Soil and glass surface photodegradation of etofenprox under simulated california rice growing conditions

Martice Vasquez, Thomas Cahill, Ronald Tjeerdema

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Photolysis is an important degradation process to consider when evaluating a pesticide's persistence in a rice field environment. To simulate both nonflooded and flooded California rice field conditions, the photolytic degradation of etofenprox, an ether pyrethroid, was characterized on an air-dried rice soil and a flooded rice soil surface by determination of its half-life (t 1/2), dissipation rate constant (k) and identification and quantitation of degradation products using LC/MS/MS. Photodegradation was also characterized on a glass surface alone to rule out confounding soil factors. Measured photolytic dissipation rates were used as input parameters into a multimedia environmental fate model to predict etofenprox persistence in a rice field environment. Photolytic degradation proceeded at a faster rate (0.23/day, t 1/2 = 3.0 days) on the flooded soil surface compared to the air-dried surface (0.039/day, t 1/2 = 18 days). Etofenprox degradation occurred relatively quickly on the glass surface (3.1/day, t 1/2 = 0.23 days or 5.5 h) compared to both flooded and air-dried soil layers. Oxidation of the ether moiety to the ester was the major product on all surfaces (max % yield range = 0.2 ± 0.1% to 9.3 ± 2.3%). The hydroxylation product at the 4′ position of the phenoxy phenyl ring was detected on all surfaces (max % yield range = 0.2 ± 0.1% to 4.1 ± 1.0%). The air-dried soil surface did not contain detectable residues of the ester cleavage product, whereas it was quantitated on the flooded soil (max % yield = 0.6 ± 0.3%) and glass surface (max % yield = 3.6 ± 0.6%). Dissipation of the insecticide in dark controls was significantly different (p < 0.05) compared to the light-exposed surfaces indicating that degradation was by photolysis. Laboratory studies and fate model predictions suggest photolysis will be an important process in the overall degradation of etofenprox in a rice field environment.

Original languageEnglish (US)
Pages (from-to)7874-7881
Number of pages8
JournalJournal of Agricultural and Food Chemistry
Volume59
Issue number14
DOIs
StatePublished - Jul 27 2011

Keywords

  • Insecticides
  • etofenprox
  • level IV fugacity model
  • photolytic degradation
  • pyrethroids
  • soil surface

ASJC Scopus subject areas

  • Chemistry(all)
  • Agricultural and Biological Sciences(all)

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