Record Display for the EPA National Library Catalog


Main Title Photochemical Transformation of the DDT and Methoxychlor Degradation Products, DDE and DMDE, by Sunlight.
Author Zepp, R. G. ; Wolfe, N. L. ; Azarraga, L. V. ; Cox, R. H. ; Pape., C. W. ;
CORP Author Environmental Research Lab., Athens, Ga. ;Georgia Univ., Athens. Dept. of Chemistry.
Year Published 1976
Report Number EPA/600/J-77/058;
Stock Number PB-276 199
Additional Subjects Pesticides ; DDT ; Photochemical reactions ; Photolysis ; Degradation ; Chlorine organic compounds ; Isomerization ; Insecticides ; Reprints ; Methoxychlor ; Ethane/trichloro-bis(methoxyphenyl) ; DDE insecticide ; Ethylene/bis(chlorophenyl)-dichloro ; DMDE insecticide ; Ethylene/bis(methoxyphenyl)-dichloro
Library Call Number Additional Info Location Last
NTIS  PB-276 199 Some EPA libraries have a fiche copy filed under the call number shown. 07/26/2022
Collation 11p
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 an ortho 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 degrees 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.