Decomposition polluted soils

The long-lasting damaging effect of cyanide may be mainly determined whether its sorption on soil or sediment is reversible or not. If the adsorption is reversible and quick, no pollution will remain after the polluted stream passes. If the sorption is irreversible, the sorbed cyanide becomes the source of pollution later, with the decomposition of soil components. The desorption of cyanide was examined in two soil and two sediment samples (Tiszavasvari and Tiszalok). The samples were chosen in such... 

Farquhar G.J. Rovers S.A. Gas Production from Landfill Decomposition Water, Soil and Air Pollution 2 1973,493. 

Berg, B., Ekbohm, G., Soderstrom, B., and Staaf, H., Reduction of decomposition rates of Scots pine needle litter due to heavy-metal pollution, Water, Air, Soil Pollut, 59 (1), 165-177, 1991. 

In addition to the simple Eh-pH graph shown in Figure 9.3, three-dimensional Eh-pH graphs can be produced. Known quantities of a pollutant can be added to a number of different soil suspensions and its degradation at different combinations of Eh and pH measured. In this way, the optimum conditions for the decomposition of the pollutant in question can be determined. An excellent example of this is the decomposition of pentachlorophe-nol and hexahydro-l,3,5-trinitrol,3,5-triazene in soil and water under various Eh-pH conditions as illustrated in the papers by Petrie et al. [9] and Sing et al. [10]. 

Baker MD, Mayfied Cl. 1980. Microbial and nonbiological decomposition of chlorophenols and phenol in soil. Water Air Soil Pollut 13 411-424. 

Figure 12.8 shows an example of parathion distribution in sterilized and natural, biologically active Gilat soil columns. We see that, at relatively early times, when the effect of decomposition is minimal, the parathion distribution is similar to that in the sterile soil. After four days, the effect of microbial activity on decomposition is evident, and the distribution pattern is significantly different. After seven days, the parathion is almost completely decomposed. This example emphasizes the necessity to consider additional processes, snch as degradation, in analyses of pollutant transport. 

In the late 1970s HPLC provided an ideal tool for the analysis of pollutants and other environmental contaminants. Techniques were developed for analyzing chlorophenols, pesticide residues, and metabolites in drinking water and soil (parts per trillion) and trace organics in river water and marine sediments, and for monitoring industrial waste water and polynuclear aromatics in air. Techniques were also developed for determining fungicides and their decomposition products and herbicide metabolites in plants and animals. 

Soil pollutants may percolate and end up in ground-water, or be retained by a soil matrix due to their affinity for specific soil components (e.g., insoluble organic compounds in humic substances). There, they may stay inactive, decompose, or react with soil components or with other pollutants. Reactions from these types of pollutants with soil include oxidation, reduction, combination, precipitation, dissolution, and metathesis. The main decomposition pathways include biodegradation (see Section 9.1.2), chemical degradation, and... 

One of the more recent technologies in pollution treatment and remediation is based on the electrokinetic decontamination of soils [126-128], in which a dc potential (a few volts per centimeter) is applied across two inert electrodes embedded in a soil mass. This applied potential causes decomposition of the soil water to occur at the two electrodes. The migration of contaminants in the electric field, water transport, and reactions at the electrodes, as well as reactions caused by the induced pH gradient, can effectively clean soils. Acar et al. [127] reviewed electrokinetic remediation for the removal of metals and other inorganic contaminants from soil as well as its use in the extraction of organics from contaminated soils. 

Groundwater analysis, determination of pollutants from abandoned armaments in soils and surface waters, decomposition products from azo dyes used in textiles. 

PCBs are extremely stable to heat, chemical, and biological decomposition. They are excellent insulating and cooling fluids, extensively used for many years in manufacture of transformers and capacitors. PCBs are also used in hydraulic fluids, lubricating oils, paints, adhesive resins, inks, fire retardants, wax extenders, and numerous other products. The chemical and physical properties of PCBs make the remediation of polluted sites difficult. They resist degradation and absorb into soils and colloidal materials in water. Some persist with half-lives of 8-15 years in the environmental compartments. This stability contributes to their dispersion in the environment and long-range air pollution. Because they are lipophilic, these species are stored in fatty tissues and accumulate in the food webs (see Section 2.2). 

Very often compounds being extracted by superheated water react in the medium by hydrolysis or otherwise. It is know from other studies involving pure contaminants that they will react, for example chlorinated hydrocarbons are often dechlo-rinated and converted into hydrocarbons. In other cases benign materials are obtained from pollutants. In the extraction of the explosives TNT, RDX and HMX from contaminated soil, decomposition occurs non-dramatically and completely to benign substances [48]. These compounds contain an oxidative reagent within the molecule. Soil obtained from a bomb disposal site contaminated with 120 000 ppm (12%) of TNT, after treatment in a static ceU at 275°C for 1 h, contained only 2 ppm and the water remaining 4 ppm. Dioxins in contaminated soil treated for 4 h at were found to be reduced by 99.4%, 94.5% and 60% at temperatures of 350°C, 300°C and 150°C, respectively [49]. 

Farquhar, G.J. Rovers, R.A. "Gas Production During Refuse Decomposition", Water, Air and Soil Pollution 1973, 2. 483-95. 

Fairbank (1994) Recycling - the inevitable reality. IWM Proceedings, July, 22-24. Farquhar, GJ. and Rovers, F.A. (1973) Gas production during refuse decomposition. Water, Air, and Soil Pollution, 2, 483-495. 

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