on the residue remaining or the original level of treatment. For wheat, initial sorption of 1,1,1-trichloroethane varied with variety and to a lesser extent also varied between different samples of a single variety tested. However, the rate of airing appeared to be similar for all samples of wheat tested. Results are also described showing the effects on airing rates induced in wheat in which the moisture content was also changing. These results suggest that, in wheat in which moisture content increases during storage, the residue at a specific time after treatment would not be particularly dependent on the interim conditions while in wheat of falling moisture content, residues would very much depend on the conditions prevailing. A knowledge of these effects should help to refine attempts to extrapolate results of laboratory studies to commercial scale treatments. [ABSTRACT FROM AUTHOR] |
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