PERSISTENCE OF PESTICIDE-RESIDUES IN ORCHARD SOIL

The behaviour and disappearance of Diazinon and Prometryn from orchard soils were monitored in a typical orchard plot in Valencia (Spain). Soil samples were collected at two different depth ranges (0-5 cm, and 5-30 cm below the soil surface) at each of five sites within the plot. The samples were taken from several horizons in order to determine whether or not there was any leaching of the pesticide. Since soil heterogeneity can affect pesticide behaviour in terms of adsorption, transport and persistence, soil characterization is necessary; hence, tests for determining sand, silt and clay content were also carried out. A simple, rapid and effective method was used for extracting and enriching pesticides, based on the use of 47-mm disks with octyl bonded silica sorbent. The adsorbed pesticides were eluted with ethyl acetate prior to capillary gas chromatography.