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The release of a pesticide active ingredient (AI) from granules into water and soil is a subject of interest because it can answer questions about product efficacy or pest control, persistence of the AI in the soil environment, degradation of the AI, and translocation of the AI from agricultural fields to bodies of water. Attempts have been made in lab settings to simulate field conditions in order to predict the extent and rate of elution of AI from granules into surrounding soil conditions, or to determine the rate at which the AI comes out of the granules. Although these techniques are helpful, they do not provide a quick and simple answer to whether or not the active ingredient comes out of the granules when a rain event is simulated. A simplified laboratory method for quantifying the released amount of the organophosphate terbufos into water from a granular carrier has been developed. The objective was to determine whether there was movement of the AI out of the granule when it was exposed to water. Water was added to the granules in a way that simulated a rain event, and the release of terbufos out of the granule was evaluated with both repeated elutions (open system) and single elution (closed system). The concentration of terbufos in the water was tested via liquid-liquid (LLS) and solid-phase extraction (SPE) methods. In a comparison of these two water extraction techniques, SPE proved to be more efficient than LLS and was chosen for testing samples. Three commercially available granular formulations were tested for the release of AI, and the results showed differences among the formulations. For both elution systems, repeated and single, a higher concentration of terbufos was found in water leached from granule A than from granules B and C. The difference may be attributed to the clay composition or the addition of co-formulants in the samples tested. Material reconciliation experiments were able to confirm the quantity of AI remaining in the granules after leaching.
release, extraction, leaching, reconciliation
Oil-Dri Corporation of America, Chicago, IL