US EPA

2206779 

Technical Report 

Studies on ecological chemistry. Part 105. Photomineralization of certain aromatic xenobiotics 

Gaeb, S; Nitz, S; Parlar, H; Korte, F 

1975 

PESTAB/75/2589 

4 

4 

251-256; 1975 

PESTAB. The behavior of hexachlorobenzene, pentachlorobenzene, PCP, DDT, DDE, 2,4,5,2',4',5'-hexachlorobiphenyl, and 2,5,2',5'-tetrachlorobiphenyl in the presence of a large excess of oxygen exposed to UV-light with wavelengths 2z 230 nm (quartz glass) as well as with wavelengths 2z 290 nm (pyrex glass) was investigated. It was noted that the conversion rates of the substances adsorbed on particulate matter were far higher than with those deposited as solids or thin films on a glass surface. These differences are attributed to the bathochromic shift, changes in the relative extinction or appearance of new absorption bands as a consequence of the adsorption on silica gel, and greater dispersion of pesticide molecules in the adsorbed phase resulting in greater pesticide/oxygen contact. The disappearance of the applied substances can neither be explained by the vapor pressure of substances nor is it due to the formation of photoproducts. Since carbon dioxide and hydrochloric acid are formed during pyrex lamp irradiation of PCP, DDT, and DDE as solids on glass and the UV-absorption bands of these compounds are located nearly in the same region as those of the substances adsorbed on silica gel, it is deduced that in this case mineralization products are evolved. Measurements of the reaction rates leading to mineralization by means of application of labeled compounds are currently under investigation.