Degradation in soil

Keeping in mind the potential applications of biodegradable plastics in agricultural applications (i.e., mulching films), the characterisation of the degradation behaviour of the copolyesters in soil is currently of great interest. 

Generally, compared with composting, degradation in soil is slower and less predictable, due to lower soil temperature and variability in environmental conditions (e.g., humidity, temperature) and soil composition. 

During a 60 °C incubation in compost, the test specimen material exhibited a significant loss in MW, indicating the contribution of nonenzymatically catalysed hydrolysis (abiotic) which takes place not only at the surface, but throughout the entire material. This abiotic hydrolysis was not observed in soil burial experiments within the testing period. 

For the BTA-copolyester and PCL, the weight losses are much smaller in soil than in compost. However, for the copolyester with 55 mol% terephthalic acid, a degradation of the film of about 30% could be measured after an incubation of 10 weeks. 

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Ou L, Rao PS, Davidson JM. 1983. Methyl parathion degradation in soil Influence of soil-water tension. Soil Biol Biochem 15 211-215. 

An environmental protocol has been developed to assess the significance of newly discovered hazardous substances that might enter soil, water, and the food chain. Using established laboratory procedures and C-labeled 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), gas chromatography, and mass spectrometry, we determined mobility of TCDD by soil TLC in five soils, rate and amount of plant uptake in oats and soybeans, photodecomposition rate and nature of the products, persistence in two soils at 1,10, and 100 ppm, and metabolism rate in soils. We found that TCDD is immobile in soils, not readily taken up by plants, subject to photodecomposition, persistent in soils, and slowly degraded in soils to polar metabolites. Subsequent studies revealed that the environmental contamination by TCDD is extremely small and not detectable in biological samples. 

Mu DY, Scow KM. 1994. Effect of trichloroethylene (TCE) and toluene concentrations on TCE and toluene biodegradation and the population density of TCE and toluene degraders in soil. Appl Environ Microbiol 60 2661-2665. 

Greer LE, DR Shelton (1992) Effect of inoculant strain and organic matter content on kinetics of 2,4-dichlorophenoxyacetic acid degradation in soil. Appl Environ Microbiol 58 1459-1465. 

C]-anthracene was used to study its degradation in soil, and the formation of labeled metabolites that could be released only after alkaline hydrolysis (Richnow et al. 1998). It was possible to construct a carbon balance during the 599-d incubation, and to distinguish metabolically formed phthalate from indigenous phthalate in the soil. 

Morgan P, RJ Watkinson (1989a) Hydrocarbon degradation in soils and methods for soil biotreatment. CRC Crit Revs Biotechnol 8 305-333. 

Finally, degradation processes which are usually assumed to be first order are not. Degradation in soil has been shown by Hamaker (27) to often behave in a biphasic manner. Biodegradation in water has been shown to more closely follow second order kinet-ics(28). Photolysis in solution is highly dependent on antenua-tion of light in the water body which will depend on water quality... 

Effect of pH, soil type, and application rate on carbofuran degradation in soils... 

Table 12.2 Effect of pH, Soil Type, and Application Rate on Carbofuran Degradation in Soils... 

Processes that control degradation in soils and sediments and transformations during atmospheric transport (Swackhamer and McConnell 1993)... 

Total mercury is determined in soils containing phenylmercury acetate and or ethylmercury acetate using the method described by Polley and Miller [31]. Total mercury is determined in soils containing methylmercury chloride and methylmercury dicyanamide by the method described by Kimura and Miller [32], Kimura and Miller [30] present chemical data on the nature of residual mercurials in soil and in the atmosphere surrounding the treated soil to further elucidate the phenomena of degradation in soil. 

Brown PD, Morra MJ, McCaffrey JP, et al. 1991. Allelochemicals produced during glucosinolate degradation in soil. J Chem Ecol 17(10) 2021-2034. 

Chapman RA, Tolman JH, Cole C. 1994a. The effect of multiple soil applications of disulfoton 011 enhanced microbial degradation in soil and subsequent uptake of insecticidal chemicals by potato plants. J Environ Sci Health Part B Pest Food Contamin Agric 29(3) 485-506. 

Yagi et al. [159] reported that up to 70% of the injected methyl bromide was degraded in soil. 

Ou et al. [74] reported the enhancement of the degradation of methyl bromide in soil pretreated with an ammonia-based nitrogen fertilizer (i. e., (NH4)2S04) and stimulation of methyl bromide degradation in soil inoculated with a nitrifier, Nitrosomonas europaea. 

While degradation is slower under anaerobic conditions, evidence presented in the literature suggests that phenol can be rapidly and virtually completely degraded in soil under both aerobic and anaerobic conditions (HSDB 1997). 

Goring CA, Laskowski DA, Hamaker JW, et al. 1975. Principles of pesticide degradation in soil. In Hague R, Freed VH, ed. Environmental dynamics of pesticides. New York, NY Plenum Press, 135-172. 

Soil 2,4,5-Trichlorophenol and 2,4,5-trichloroanisole were formed when 2,4,5-T was incubated in soil at 25 °C under aerobic conditions. The half-life under these conditions was 14 d (McCall et al, 1981). When 2,4,5-T (10 pg), in unsterilized tropical clay and silty clay soils, was incubated for 4 months, 5 to 35% degradation yields were observed (Rosenberg and Alexander, 1980). Hydrolyzes in soil to 2,4,5-trichlorophenol (Somasundaram et al., 1989,1991) and 2,4,5-trichloroanisole (Somasundaram et al, 1989). The rate of 2,4,5-T degradation in soil remained unchanged in a soil pretreated with its hydrolysis metabolite (2,4,5-trichlorophenol) (Somasundaram et al., 1989). 

CASRN 61-82-5 molecular formula C2H4N4 FW 84.08 Soil When radiolabeled amitrole-5- C was incubated in a Hagerstown silty clay loam, 50 and 70% of the applied amount evolved as C02 after 3 and 20 d, respectively. In autoclaved soil, however, no C02 was detected. The chemical degradation in soil was probably via hydroxyl radicals (Kaufman et al, 1968). 

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