Photodegradation of α-cypermethrin in soil in the presence of trace metals (Cu2+, Cd2+, Fe2+ and Zn2+)

Abstract

The influence of trace metals (Cu²⁺, Zn²⁺, Cd²⁺ and Fe²⁺) on the photodegradation of α-cypermethrin (α-CYM) in agricultural soil was studied. The soil samples were spiked with α-cypermethrin with/without the presence of metal ions, irradiated under a UV irradiation chamber for a regular period of time and analyzed by using HPLC. The dark control sterile and unsterile soil samples spiked with α-cypermethrin and selected trace metals were incubated for the same interval of time at 25 °C. The results obtained indicated that α-cypermethrin photodegradation followed biphasic kinetics. α-cypermethrin photodegradation half-lives (t_1/2) were increased to 0.71 and. 4.5 hours from 0.64 hours respectively in the presence of elevated Zn²⁺ and Cu²⁺ concentrations. Fe²⁺ and Cd²⁺ increased the photodegradation reaction kinetics from −1.078 h⁻¹ to −1.175 h⁻¹ and −1.397 h⁻¹ and varied the t_1/2 from 0.64 ± 1.41 to 0.59 ± 2.07 and 0.49 ± 2.01 in the soil. Microbes also affected the degradation of α-cypermethrin in metal contaminated soil. The degradation rate was inhibited in unsterile soil and was found to be in the following order: Cd²⁺< Zn²⁺< Cu²⁺< Fe²⁺. The degradation/persistence of α-cypermethrin was affected linearly with the increasing soil metal concentrations.