Abstract
The model to predict concentration of pesticides in the atmosphere after application on the paddy field was investigated using the Gaussian plume equation as an atmospheric diffusion model. The model was on the assumption that the pesticide was constantly discharged from the emission source, the sprayed area was topographically flat, the wind direction and the wind speed were constant. The area source was combined by 50 m square of mesh, and a point source was located in the center of the mesh. The emission rate was derived from the observed concentration inside the sprayed area, and it was observed that the emission rate decreased with elapsed time and the emission rate had a positive correlation with vapor pressure. The emission rate was estimated by vapor pressure, a temperature and elapsed time after application, then an emission rate, a plume height and a meteorological and geographical conditions were input into the area source plume equation, a predicted concentration was calculated. As a result, the predicted concentration showed significant correlation with the observed concentration (p<0.01). The predicted concentrations generally ranged from l/10 to l0 times the observed concentrations. Therefore, this model is useful for predicting pesticide concentrations.
