Adsorption, desorption, soil mobility, aqueous persistence and octanol-water partitioning coefficients of terbufos, terbufos sulfoxide and terbufos sulfone.

Terbufos, t.sulfoxide and t.sulfone (5 micrograms ml-1) were incubated in natural, sterilized natural and distilled water, with initial pH values of 8.8, 8.8 and 6.0, respectively, at 20 degrees C. First-order disappearance was observed for the three compounds. Rates in natural and sterilized water were similar indicating chemical degradation predominated. Terbufos disappeared rapidly (t1/2 congruent to 3 days) in all systems. T.sulfoxide and t.sulfone were more persistent in the natural (t1/2 = 18-40 days) and distilled water (t1/2 = 280-350 days). Adsorption data for the three compounds in four soil-water systems showed the decreasing order of adsorption to be terbufos much greater than t.sulfoxide congruent to t.sulfone. Desorption from soils fortified at 5 micrograms g-1 with water was examined for 4 successive 18-hr cycles. T.sulfoxide and t.sulfone were totally desorbed; terbufos was too unstable to study. The mobility of the compound in soil eluted with water was in the order, t.sulfoxide congruent to t.sulfone much greater than terbufos, in agreement with adsorption-desorption results. The octanol-water partitioning coefficients for terbufos, t.sulfoxide and t.sulfone, at 23 degrees C, were 3:30 x 10(4), 164, and 302, respectively.