Cu2+ and Fe2+ mediated photodegradation studies of soil-incorporated chlorpyrifos
2016
Rafique, Nazia | Tariq, Saadia R. | Ahad, Karam | Taj, Touqeer
The influences of Cu²⁺ and Fe²⁺ on the photodegradation of soil-incorporated chlorpyrifos were investigated in the present study. The soil samples spiked with chlorpyrifos and selected metal ions were irradiated with UV light for different intervals of time and analyzed by HPLC. The unsterile and sterile control soil samples amended with pesticides and selected metals were incubated in the dark at 25 °C for the same time intervals. The results of the study evidenced that photodegradation of chlorpyrifos followed the first-order kinetics. The dissipation t₀.₅ of chlorpyrifos was found to decrease from 41 to 20 days under UV irradiation. The rate of chlorpyrifos photodegradation was increased in the presence of both metals, i.e., Cu²⁺ and Fe²⁺. Thus, initially observed t₀.₅ of 19.8 days was decreased to 4.39 days in the case of Cu⁺² and 19.25 days for Fe⁺². Copper was found to increase the rate of photodegradation by 4.5 orders of magnitude while the microbial degradation of chlorpyrifos was increased only twofold. The microbial degradation of chlorpyrifos was only negligibly affected by Fe²⁺ amendment. The studied trace metals also affected the abiotic degradation of the pesticide in the order Cu²⁺ > Fe²⁺.
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