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Browsing by Author "Bhandari, Alok"

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    Factors affecting binding of chlorophenols to soil
    Bhandari, Alok (Virginia Tech, 1995-07-06)
    Synthetic substituted phenols can become incorporated into soil organic matter by processes similar to natural humification. Biological, (enzyme-catalyzed), and abiotic, (mineral surface catalyzed), reactions have been implicated in these processes which result in the nonextractable binding of phenolic contaminants to soil organic matter. Experiments conducted with phenol, 4-monochlorophenol (MCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP) indicated a statistically significant difference in the degree of nonextractable binding in oxic and anoxic environments. Soils were extracted with water and methylene chloride. The extracted soils were combusted at 950°C and the 14C02 evolved was quantified as a measure of the bound contaminant. The amount of 14C02 captured during combustion of the soils indicated that approximately two times greater contaminant binding occurred in the oxic atmosphere as compared to the anoxic atmosphere. Autoclaving the soil resulted in a reduction in contaminant binding. Addition of H₂O₂ increased MCP binding by 4.5 times. The nonextractable contaminant appeared to consist of (i) a biologically coupled; (ii) an abiotically coupled; and (iii) a desorbable, but diffusion-limited component. The initial aqueous concentration of the contaminant appeared to have the greatest effect on the degree of nonextractable binding. An empirical model was developed for predicting the extent of chlorophenol binding to soil as a function of the initial aqueous concentration of the contaminant. Nearly 50% of the nonextractable 4-MCP was bioavailable to inoculated microorganisms.
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    Soil washing and post-wash biological treatment of petroleum hydrocarbon contaminated soils
    Bhandari, Alok (Virginia Tech, 1992-07-05)
    A laboratory scale study was conducted to investigate the treatability of petroleum contaminated soils by soil washing and subsequent biological treatment of the different soil fractions. In addition to soils obtained from contaminated sites, studies were also performed on soils contaminated in the laboratory. Soil washing was performed using a bench-scale soil washing system. Washing was carried out with simultaneous fractionation of the bulk soil into sand, silt and clay fractions. Cleaning efficiencies due to soil washing ranged from 60 to 81% for different soils. After washing, the finer soil particles (silts and clays) were found to possess higher concentrations of adsorbed hydrocarbons, thus requiring further treatment. Distribution of n-alkanes was studied to obtain a better understanding of contaminant redistribution and mass transfer during washing.