Hydrolysis and soil sorption of insecticide pyraclofos

Abstract

The hydrolysis of the insecticide pyraclofos in buffered solutions at pH 5.0, 7.0 and 9.0, and its sorption on four soils of different physicochemical properties were investigated. The results showed that the degradation of pyraclofos in buffered solutions followed pseudo-first-order kinetics. At 40°C, the rate constants for the hydrolysis of pyraclofos at pH 5.0, 7.0 and 9.0 were 0.0214, 0.1293, and 2.1656 d⁻¹, respectively. Pyraclofos was relatively stable under both acidic and neutral conditions, while it was readily hydrolyzed under basic conditions. The sorption of pyraclofos on four soils was well described by the Freundlich equation. The sorption constant, K _f, increased with an increase in soil organic carbon content, suggesting that organic carbon content was an important factor affecting sorption. The K _oc values for Xiaoshan clay loam soil, Hangzhou I clay loam soil, Hangzhou II soil, and Fuyang silt loam soil were 30.4, 6.7, 5.3, and 7.1, respectively. These results suggest that the sorption of pyraclofos on the tested soils was relatively weak.

Keywords:

• Pyraclofos
• hydrolysis
• sorption
• organophosphorus insecticide

Acknowledgments

This work was financially supported by The Program for Changjiang Scholars and Innovative Research Teams in Chinese Universities (No. IRT 0653) and The Natural Science Foundation of Zhejiang Province, China (No. Z506070).

Notes

^aHalf-life was calculated as T_1/2 = (ln2)/ k _obsd.