RELEASE OF FENAMIPHOS, ATRAZINE, AND ALACHLOR INTO FLOWING WATER FROMGRANULES AND SPRAY DEPOSITS OF CONVENTIONAL AND CONTROLLED-RELEASE FORMULATIONS

The release into water of active ingredients from spray deposits or gr anules of fenamiphos, atrazine, and alachlor was measured for commerci al and experimental controlled-release formulations. Granules or spray mixtures of the pesticides were mixed with coarse sand and dried if n ecessary, and the mixture was placed in 5 mm x 35 mm stainless steel c ylinders through which distilled water was then pumped for 24 h. Pesti cide concentrations in the eluate were determined by HPLC analysis. Th e conventional formulations (emulsifiable concentrates, granulars, and dispersible granules) gave total release in 5-24 h and in some cases appeared to release particles into contacting water. Controlled-releas e starch-encapsulated formulations gave between 5% and 94% release in 24 h. Clay/alginate and clay/alginate/linseed oil formulations gave 0. 3-100% release in 24 h, depending mainly on the aqueous solubility and lipophilicity of the pesticide. This simple technique provides compar ative insights into the amounts and rates of release of pesticide acti ve ingredients (and/or other chemicals such as oxidative degradates) w hen these formulations are contacted by flowing water. Initial results indicate that formulation can affect the potential of these pesticide s to be water pollutants under severe rainfall conditions.