PERSISTENCE OF TEMEPHOS AND ITS TRANSFORMATION PRODUCTS IN RICE CROP FIELD WATERS

The persistence of temephos and its degradation products (temephos sul foxide, temephos isomer, and temephos sulfoxide isomer) under real env ironmental conditions was studied. Other breakdown products identified were temephos oxon and temephos oxon isomer. Temephos was applied in the rice crop field of the Ebre Delta (Tarragona, Spain) during July a nd August 1994 by aircraft spraying ABATE 50E at a rate of 250 mL/Ha; the calculated concentration range in the rice crop field waters was b etween 41 and 125 mu g/L. The evolution of temephos and its transforma tion products was recorded during a period of 72 h with sampling inter vals of 5 and 10 h. The concentration of the compounds formed was meas ured inside and in the outlet of two rice crop field waters and varied between 0.01 and 2.27 mu g/L. Only a maximum of 5.5% of the applied t emephos was detected immediately following application. The analytical determinations were performed by using solid-phase extraction with C- 18 Empore extraction disks followed by liquid chromatography/thermospr ay/mass spectrometry (LC/TSP/MS) in the positive ion mode.