ADSORPTION, DESORPTION, SOIL MOBILITY, AQUEOUS PERSISTENCE AND OCTANOL-WATER PARTITIONING COEFFICIENTS OF TERBUFOS, TERBUFOS SULFOXIDE AND TERBUFOS SULFONE

Terbufos, terbufos sulfoxide and terbufos sulfone (5 .mu.g/ml) were incubated in natural, sterilized natural and distilled water, with initial pH values of 8.8, 8.8 and 6.0, respectively, at 20.degree. C. First-order disappearance was observed. Rates in natural and sterilized water were similar, indicating that chemical degradation predominated. Terbufos disappeared rapidly (t1/2 [half-time] .simeq. 3 days) in all systems. Terbufos sulfoxide and terbufos sulfone were more persistent in the natural (t1/2 = 18-40 days) and distilled water (t1/2 = 280-350 days). Adsorption data for the 3 compounds in 4 soil-water systems showed the decreasing order of adsorption to be terbufos .mchgt. terbufos sulfoxide .simeq. sulfone. Desorption from soils fortified at 5 .mu.g/g with water was examined for 4 successive 18-h cycles. Terbufos sulfoxide and terbufos sulfone were totally desorbed; terbufos was too unstable to study. The mobility of the compound in soil eluted with water was in the order terbufos sulfoxide .simeq. terbufos sulfone .mchgt. terbufos, in agreement with adsorption-desorption results. The octanol-water partitioning coefficients for terbufos, terbufos sulfoxide and terbufos sulfone at 23.degree. C were 3:30 .times. 104, 164 and 302, respectively.