Deposition, dissipation, metabolism, and dietary risk assessment of chlorothalonil on pakchoi

Abstract

For the scientific application of chlorothalonil, a thorough understanding of chlorothalonil deposition, distribution, and dissipation on pakchoi is required so as to reduce its application dosage. In this study, the effects of the application dosage, application season, planting environment, initial deposition, field dissipation and metabolism of pakchoi were investigated. The chlorothalonil deposition amount gradually increased with increasing dosage and application frequency. The deposition law in each application strategy was leaf > edible parts > petiole > planting soil. The half-lives of chlorothalonil in pakchoi in May, October, and December were 2.86–5.79, 3.08–5.87, and 6.41–11.32 days, respectively. The deposition concentration and dissipation half-life of chlorothalonil in different parts of pakchoi and the planting soil in greenhouse environments were higher than those in open-field environments. The initial deposition concentration and half-life of chlorothalonil in pakchoi gradually decreased from north to south: Beijing >Hefei >Changsha in April and Hefei >Sanya in December. Chlorothalonil can be converted to metabolite I (C8HCl3N2O) in pakchoi plants, which can gradually dechlorinate to produce metabolite II (C8HCl3N2), metabolite III (C8H2Cl2N2), and metabolite IV (C8H3ClN2). Within an application interval of 7 days, the long-term consumption of pakchoi leaves and edible parts poses unacceptable dietary risks. This study improves chlorothalonil utilization rates and provides technical guidance for its scientific application in the pakchoi planting ecosystem.