Persistence of quinalphos and occurrence of its primary metabolite in soils

Quinalphos is used widely in India for the control of pests in cotton, groundnut, and rice. A study was conducted to examine the formation of the quinalphos metabolite, 2-hydroxyquinoxaline, during degradation of the parent compound in soils under aerobic conditions. A red sandy loam sandy clay soil and a black clay soil were used, which were both sterile and nonsterile. Results showed that the dissipation rate of quinalphos followed first-order kinetics. The rate constant and half-life for quinalphos disappearance in black soil and in red sandy loam sandy clay soil were 0.0533 and 0.0462/d, and 13 and 15 d, respectively. Quinalphos persisted to the same extent in the soils with and without pre-exposure, but the recovery of 2-hydroxyquinoxaline was higher from soils with repeated quinalphos applications.