Oxygen, soil

Moisture content/field capacity Depth to impacted (contaminated) area Groundwater depth Dissolved oxygen Soil gas... 

The flow of water through soil is called percolation. The more porous the soil, the greater the rate of percolation. With excessive percolation, flowing water removes many water-soluble nutrients needed to make the soil productive. This process is known as leaching. With too little percolation, topsoil becomes waterlogged, choking off a plants supply of oxygen. Soils with optimal percolation drain water from all but the smallest air pockets. 

H0jberg O., Revsbech N. P., and Tiedje J. M. (1994) Denitrification in soil aggregates analyzed with microsensors for nitrous oxide and oxygen. Soil Sci. Soc. Am. J. 58, 1691-1698. 

Gregory, R.G. and Durrance, E.M., 1985. Helium, carbon dioxide and oxygen soil gases small scale variations over fractured ground. J. Geochem. Explor., 24 29-49. 

The environmental degradation of lubricating oils is less easily demonstrated. One of the problems is the complex and varied nature of the used material. Materials other than hydrocarbons can inhibit or influence the rate of degradation, which is of greatest interest. Once released into the environment, there is a finite time before the waste lubricant is bound up in sediments or soils. Once there, due to the hydrophobic nature of the material, water is excluded and conditions are essentially anoxic. Anaerobic degradation of oils does not readily occur in nature - much to the relief of the oil exploration and refining industry. However, waste lubricant on the road or in soil or sediments is not locked in place in the same way as crude oil in rock formations. Heavy rain can wash surfaces, churn up river beds and release sediments, whilst the action of animals and plant can oxygenate soils. One means of... 

Daimler Benz, Ulm in cooperation with the Fraunhofer Institute (ICT) are setting up a process for the treatment of electronic scrap [27]. Technical University Munich operated a bench-scale SCWO-plant of 50 kg/h for the treatment of waste that could not be destroyed by biological systems. In these experiments, various model compounds were treated with hydrogen peroxide. These activities were terminated in 1996 [28]. Technical University Hambing Harbmg developed the combined process of soil extraction [29] followed by SCWO with electrolytic in-situ generation of oxygen. Soil was taken from a former paint factory, clay loam and other contaminated sites. 

FIG. 4—A metallic pipe Is anodic In wet soli with lower oxygen content and cathodic in better oxygenated soil. 

Relationships betv/een ethylene, oxygen, soil moisture content and temperature. Journal of Soil Science, 2, 217-230. 

A commercial technology (69), the SABRE process, treats contaminated water and soil ia a two-stage process by adding a readily degradable carbon and an inoculum of anaerobic bacteria able to degrade the contaminant. An initial aerobic fermentation removes oxygen so that the subsequent reduction of the contaminant is not accompanied by oxidative polymerization. 

Lead is one of the most stable of fabricated materials because of excellent corrosion resistance to air, water, and soil. An initial reaction with these elements results in the formation of protective coatings of insoluble lead compounds. For example, in the presence of oxygen, water attacks lead, but if the water contains carbonates and siUcates, protective films or tarnishes form and the corrosion becomes exceedingly slow. 

Ex situ bioremediation may use various biological wastewater treatment processes, soil piles, or land appHcation. With in situ bioremediation, the basic process is the same microbes, soil, and water working together as a bioreactor. Where the in situ techniques differ are in how contaminants and microbes are brought in contact and how oxygen, nutrients, and other chemical supplements ate distributed in the soil—water—air matrix. Typical in situ bioremediation techniques include natural or intrinsic attenuation, air sparging, and bioventing. 

In Situ Bioremediation. In situ bioremediation can be an aerobic or anaerobic process, or a combination of the two. In designing an in situ bioremediation system, one should consider the types of microorganisms available (naturally in place or added), the stmctural and chemical makeup of the soil matrix, types of contaminants, oxygen and nutrient addition and distribution, and temperature. These factors are discussed prior to introducing the individual techniques for in situ bioremediation. 

Design Considerations. The effectiveness of in situ bioremediation is influenced by many factors, including microorganisms, soils, oxygen, pH, temperature, type and quantity of contaminants, and nutrients. 

On the downside, various studies (23—25) have shown that hydrogen peroxide decomposes rapidly after soil contact, it is cytotoxic at a 3% solution and unless stabilized, oxygen bubbles can escape prematurely through the unsaturated zone before they have a chance to disperse well in the ground water. 

R. N. Miller, "A Field-Scale Investigation of Enhanced Petroleum Hydrocarbon Biodegradation ia the Vadose Zone Combining Soil Venting as an Oxygen Source with Moisture and Nutrient Addition," doctoral dissertation submitted to the Civil and Environmental Engineering Department,... 

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