US EPA

2202260 

Journal Article 

Vapor-phase photodecomposition of DDT 

Crosby, DG; Moilanen, KW 

1977 

Yes 

Chemosphere
ISSN: 0045-6535
EISSN: 1879-1298 

6 

4 

167-172 

English 

10.1016/0045-6535(77)90130-8 

In an effort to determine whether sunlight may play an important role in the environmental destruction of DDT and DDE, the possible photolyzation of these compounds in the vapor state was studied. The UV irradiation of DDT resulted mainly in the formation of DDE with much smaller amounts of DDD and traces of other volatile substances. The half-life of DDT was about 6 days, but DDD vapor appeared stable to light. DDE vapor decomposed relatively slowly in light to yield primarily DDMU and DCB (4,4'-dichlorobenzophenone), although small proportions of at least 7 other products were also observed. Irradiation of DDMU in the photoreactor gave primarily DCB, while DCB in turn slowly formed dichlorobiphenyl; the chlorinated biphenyls were stable to irradiation in the vapor phase. The photochemical formation of simple chlorobiphenyls from DDT or DDE in solution has been noted in several previous investigations. That they do not occur appreciably in the environmental samples must be due both to their volatility and to their rapid photodecomposition in solution. Ambient air samples from Davis, California provided gas chromatograms with peaks corresponding to those of DDT, DDD, DDE (or its isomer) and DCB, but amounts were too small for mass spectrometric identification of PCB isomers.