Experimental study on photodegradation and leaching of typical pesticides in greenhouse soil from Shouguang, Shandong Province, East China

Pesticide use contributes to national food security. The dissipation pathways and degradation mechanisms of pesticides have been widely studied and pesticide residues have remained a focus of public concern. However, studies on the migration and transformation behaviors of pesticide residues in real-world greenhouse soils are insufficient. Therefore, in this study, we collected greenhouse soil from Shouguang, Shandong Province, and investigated the photodegradation and leaching of 17 common pesticides, which leave residues in the soil and are the most frequently used pesticides in Shouguang. The environmental behavior of pesticides in greenhouse soils will provide new information on pesticide residues in the real environment and provide a scientific basis for the prevention and control of pesticide pollution in greenhouse soils. The photodegradation of trifloxystrobin followed a first-order kinetic equation, whereas those of emamectin benzoate, chlorantraniliprole, buprofezin, difenoconazole, pyraclostrobin, boscalid, tebuconazole, isoprothiolane, metalaxyl, and oxadixyl followed second-order kinetics. The half-lives of 17 pesticides under light and dark conditions ranged from 2.5–104 (mean: 36.2) and 2.6–110 (mean: 31.4) days, respectively. The half-lives of emamectin benzoate, pyraclostrobin, and metalaxyl in the light were 86.6%, 68.5%, and 94.5% of their half-lives in the dark, respectively. Chlorantraniliprole, metalaxyl, nitenpyram, diethofencarb, acetamiprid, carbendazim, and oxadixyl were leached to ≥ 90% in aqueous solution. Six pesticides, avermectin B1A, emamectin benzoate, trifloxystrobin, difenoconazole, pyraclostrobin, and buprofezin, were difficult to leach from aqueous solutions. The degradation rate of some pesticides was higher in the light environment than in the dark. The leaching potential of the leachable pesticides was nitenpyram ≫ metalaxyl > acetamiprid > carbendazim > diethofencarb ≈ chlorantraniliprole > isoprothiolane > oxadixyl > boscalid ≈ tebuconazole > hexaconazole. Pesticides that are easy to leach but not easily degraded, such as chlorantraniliprole and metalaxyl, have a high potential risk of groundwater pollution, and additional degradation technologies should be used to reduce their pollution risk. The study of the photodegradation and vertical migration behavior of various pesticides is conducive to providing references for the agricultural use and pollution control of pesticides.