Photodegradation study for assessing the environmental fate of some triazine-, urea- and thiolcarbamate-type herbicides

K. Lányi, Z. Dinya

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41 Citations (Scopus)

Abstract

Various biotic or abiotic factors influence the fate of pesticides in the natural environment, of which ultraviolet (UV) component in the sunlight is one of the most powerful forces. Studies on the photodegradation of pesticides have not only significance from the point of view of environmental science, but also very important in researching and developing new, safer, and effective pesticides. Previously we have studied the photodegradation of triazine- and urea-type herbicides in details. This paper is intended to outline the photodegradation pattern of some commonly used N-containing herbicides that belong to the groups of the mentioned triazines (atrazine, cyanazine, terbuthylazine, terbutryn) and ureas (chloroxuron, methabenzthiazuron, diuron, fenuron), as well as thiolcarbamates (butylate, cycloate, EPTC, molinate, vernolate), in order to gain information about their possible fate and derivatives in the environment. The most significant processes of photodegradation of triazines are the partial or complete loss of side-chains, or rather the substitution of the heteroatom-containing side-chain to hydroxyl-group. The chemical characteristics of the side chains determines basically the speed of the degradation. It can be concluded that the C-S bond breaks down much easier than C-Cl bond, and the chlorine atom remaining on the triazine-ring promotes the loss of alkyl-chains to a higher extent than that the hydroxy-group. In the case of ureas, the chemical properties of groups in both the N and N′ position can influence the degradation process. It could be stated the proximity of large aryl-substituent and methyl-group in the N position is unfavorable and instabilizing, promoting the further degradation of compound, at the same time, loss of these groups is the preferred degradation route. In the case of thiolcarbamates, the most frequent processes are the α- and β-oxidation of alkyl-groups connecting to the nitrogen atom. In the most cases, the N-formyl and N-dealkylated products were identified in the degradation mixture. The thioalkyl-group showed fair stability under the circumstances of photodegradation. Its partly or completely degraded products cannot be detected, and represent only very small part of the mixture.

Original languageEnglish
Pages (from-to)79-87
Number of pages9
JournalMicrochemical Journal
Volume80
Issue number1
DOIs
Publication statusPublished - Apr 2005

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Keywords

  • Environmental fate
  • Gas chromatography
  • Herbicides
  • Photodegradation
  • Thiolcarbamates
  • Triazines
  • Ureas

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy

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