Insights on leaching, adsorption–desorption of spirotetramat and its four metabolites on “Third Pole” pollution-free area:Qinghai–Tibet Plateau

The use of pesticides has led to increased soil and water pollution, which has even affected the world's third pole, the Tibetan Plateau. In this study, the adsorption and desorption experiments of spirotetramat on three typical soils were conducted to investigate the migration and leaching risk of pesticides in the Qinghai-Tibet Plateau ecosystem. We used batch equilibrium technique for adsorption-desorption experiments and evaluated leaching risk by computational simulation experiments under laboratory conditions. The Freundlich adsorption constants K_f of spirotetramat in the soils of Haidong, Haixi and Haibei were as follows: At 22.26, 15.13 and 6.85, the maximum adsorption capacity C_max was 434.80, 217.40 and 169.50 mg kg^-1, the average adsorption rates were 77.92, 54.27 and 39.13 %, and the desorption constants (K_f) were 43.27, 22.35 and 11.56, respectively. The hysteresis coefficient HI>1.00 in the soil of Haidong and Haixi, and 0.70<HI<1.00 in the soil of Haibei, indicating that with the increase of temperature, the adsorption capacity of the tested soil for spirotetramat decreases, which increases the migration risk of pesticides. The desorption of spirotetramat in the soil of Haidong and Haixi has a lag. The GUS values of spirotetramat in the soils of Haidong, Haixi and Haibei were 1.15, 1.63 and 1.72, respectively, which were all lower than 1.80, indicating that spirotetramat was a non-leaching pesticide, and the leaching risk of spirotetramat in the soils of Qinghai was small, and the potential harm to groundwater was at a low level.