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Photochemical transformation of the DDT and methoxychlor degradation products, DDE and DMDE, by sunlight

  • R. G. Zepp
  • N. L. Wolfe
  • L. V. Azarraga
  • R. H. Cox
  • C. W. Pape
Article

Abstract

DDE and DMDE, degradation products of the pesticides DDT and methoxychlor, rapidly undergo an unusual photoisomerization in solution when exposed to sunlight. The isomerization involves the exchange of a vinyl chlorine and anortho aromatic hydrogen. Other photoproducts identified were corresponding benzophenones and 1,1-diaryl-2-chloroethylenes. Quantum yields for the reactions were measured and then used to compute sunlight photolysis half-lives for DMDE and DDE. Although both compounds absorb only the short-wavelength ultraviolet component of sunlight, their photolysis was found to be surprisingly rapid. During summer at latitude 40°N, the photolysis half-lives near the surface of a water body are one hour and one day for dissolved DMDE and DDE, respectively. Photolysis of the DDE photoisomers is about an order of magnitude slower than that of DDE, suggesting that they may accumulate under environmental conditions. The DDE photoisomers photocyclize to form chlorinated dibenzofulvene and dichlorofluorenone. Neither DDE nor its photoisomers photoreact in solution to form PCB's. The environmental significance of these results is discussed, and it is suggested that the persistence of DDE in inland surface waters may be related to its tendency to sorb onto sediments and biota where no light is present.

Keywords

Hydrogen Surface Water Chlorinate Water Body Vinyl 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag New York Inc. 1977

Authors and Affiliations

  • R. G. Zepp
    • 1
  • N. L. Wolfe
    • 1
  • L. V. Azarraga
    • 1
  • R. H. Cox
    • 2
  • C. W. Pape
    • 2
  1. 1.Environmental Research LaboratoryU.S. Environmental Protection AgencyAthens
  2. 2.Department of ChemistryUniversity of GeorgiaAthens

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