Sunlight degradation

In soil, alachlor is photolytically unstable. After an 8-h exposure to sunlight, degradation yields in a sandy loam, loam, silt loam, and clay were 22, 27, 36, and 39%, respectively. Degradation appeared to be enhanced in soils having low organic carbon content and low pH (Fang et al., 1979). 

Pelizzetti et al. (1990) investigated the photocatalytic degradation of atrazine in solution in the presence of suspended titanium dioxide as a catalyst under simulated sunlight. Degradation was rapid but mineralization did not occur. Intermediate compounds included 6-hydroxy-A/-ethyl-/V -(l-methylethyl)-5 triazine-2,4-diamine, 2,4-diamino-6-chloro-A/-(l-methylethyl)-5-triazine, 2,4-di-amino-6-chloro-/V-ethyl-5-triazine, 2,4-diamino-6-chloro-5-triazine, 2,4-diamino-6-hydroxy-5-tri-azine, 2-amino-4,6-dihydroxy-5-triazine, 2-amino-4-hydroxy-6-chloro-5-triazine, 2,4-dihydroxy-6-chloro-s-triazine, 6-chloro-/V-acetyl-/V -(l-methylethyl)-5-triazine-2,4-diamine, and cyanuric acid as the final product. 

Figure 3. Sunlight degradation products of commercial MCPA dimethylamine salt formulation in aqueous spray droplets.

Figure 5. Sunlight degradation products of TCDD in mixed butyl esters of 2,4-D and 2,4,5-T as a deposit on a leaf surface ...

Figure 6. Sunlight degradation products of carbaryl and dieldrin on surfaces or as vapor.

Figure 8. Sunlight degradation products of molinate as atmospheric vapor (a) compared to natural water (w) containing oxidant.

Cellulose. It has been known for about one hundred years that sunlight degrades cellulose (43), and much work has been done on the photochemistry of cellulose (35,43-450). 

Carbodiimides can be used as stabilizers in thiophosphate based pesticides to prevent hydrolytic degradation. Some carbodiimides show insecticidal and acaricidal properties. Diafenthiuron [l-t-butyl-3-(2,6-diisopropyl-4-phenoxyphenyl)thiourea], an effective insecticide and acaricide, may act via its derived carbodiimide. This transformation is accomplished by sunlight degradation in aqueous solution. The carbodiimide causes inhibition of ATP phosphorylation. An H-labeled derivative of diafenthiuron, [phenoxy-4- H]diafenthiuron, has been prepared to study its photochemical and metabolic degradation. " The biological activity of N-(pyrid-3-yl)thioureas toward spider mites is sensitive to the kinetics of the formation of the carbodiimides and their photochemical stability. ... 

D. Hongve (1994). Sunlight degradation of aquatic humic substances. Acta Hydro-chim. Hydrobiol, 3,117-120. 

Fig. 21. Absorption spectra of sunlight degraded delustered nylon-6,6 yarns (exposure time up to five months) in 8 N hydrochloric acid [reproduced with permission from Ref. 105],...

No consistent relationship was found between age and cystine content. Although factors such as diet (malnutrition), cosmetic treatment, and environmental effects (sunlight degradation) may have contributed to variation among these samples, such factors were not considered in this study. 

Let us examine for a moment the implications of one of the new requirements. Pesticides shall be classified for restricted use if in general use unreasonable adverse effects on the environment may occur. A number of formidable questions readily come to mind What constitutes an unreasonable adverse effect What tests are appropriate for the detection of an adverse environmental effect - tests on which organisms - at what levels of exposure - for how long One cannot adequately judge the potential adverse effects of a chemical unless the fate of the compound in the environment is known. Is it photo-lyzed by sunlight - degraded by soil bacteria - taken up by plants - consumed by animals Is it translocated, volatilized or bound to soil Is it persistent One question leads to another ad infinitum. It was clear that some criteria would... 

Section 3 Developing Formulations of Microbial Pesticides to Resist Sunlight Degradation... 

H-benzotriazol-2 -yl)phenols (35) are used as ultraviolet absorbers, particular for the protection of important synthetic fibres against sunlight degradation. The triazoles are usually produced by reduction of the corresponding o-nitrophenylazo dyes (34), using a wide variety of reducing systems [53]. The first catalytic synthesis has been recently reported (eq. 14, Table 13) [53] ... 

Poly(tetramethyIene diselenide) in chloroform solution at 60 °C or in the presence of diffused sunlight degrades to form 1,2-diselenane [218] and when heated stron y it forms selenolane [214] ... 

Table 3 Effect of Anthraquinone Vat Dyes on the Sunlight Degradation of Fibres...

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