DEVELOPMENT OF PROCEDURES FOR IDENTIFYING PESTICIDE TOXICITY IN AMBIENT WATERS - CARBOFURAN, DIAZINON, CHLORPYRIFOS

The responses of carbofuran, diazinon, and chlorpyrifos to standard ac ute toxicity identification evaluation (TlE) procedures were character ized. The test species was Ceriodaphnia dubia. The TIE procedures incl uded solid-phase extraction, recovery in methanol eluates, hydrolysis under acid and base conditions, and retention in specific methanol/wat er fractions. In addition, the effect of the metabolic inhibitor, pipe ronyl butoxide, on the toxicity of each of the pesticides was determin ed. Diazinon degraded quickly under acid conditions, whereas carbofura n degraded under base conditions. In both cases, concentrations were r educed to nontoxic levels within 6 h. Conversely, acidic or basic cond itions were not effective in reducing the concentration of chlorpyrifo s over the same time period. Solid- phase extraction removed at: least 95% of diazinon and carbofuran from solution, but was less effective with chlorpyrifos. All three pesticides eluted separately in character istic methanol/water fractions. Piperonyl butoxide ameliorated the tox icity of diazinon and chlorpyrifos, but not carbofuran. Up to 1.5% met hanol did not interfere with the protective action of piperonyl butoxi de. Case studies in which these techniques were applied to ambient wat er samples are also described.