Azinphosmethyl

The Koc of azinphosmethyl in five European soils was measured in the range of 487 to 4,644(1). Azinphosmethyl also had Koc values of 1990 (75.0% clay, 3.29% organic carbon), 783 (22.6% clay, 2.39% organic carbon), 570 (17.0% clay, 3.32% organic carbon), 630 (20.3% clay, 1.36% organic carbon) and 1700 (6.0% clay, 4.43% organic carbon) in five European soils(2). Using data from the 1993 UK database, Koc values for azinphosmethyl were 298 to 3406(3). According to a classification scheme(4), this Koc data suggests that azinphosmethyl is expected to have moderate to slight mobility in soil. Measurable residues were found in sediment samples after application to the surface of littoral enclosure mesocosms; the sediment and water were identified as the most important sorptive compartments(5). The compound is not likely to leach to groundwater except in areas of high recharge such as karst(6).

No azinphosmethyl was detected (detection limit was 0.4 ppm) below the top 2 inch soil layer in an apple orchard where 4 applications of azinphosmethyl totaled 3 pounds/acre(1). Azinphosmethyl was not transported deeply into the soil of an irrigated potato field. Traces were found at a soil depth of 12-30 cm but none was found below 30 cm(2). In a thin layer chromatography (TLC) experiment, azinphosmethyl was found to have a low mobility in Hagerstown soil (silt clay loam, 1.4% organic content)(3). In another study, soil TLC experiments were conducted using azinphosmethyl and 14 different soils(4); the average Rf value for azinphosmethyl was 0.17. Field moisture capacity (FMC) and organic matter content of a soil were found to be a good predictor of mobility. Increased FMC decreased the soil mobility in the TLC experiments(4). No azinphosmethyl was detected in a soil column effluent after 64 days and batch studies indicate that sorption was not reversible(5). An experimental Koc of 189 (Kom of 110) has been reported(6) but the isotherm was not linear. The pesticide root zone model (PRZM - designed to predict pesticide movement in unsaturated soils within and below the root zone in agricultural systems) was applied to study pesticide movement in a 25 ha managed loblolly pine (Pinus taeda L.) forest near Comer, GA(7). The model indicates that azinphosmethyl has little potential to leach to ground water, given a Kd value of 10, Koc of 1,000, and a soil half-life of 40 days(7). A mean Kd of 8.94 in nine soils was also reported(8).