doi:10.3850/978-981-08-7724-8_11-02

ABSTRACT

Folpet belongs to an important group of sulfenimide fungicides, commonly applied on grapes, vegetables and fruit trees. In the current paper, we adopted a laboratory scale apparatus to investigate the thermal decomposition of folpet in vapour phase reactions under both oxygen rich and oxygen lean conditions, similar to those that occur in fires, burning of wood and other biomass treated or contaminated with pesticides. The apparatus consisted of a pesticide vaporiser, a tubular reactor and a sampling system designed to capture gaseous, volatile and condensable products. The analyses of gaseous species by Fourier transform infra-red spectroscopy (FTIR) determined several toxic gases including thiophosgene, phosgene (the World War I chemical agent), carbonyl sulfide, carbon disulfide and hydrogen cyanide.

The volatile organic compounds (VOC) were trapped in an activated charcoal cartridge and the condensable products were collected by XAD-2 resin cartridges and a chilled solvent trap. Performed on gas chromatography-quadrupole mass spectrometry (GCQMS), the analyses of VOC revealed the formation of tetrachloroethylene, hexachloroethane (both suspect carcinogens), benzonitrile and chlorinated benzenes. At higher temperature, the oxidation of foplet vapour produced mono to tetra, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), with PCDD/F quantified on an HRGC-MS/MS (ion trap) instrument. Combined with the experimental observations and quantum chemical calculations, we established a brief decomposition pathway of folpet. The results provide insights into combustion of folpet and allow assessing the effects of folpet fires on the environment and health.

Keywords: Folpet, Oxidative pyrolysis, VOC, Toxic gases, PCDD/F.

© 2011 CPD Unit, University of Leeds