Abstract: Seven pesticides, including dinotefuran, difenoconazole, tolfenpyrad, chlorfenapyr, bifenthrin, diafenthiuron and glyphosate are registered and widely used as chemical pesticides on tea plants in China. These pesticides are key monitoring objects for pesticide residue risk assessment in tea. In this study, gas chromatography and ultra-high performance liquid chromatography tandem mass spectrometry were used to monitor the leaching rates of seven pesticides during green tea brewing. The results show that the leaching rates of pesticides in tea infusion were related to water solubility and octanol/water partition coefficient. Dinotefuran and glyphosate were easily soluble in water, so their average leaching rates in tea infusion were higher than 70%. The water solubilities of the other five pesticides were lower, and their average leaching rates were less than 11.3%. There were significant differences in the leaching rates of different pesticides during the first and second infusions. With the exception of bifenthrin, the average leaching rates of other six pesticides of the first infusion were 0.89-2.55 times that of the second infusion. A risk assessment of green tea made from fresh leaves 10 days after pesticide spraying was performed. According to the toxicity and human exposure risk assessment of pesticides, the risk of human health impact from ingesting seven residual pesticides through drinking green tea soup was relatively low, and the cumulative hazard quotient of the seven pesticides was only 4.1%.

Key words: tea, pesticide, tea infusion, leaching behavior, risk assessment