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A Langmuir sorption model incorporating a second step of
irreversible absorption was applied to a model soil system. The column
was packed with cellulose triacetate; pulse and step input tests with
3,4-dichlorophenol were performed; the effluent concentration was
measured by electron capture detector gas chromatography and sorption
rate constants were...
At present the adsorption kinetic of ions by soil particles is considered to be a surface reaction. When the transport of solutes in soils is described using the one-dimensional flow equation, it becomes a serious problem that lateral diffusion of ions from the bulk solution towards the soil surfaces is...
A large rainfall simulator was used to study infiltration on six
soil plots. Water content and capillary pressure were measured during
steady rainfall at rates less than required to produce runoff. The
equipment and procedures used to make these measurements are discussed.
Water content and capillary pressure data obtained as...
The formation of solution and solid complexes with heavy metals
will partially determine their mobility and plant availability in soil
systems. Experiments were initiated to determine the effect of pH,
adsorbent and initial metal concentrations, and the presence of water
soluble ligands on the adsorption of Cd and Cu by...
The reaction of F, often a component of industrial
wastes and phosphatic fertilizers, with soil was studied
with regard to sorption reactions and resultant changes in
solution composition. Sodium fluoride solutions (0.0 to
2.5 mmol/L F) were equilibrated with ten soils for 24h.
The soil extract solutions were analyzed for...
Chromium and its compounds are widely used by modern industries, resulting in large quantities of this element being discharged into the environment. To remove chromium from contaminated soils and ground water, it is necessary to predict chemical and physical processes that control the rate of reactions and transport of chromium...
Soil column studies were performed on a chromium contaminated soil from the United
Chrome Products Superfund Site currently undergoing a pump-and-treat cleanup process. The
goal of the research was to provide insight into the feasibility of chemically changing the injection
fluid of the pump-and-treat system to enhance hexavalent chromium (Cr(VI))...
Prevention of groundwater contamination by agricultural
chemicals requires an understanding of the complex
processes that control pesticide movement below the soil
surface. Through this understanding it is possible to try
to predict which areas may be most vulnerable to
contamination. The many models that have been developed to
characterize pesticide...
Experiments were conducted to study the effect of pore size
distribution on the diffusion of 2, 4-Dichlorophenoxyacetic acid (carbon-
14) through water saturated porous media. Eight size fractions of
glass beads were used representing the porous media. It was found
that as the average particle radius, and hence pore radius,...
Soil pore size distribution and water characteristics are important for water storage, water movement, and soil-plant interaction studies. Laboratory determinations of water characteristics and pore size distribution are time consuming and costly. Investigators have proposed many models to predict them from routinely available data. Most of the models are related...
Lack of stability of soil aggregates for water
movement is a major problem in arid soils due to low
organic matter and higher sodium contents. Soil
amendments for improving stability of structure and
increasing infiltration of water are essential to solve
water management problems in these areas.
Different rates of...
Chromium, an element of widespread use, is toxic in some
forms. Improper disposal of waste chromium products has
resulted in contamination of many sites throughout the United
States, including the United Chrome Products Superfund site
in Corvallis, Oregon. A better understanding of chromium
chemistry is needed to facilitate the remediation...
The emission of sulfur oxides from anthropogenic sources represents a potential threat to terrestrial ecosystems. Sulfate, the most highly oxidized form of sulfur, is the most common form of inorganic sulfur in most soil environments. The sorption of sulfate may influence the alkalinity of the soil solution and as a...
Tile drainage increases aeration in the root zone of poorly drained soils by
accelerating water movement from the subsurface. Water movement is the main agent
of chemical transport, either transporting soluble materials directly (e.g., nitrate) or by
transporting the soil particles that bind adsorptive compounds (e.g., pesticides). The
detection frequency...
Vertisols and other vertic-intergrade soils are found all over the globe, including many agricultural and urban areas. These soils are characterized by their cyclical shrinking and swelling behaviors, where bulk density and porosity distribution both vary as functions of time and/or soil moisture. In turn, alterations in physical soil parameters...
Chromium spills on soils are causing severe groundwater contamination
problems. To increase the performance of cleanup methods, the chemical behavior
of chromium in soils and its transport through soils have to be understood. The
objectives of this research were to investigate the sorption characteristics of
chromium(VI) in soil and to...
An experimental and numerical modeling investigation was conducted to study interactions between microbial dynamics and transport processes in variably saturated porous media. These interactions are important in a variety of applied problems such as water and wastewater treatment, bioremediation, and oil-field recovery operations. These processes and interactions also have great...
Four factors govern the potential for groundwater
contamination by pesticides passing through the soil:
• Properties of the soil
• Properties of the pesticide
• Hydraulic loading on the soil
• Crop management practices
This thesis explores open questions regarding molecular forms and interactions of natural and synthetic aromatic compounds present in soils and sediments.
Plant biomass-derived black carbon (biochar) generated through incomplete natural and anthropogenic combustion processes is a major source of aromaticity in terrestrial ecosystems. Chapter one represents a detailed account of...
Information about forest substrate respiration, nitrogenase activity and
mineralizable nitrogen may be incorporated into carbon and nitrogen budgets that comprise an important element of forest management planning. In this study, substrate respiration, nitrogenase activity and mineralizable nitrogen were measured in two western Oregon Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stands within...
Many different models and mechanisms of water imbibition into soil have been described in the literature. Theoretical equations based on those models exist to predict how water will flow in porous media. These models can be useful, but have their weaknesses. Research on imbibition and infiltration into soils has mostly...