The adsorption–desorption processes of pymetrozine were investigated in three cultivated soils in China through a batch method. Pymetrozine was determined by high-performance liquid chromatography (HPLC). At a relatively low temperature, the adsorption of pymetrozine improved with increasing organic matter content, and the Freundlich model precisely illustrates the adsorption isotherms. The adsorption of pymetrozine was classified as physical, considering that the Gibbs free energy change values of this process in the three soils ranged from –21.195 kJ/mol to –23.956 kJ/mol. The ΔH value was –37.236 kJ/mol for soil A, –13.723 kJ/mol for soil B, and –9.154 kJ/mol for soil C, suggesting that the major interaction in the adsorption involved hydrogen bonds and that the adsorption of pymtrozine in the three soils was exothermic. Soil C was shown to have the highest hysteresis among the samples. The hysteresis was enhanced at high temperatures for soil B and soil C but reduced for soil A. Pymetrozine adsorption increased with decreasing temperature, suggesting that pymetrozine may infiltrate groundwater at high temperatures.

Crop protection pesticide spraying aims to greatly improve the utilization rate of pesticides. Controlling pesticides deposition requires a thorough understanding of the spatial behaviour of spray droplets.The Qinghai-Tibet Plateau, which is the headwaters of three largest water resources (Yangtze, Yellow and Lancang) in China, has exceptionally unique climatic characteristics. The goal is to reduce the amount of pesticides entering water resources. The wind tunnel experiment was used to validate the discrete phase method for tracking the trajectories. Cooperation between the smaller and larger droplets (greater than 150 μm) in the dense area around the nozzle can undoubtedly enhance the initial dispersion of droplet sizes. Droplet coalescence, which lowers the proportion of readily dispersed droplets, can greatly boost droplet deposition onto the target location.The crucial drift height is presented and clarified when droplets gradually disperse by identifying the descending length at which efficiency of mass transit starts towards decrease off quickly. The pesticide transport efficiency will not be enhanced by reducing the initial relative spread of droplets if the actual spray height surpasses the crucial drift height, and may even worsen drift loss. The temperature and relative humidity of the air have a greater influence on the evaporation losses of droplets smaller than 150 μm. In addition to providing information about pesticide spraying, the results of studies on droplet drift behaviors also suggest a method for controlling drift.