Persistence of terbufos and its metabolites in soil and maize

Degradation of 14C terbufos was studied under greenhouse conditions. A mixture of 14C labelled compound (2.48 x 104 Bq of O-ethyl-1- 14C) und unlabelled compound (0.09 g of the granule formulation Counter 10 G) was applied to pots containing 750 g of sandy loam clay Ultisol soil with 4.9% organic matter and a cation exchange capacity of 7.6. Two treatments were established, one where maize (cultivar Cristiani) was grown and the other without plants. The soil and plants were extracted at 0, 4, 8, 16, 32 and 64 days and analyzed by a liquid scintillation counter, gas chromatography-flame photometric detector (GC-FPD) and autoradiography. The total 14C compounds extracted on day 64 were 31 ± 5.6% of the radioactivity applied in the treatments with plants and 46.1 ± 1.1% without plants. From the autoradiography results it can be concluded that all times the compounds identified by this technique were terbufos, terbufos sulphoxide and terbufos sulphone. These results will be compared with those to be obtained by GC-FPD and another extraction method. Plant extracts are currently being analysed. (author). 6 refs, 4 figs