Decomposition of Phenoxyalkyl Carboxylic Acids
1962
Burger, K. | MacRae, I. C. | Alexander, M.
The persistence of phenoxyalkyl carboxylic acids in soil was measured by a bioassay technique using alfalfa seedlings. Acetic, alpha-propionic and alpha- and gammabutyric acid derivatives were toxic when applied to soil planted to alfalfa whereas the beta-propionic acid derivatives showed no inhibition of the test plant. All 3,4-dichloro- and 2,4,5-trichlorophenoxyalkyl carboxylic acids exhibited prolonged persistence in soil. The duration of phytotoxicity in soil receiving 4-chloro-, 2,4-dichloro- and 2-methyl-4-chlorophenoxyalkyl carboxylic acids was governed by the type and linkage of the aliphatic side chain. A Flavobacterium sp. active in the degradation of phenoxybutyric acids was isolated. The bacterium metabolized only phenoxybutyric acids having no meta chlorine on the aromatic ring. In the decomposition, the organic chlorine was liberated and the aromatic ring cleaved. The results demonstrate that specific structural characteristics of these herbicide molecules govern persistence of the compounds in soil.
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