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This chapter presents the composition of the petroleum-degrading microbial population of soil, the soil factors affecting the biodegradation process, the petroleum product chemical structure and its influence on the biodegradation process, and engineered bioremediation systems for treatment of petroleum products in soil. The heterogeneous or heterotrophic microorganisms found in soils include naturally occurring populations that possess the ability to degrade petroleum products. Spore-forming bacteria generally have a negligible role in biodegradation. Although Bacillus strains have been isolated from contaminated sods, this may be due to their persistence in soil and subsequent spore germination during enrichment and isolation procedures. Also, a number of actinomycetes have been shown to have hydrocarbon-degrading abilities; however, the microorganisms do not seem to compete successfully in contaminated soils. Populations of Arthrobacter and coryneforms such as Corynebacterium, Brevibacterium, Mycobacterium, and Nocardia showed strong positive responses to oil contamination. more...

This laboratory study measured growth of one plant species, Lycopersicon esculentum Big Girl (tomato), that is sensitive to the presence of soil contamination, in Kuwait soil amended with crude-oil-contaminated soil. Germinated tomato seeds were placed in containers with soil containing 0, 0.12, 0.24, 0.36, 0.48, 0.60, 1.2, and 2.4% crude oil and were grown in an indoor growth chamber. Plants grew in Kuwait soil containing up to 0.36% crude oil; however, growth and fruit production were compromised at crude oil concentrations greater than 0.12% when compared with control plants. Plants did not grow in Kuwait soil amended with 0.48% crude oil or higher. more...

The coloration changes of three soils (Amarillo sandy loam, Anthony sandy loam, and Oakville sandy loam) and two clays (kaolinite and montmorillonite) were monitored following the addition of four solvents (distilled water, unleaded gasoline, diesel fuel, and ethylbenzene) over a time period of 1 year. Soil and clay coloration was measured using Munsell color charts. In general, the Amarillo soil experienced the most extensive changes to a darker, grayer color. Initial color changes occurred in as little as 1 week, with subsequent changes occurring throughout the next 41 weeks. This study indicates that solvents can alter geologic media color and that the inferred chemical reduction processes can be an ongoing process. more...

This article presents the design of a bench‐scale reactor that has been utilized to conduct intermediate and long‐term studies on the behavior of chemicals in soil‐groundwater systems under stable Eh‐pH conditions. Also, two examples of the utilization of the reactor are discussed. more...

In situ vitrification (ISV) is a thermal treatment technology that permanently treats hazardous wastes. It was initially developed to treat soil contaminated with radioactive materials, and it is used to treat soils containing inorganic and organic chemicals. The ISV process introduces a substantial amount of energy into a relatively low-energy soil system. As a result, this energy increase affects naturally occurring processes and reactions which are governing the migration and degradation of chemicals in soil systems. This paper describes how ISV affects these naturally occurring processes and reactions. This paper concludes that although many mechanisms control chemical behavior, diffusion and convection are the main two factors that govern movement. Convection and concentration diffusion cause vaporized organic molecules to move toward the vitrified area and be destroyed or captured at the surface. Although thermal diffusion causes some molecules to move out to the transition zone up to 24 cm away, they will recondense and once again be drawn toward the vitreous zone by other mechanisms. The report also concludes that destruction mechanisms by pyrolysis and hydrolysis are also accelerated by the high temperature of the process. more...

Contaminated soils, sediments, and water , Contaminated soils, sediments, and water , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

The known degradation products and degradative pathways involving selected volatile aliphatic chlorinated hydrocarbons in soil-groundwater systems are summarized. Current data indicate that the most commonly found products of microbial degradation of these compounds come from reductive dehalogenation, while nonmicrobial degradations tend to involve hydrolysis and/or oxidation. However, conclusions must be regarded as tentative, since most of the available studies have involved model systems and extrapolations, rather than direct studies of compounds in groundwater systems. Other potentially complicating factors, such as mobility and volatilization, are mentioned. Current knowledge is discussed in the context of data that would be desirable to obtain in future studies. more...

This paper discusses soil- and clay-catalyzed oxidations in order to develop general guidelines for predicting the occurrence of these reactions. In this study, 93 organic chemicals that undergo soil- and clay-catalyzed oxidation were analyzed to identify similarities in (a) molecular structure and (b) physicochemical properties. Based on this analysis these chemicals were divided into four groups: Group 1 - aromatic chemicals that contain electron-withdrawing and weak electron-donating fragments (they have a lower water solubility limit of 200 ppm); Group 2 - aromatic chemicals that contain electron-withdrawing fragments and a very strong electron-donating fragment (lower water solubility limits is 112 ppm); Group 3 - aromatic chemicals that contain only electron-donating fragments (lower water solubility limit is 29 ppm); and Group 4 - aromatic chemicals that contain extensive conjugation (in general, these chemicals have a lower water solubility limit in the very low parts-per million to high parts-per-billion range). A hypothetical relationship between the lower solubility limit and chemical structure to chemical reactivity is proposed using simple kinetic theory. Finally, the applicability of the solubility and structure characteristics of the four groups as guidelines for predicting the occurrence of free-radical oxidation is discussed. more...

Aniline partially degraded in sterile soil to azobenzene, azoxybenzene, phenazine, form=anilide, and acetanilide. Nitrobenzene, p -benzoquinone, and unidentified species were possible products; substantial bound residues may also have formed. Soil-catalyzed conversion of aniline or [ d 5]aniline seems evidenced by 6-24X more product recovery in sterile soil than in sterile water alone, a process inhibited by Na2S2O4. Freundlich adsorption constants showed: azobenzene > azoxybenzene > phenazine > aniline. more...