Stability of contact insecticides. IV.—Relationship between the ultra‐violet absorption spectrum and the photolysis of DDT and the pyrethrins

Abstract

The ultra-violet photolysis of DDT and the pyrethrins was investigated with selected wavebands in the middle and near ultra-violet. Severe decomposition is caused by light strongly absorbed by both insecticides at zroo-zqoo A. DDT is not affected by other parts of the spectrum, but the pyrethrins are slowly decomposed by radiation between 2400 A and the visible region. probably by a light-catalysed oxidation rather than direct photolysis. DDT, like the pyrethrins, undergoes rapid photolysis in strong sunlight, suggesting that traces of light of the waveband 2200--2qoo A may penetrate to the earth's surface.

Associated decomposition of DDT to DDE in the diffusion of DDT on homoionic clays

“…Decomposition of DDT also occurs in plant tissues (Findley and Fillmore, 1963) and in animal tissues (Nasir, 1953; Peterson and Robinson, 1964; Wasserman etal., 1965). The most abundant metabolite is DDE, but several other metabolites also appear (Peterson and Robinson, 1964).…”

“…The conclusion has been reached that the stability of DDT in the soil is related to the type of soil (Ginsburg, 1952) and the chemical composition of the soil (Fleck and Haller, 1944;Fleck et at., 1945;Fowkes et al, 1960). The stability of DDT in the soil also depends on moisture (Harris, 1964;Weidhaas et al, 1961), on the temperature of the soil (Birrell, 1963;Cutkomp, 1947;Gunther and Tow, 1946;Lichtenstein and Schultz, 1959), and on the quantity of visible radiations (Chisholm and Koblitsky, 1947;Ginsburg, 1952;Nurova, 1953) and ultraviolet radiations (Mitchell, 1961;Nasir, 1953). Due to the influence of these factors, the main decomposition product of DDT is DDE, although l,chloro-l,hydroxy-2,2,bisfp-chlorophenylethylene) and many others of less importance have been identified.…”