| Abstract
| - In situ indicators of degradation are important tools in thedemonstration of natural attenuation. A literature surveyon the production history of phenoxy acids and degradationpathways has shown that metabolites of phenoxy acidherbicides also are impurities in the herbicide products,making the bare presence of these compounds useless asin situ indicators. These impurities can make up morethan 30% of the herbicides. Degradation of phenoxy acidswas demonstrated in microcosm experiments usinggroundwater and sediment contaminated with MCPP,dichlorprop, and related compounds such as otherphenoxypropionic acids and chlorophenols. Field observationsat two phenoxy acid-contaminated sites showed theoccurrence of several impurities including metabolites inthe groundwater. Neither the microcosm experiments northe field observations verified that metabolites wereactually produced or accumulated in situ. However, itwas demonstrated that the impurity/parent herbicide ratioscan be useful in situ indicators of degradation.
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