Enhanced degradation confirmation

Field studies with single applications of phenoxyalkanoic acid herbicides have indicated that breakdown is rapid under temperature and moisture conditions that favour microbiological activity (5). Enhanced degradation of these herbicides, under field conditions, was first noted in the late 1940s. The use of plant bioassay procedures, led to the discovery that the persistence of 2,4-D, but not 2,4,5-T, was decreased,by pretreatment of the soil with 2,4-D (26, 27). This enhanced breakdown was later confirmed using (14C)2,4-D and radiochemical analytical techniques (29). The breakdown of the (14C)2,4-D being more rapid in soil from the treated plots, tested 8 months after the last field application, than in soil from plots treated for the first time. 

All soils from fields previously treated with carbofuran exhibited a much higher mineralization rate than soils from non-history fields. Previous reports have confirmed the enhanced degradation of carbofuran, and its rapid mineralization In each carbofuran-hlstory soil is Indicative of Its great susceptibility to enhanced degradation. Even the fencerow soils surrounding carbofuran-history fields exhibited increased carbofuran mineralization rates, and had apparently been contaminated by carbofuran or carbofuran-treated soli. Up to 5 years had elapsed since the last carbofuran soil application to history soils. 

At temperatures above Tm, chemical and enzymatic degradation of microbial exopolysaccharides is enhanced. The apparent enhanced stability of microbial exopolysaccharides in their ordered confirmation is thought to be due to the glycosidic bonds in the backbone of the polymer which raises the activation energy. This restricted movement would also restrict access of enzymes and chemicals to the backbone. 

It is usually accepted that the augmentation of the XO activity in ischemic tissues undergoing reperfusion is a consequence of the formation of hypoxanthine from degradation of ATP in the presence of dioxygen. It has been confirmed by Xia and Zweier [55] who studied the mechanism of stimulation of the XO-catalyzed superoxide production in postischemic tissues. It was found that an increase in superoxide production in isolated rat hearts after reperfusion was triggered by the enhancement of hypoxanthine and xanthine levels due to the degradation of ATP during ischemia. 

Since we still observed increased rates in the absence of inhibitor and in the presence of ultrasound (Fig. 5.35) we have explained the reduction or lack of an induction period in the presence of ultrasound in terms of two factors namely, a greater radical production both from enhanced initiator breakdown [74], and/or degradation of the polymer, and also from the creation of a far more stable emulsion. This latter point was confirmed visually. Depending upon the irradiation power and surfactant level employed, we were able to observe up to 40 % increase in initiator breakdown and a de-... 

---