Soil degradation study procedure

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. 

When parathion reaches a flooded near surface site, anaerobic conditions develop. In a study on instantaneous degradation of parathion in anaerobic soils, Wahid et al. (1980) equilibrated parathion with soils previously reduced by flooding and analyzed contaminant transformation when the soils were kept in a natural state or made biologically inactive by a preautoclaving procedure. The physicochemical... 

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. 

BC was assumed to be stable on geological time scales, as charcoal particles of similar particle size were found at various depths of 65 X 10 -year-old marine sediments (Herring, 1985). Moreover, BC was found to resist various oxidation procedures, e.g., wet-chemical or thermal treatment (Kuhlbusch, 1995). Flowever, recent carboji and oxygen isotopic studies suggest that BC degrades in soils and well-oxygenated marine sediments takes less than a cen-... 

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