Abstract:

To evaluate the environmental safety of the new molluscicide pyriclobenzuron, the hydrolysis characteristics of pyriclobenzuron at room temperature (25 ℃) and in buffer solutions with different pH values, as well as its degradation characteristics in two water-sediment systems, were studied under laboratory conditions according to national standards (GB/T 31270—2014). The hydrolysis half-life of pyriclobenzuron in buffer solutions with pH values of 6.58, 9.10 and 12.13 was greater than 180.00 d, belonging to difficultly degradable pesticides. In a buffer solution with a pH value of 4.15, the hydrolysis half-life of pyriclobenzuron was 13.86 d, which was less than 30.00 d, belonging to easily degradable pesticides. Besides, the degradation of pyriclobenzuron in the Shaoxing and Jiashan water-sediment systems followed a first-order kinetic equation. The aerobic degradation half-lives of pyriclobenzuron in aqueous phase were 7.53 and 7.79 d, respectively. Pyriclobenzuron gradually migrated from the aqueous phase to the sediment, and the detected concentration of pyriclobenzuron in the sediment remained relatively stable over a period of time. In summary, pyriclobenzuron was difficult to degrade in neutral and alkaline water environments under dark conditions, while it belonged to easily degradable pesticides in acidic water environments. Pyriclobenzuron belonged to easily degradable pesticides in two water-sediment systems at 25 ℃. In conclusion, it is expected to be used for the prevention and control of Pomacea canaliculate in actual rice paddy environments with less environment risk.

Key words: pyriclobenzuron, molluscicide, water-sediment system, hydrolysis