Direct observation of the distribution of radiolabelled ethirimol in soil by resin impregnation and autoradiography

A procedure for examining the distribution of ethirimol in soil is described. Soil samples containing ethirimol are initially freeze-dried at −5 to −10°C, impregnated with Araldite resin and hardeners under vacuum and then maintained for 16 h at room temperature followed by 24 h at 100°C, to complete curing. The impregnated soils may then be sectioned and the radiolabelled pesticide located by autoradiography. The distribution of ethirimol within the soil was found to be unaffected by either freeze-drying or impregnation. The method enables the distribution to be determined on a small scale directly in undisturbed soil sections from both the laboratory and the field. It was used to investigate the effects of soil type on the movement of ethirimol. Structural and textural factors appear to have an important influence on the redistribution of this fungicide and may override the effects of adsorption.