Adsorption, desorption, soil mobility and aqueous persistence of fensulfothion and its sulfide and sulfone metabolites

Abstract

Soil/water interactions with the insecticide fensulfothion and its sulfide and sulfone metabolites are described. Adsorption to, and desorption from four soils were studied. There was a general inverse relationship between water solubilities of the three chemicals and their adsorption K values. Order of adsorption was f.sulfide>f.sulfone>fensulfothion. Adsorption K values correlated significantly with soil organic content. Desorption of fensulfothion and the sulfone were similar whereas the less soluble sulfide desorbed to a lesser extent. To facilitate comparison of desorption tendencies of the three compounds a desorption index was developed. Mobilities through the soils were directly related to the water solubilities of the three chemicals. Mobilities in decreasing order were ‐fensulfothion>f.sulfone>f.sulfide. Persistence of fensulfothion was similar in both sterile and non‐sterile natural water ‐ about 50% remaining at the end of the 16 wk experiment. Under reducing conditions fensulfothion disappeared from water in 8–12 wk with almost complete conversion to the sulfide.

Key words:

• fensulfothion
• adsorption
• desorption
• persistence