Study on the hysteresis effect of pulse export of pesticides from paddy fields in the plain river network area
Currently there is a lacking of information on the export processes and the transport mechanism of pesticides shortly after application in paddy fields,so this paper presents an experimental study conducted in the Irrigation and Drainage Research Station of Jiangdu District of Yangzhou City in Jiangsu Province.The pulses of both field drainage and pesticides losses from paddy fields after application events were monitored with high frequency sampling.The pulse export processes of the pesticides which were normally used(chlorpyrifos,abamectin,tricyclazole and thifluzamide)were captured.The results indicated the peaks of concentration and load rate of the aforementioned pesticides occurred 5and 2.5h after application.The pulse export characteristics was obvious.The phase lag of pesticides and drainage was significantly influenced by anthropogenic factors and exhibited randomness to certain extent.For the more soluable fungicides(tricyclazole and thifluzamide),the hysteresis indices were 0.419 and 0.326,respectively.Their losses were much affected by the field hydrologic conditions,presenting an evident concentration and flow(c-Q)hysteresis phenomenon.Such phenomenon is related to the order of pesticide application in the paddy fields and the transport pathway of pesticides from fields to ditches.For the more volatile insecticide(chlorpyrifos),however,the losses were much affected by uncertain factors such as wind direction,no c-Q hysteresis phenomenon was observed with the hysteresis index of merely 0.083.The flushing indices of tricyclazole,thifluzamide and chlorpyrifos were equal to or close to 1,illustrating that the drainage pulse exhibited flushing effect to pesticides.Findings from this research may help understand the mechanism of pesticide pollutions in paddy environment and provide technical support for pesticide pollution control.
万方数据
维普
