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Author: Shelley Jo Kauffman
Publisher:
ISBN:
Category :
Languages : en
Pages : 340
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Book Description
Author: Shelley Jo Kauffman
Publisher:
ISBN:
Category :
Languages : en
Pages : 340
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 5
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Book Description
We are investigating the role of colloids in the movement of radionuclides through water unsaturated porous media. This research is guided by a key objective of the Environmental Management Science Program (EMSP), which is to improve conceptual and predictive models for contaminant movement in complex vadose zone environments. In the report entitled National Roadmap for Vadose Zone Science and Technology [DOE, 2001], increases in the understanding of colloid-contaminant interactions, colloid mobilization, and colloid deposition within unsaturated soils are cited as requisite needs for predicting contaminant fate and distribution in the vadose zone. We seek to address these needs by pursuing three overarching goals: (1) identify the mechanisms that govern colloid mobilization, transport, and deposition within unsaturated porous media; (2) quantify the role of colloids in scavenging and facilitating the transport of radionuclides; and (3) develop and test a mathematical model suitable for simulating the movement of colloid-associated radionuclides through variably saturated porous media.
Author: Sandip Raman Patil
Publisher:
ISBN:
Category : Civil engineering
Languages : en
Pages :
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ABSTRACT: National Water-Quality Assessment Program (NAWQA) was designed just after the U.S. Geological was established. The primary objective of the NAWQA was to understand the key processes controlling contaminant fate and transport into the Nation's water resources. In particular, wide use of pesticides and fertilizers in agricultural field can impact on the quality of surface and ground waters. Contaminants can be carried to the water bodies by several ways. In colloid-facilitated transport process colloidal particles serves as a transport media for the contaminants. Colloid release from the agricultural soil under unsaturated conditions is controlled by the hydrodynamic force, capillary force and electrostatic force that is determined by the solution chemistry in terms of solution ionic strength and pH. In this research, colloid release from the agricultural soil was investigated using an intact soil column collected from an agricultural site in Gadsden County of Florida. Colloid release was monitored and the colloid release curve was simulated using an implicit, finite-difference scheme to obtain the colloid release coefficient. It was found that the hydrodynamic force and electrostatic force overcame the capillary force under the experimental conditions of this research and consequently, colloids were released. For the colloid release, solution chemistry played a key role by controlling the colloid repulsive electrostatic force within the pore system. Colloid release exponentially decreased with the increase of solution ionic strength and increased with the increase of solution pH. Colloid release was finally found to be correlated to the colloid repulsive electrostatic force within the pore system, i.e., the greater the repulsive electrostatic force, more colloids were released. In situ colloid mobilization and transport has been studied under both saturated and unsaturated conditions. In saturated conditions, the controlling parameters are solution ionic strength and pH. Colloid mobilization and transport have been modeled by the advection-dispersion equation with a first-order colloid release. The inverse version of these models can provide a platform to estimate transport parameters based on transport observations. In this research, we taken the advantages of existing contaminants transport models by fully utilizing them to investigate colloid interactions with the surrounding environment and provide parameter constraints for colloid transport modeling applications under saturated conditions. In natural systems, colloids present a potential health risk due to their propensity to associate with contaminants or in the case of certain biological colloids, inherent pathogenic nature. Although colloidal interactions have been studied for many years and much has been learned about the physical and chemical processes that control colloid retention, there still remains significant uncertainty about the processes that govern colloid release. The aim of this study was to investigate the release of in situ colloids as a function of soil depth. Colloid release from intact agricultural soil columns with variable length was investigated. Colloid release curves were simulated using an implicit, finite-difference scheme and colloid release rate coefficient was found to be an exponential function of the soil depth. The simulated results demonstrated that transport parameters were not consistent along the depth of the soil profile. Wetting agents wet hydrophobic soil by lowering the cohesive and/or adhesive surface tension, which allows the water to spread out more evenly and allows for better penetration into the hydrophobic soils. While enhancing water penetration, wetting agent applications may bring adverse impact on the soil and groundwater at the same time. The residual organic phase in the soil pores poses a long-term source of groundwater contamination. After use, residual wetting agents and their degradation products are discharged to groundwater or directly to surface waters, then dispersed into different environmental compartments. In order to assess their environmental risks, we need to understand the distribution, behavior, fate and biological effects of these surfactants in the environment. This research was designed to investigate the application of nonionic wetting agents in agricultural soils. Performance of nonionic surfactants in intact soil columns collected from agricultural soils was explored and related to the soil and wetting agent properties. In addition, the impact of the organic concentration of wetting agent fate and transport was investigated. The transport of wetting agents in the agricultural soil columns was simulated using the proposed transport models and subsequently, the effect of organic compounds on wetting agent transport was quantified.
Author: Wei Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Fate and transport of phosphorus (P) and colloidal particles in soils constitutes two major areas of inquires in contaminant hydrology. The P transport in the northeastern U.S. depends largely on P sorption of soils in variable source areas (VSAs) and land treatment systems (e.g., vegetative treatment areas [VTAs]) that receive large P applications. In this study P sorption of soils from VTAs receiving dairy farm wastewaters in New York was studied using batch P sorption experiments. A modified P sorption model that uses only Langmuir sorption isotherm was compared with a conventional model that needs both linear and Langmuir isotherms for sixteen VTA soil samples of Langford, Volusia, and Mardin channery silt loam soils. The two methods agreed well in describing P sorption, thus proving the modified model a valid tool for P sorption study. Then, the modified model was employed to study the effect of soil redox change on P sorption of an organic-rich Langford silt loam. The findings suggest that with soil redox fluctuation, invoked by alternating saturated and unsaturated soil moisture regimes, soil P sorption was enhanced by formation of freshly precipitated amorphous iron hydroxides. Colloid transport was investigated using a model colloid (carboxylated polystyrene microsphere) and a non-ideal colloid (biochar particles) in sand columns. For the model colloid, greater input concentrations lead to increased colloid retention at neutral pH in unsaturated sand, and this concentration effect was enhanced by ionic strength. This has a direct consequence for predicting the transport of colloids where the concentration decreases with depth and thus become more mobile with depth. It is expected that large quantities of biochar might be produced in the future for carbon sequestration. Therefore, the transport of biochar particles was investigated under three pH and two ionic strength levels in saturated and unsaturated sand. Biochar particles exhibited greater mobility under higher pH and lower ionic strength, and more biochar was transported by saturated flow. The biochar particles larger than 5.4% of median grain diameter were filtered out of suspension during passage through the media, whereas the retention of smaller particles was clearly dependent on solution chemistry.
Author: Veronica L. Morales
Publisher:
ISBN:
Category :
Languages : en
Pages : 169
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Book Description
Although a wide variety of studies have been conducted to understand the numerous processes responsible for the transport of solutes and particulates through soils in order to prevent groundwater contamination, many gaps remain. This thesis presents the findings of two mechanisms (colloid facilitated transport and development of preferential flow infiltration) by which contaminants are able to expedite their transport through unsaturated soils (i.e., the vadose zone), easily reach deeper groundwater, and lower the filtering capacity of soils. The first study of this thesis bridges the gap between changes in polymeric characteristics of dissolved organic matter-colloid complexes induced by solution composition, and the effect these have on colloid transport through unsaturated soils. The second study presents a semi-empirical approach to improve existing models that predict attachment efficiency ([alpha]) of electrosterically stabilized suspensions moving through a porous medium using direct measurements of polymeric characteristics. The fourth study elucidates the capillary forces responsible for the transition between pinning or allowing particles to slip when they approach an air-water-solid interface. Lastly, bioclogging and soil-water repellency from dehydrated microbial exudates are studied in terms of biotic changes in structure and surface properties that generate points of wetting instability that can result in the formation of persistent preferential flow paths.
Author: Joseph Ryan
Publisher:
ISBN:
Category :
Languages : en
Pages : 5
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Book Description
We are investigating the role of colloids in the movement of radionuclides through water unsaturated porous media. This research is guided by a key objective of the Environmental Management Science Program (EMSP), which is to improve conceptual and predictive models for contaminant movement in complex vadose zone environments. In the report entitled National Roadmap for Vadose Zone Science and Technology [DOE, 2001], increases in the understanding of colloid-contaminant interactions, colloid mobilization, and colloid deposition within unsaturated soils are cited as requisite needs for predicting contaminant fate and distribution in the vadose zone. We seek to address these needs by pursuing three overarching goals: (1) identify the mechanisms that govern colloid mobilization, transport, and deposition within unsaturated porous media; (2) quantify the role of colloids in scavenging and facilitating the transport of radionuclides; and (3) develop and test a mathematical model suitable for simulating the movement of colloid associated radionuclides through variably saturated porous media.
Author: John McCarthy
Publisher: CRC Press
ISBN: 9780873718288
Category : Technology & Engineering
Languages : en
Pages : 412
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Book Description
This valuable resource discusses several strategies of manipulating colloids for environmental restoration, identifies advantages and disadvantages of each strategy, and considers obstacles limiting the application of each strategy. Approaches evaluated include the following: Chemical modification of subsurface systems to mobilize or deposit colloids in situ Altering the mobility of microorganisms to improve delivery of microbes for bioremediation Manipulating colloids or biocolloids (bacteria) to change aquifer permeability to either enhance bioremediation or create in situ barriers Introducing modified colloids, surfactants, and emulsions to control colloid mobility or to increase recovery of sorbed contaminants by pump and treat methods Manipulation of Groundwater Colloids for Environmental Restoration also contains short, focused research reports on specific studies relevant to the various approaches under consideration. Subjects covered range from mobility of organic macromolecules by controlled field injection experiments to new techniques that investigate surface chemistry and aggregation of inorganic colloids. Other topics discussed include the depositional behavior and transport of biocolloids in porous media, surfactants as modifiers of surface binding sites on colloids, and genetic engineering of microorganisms to serve as contaminant-scavenging biocolloids. Manipulation of Groundwater Colloids for Environmental Restoration is an excellent resource for research scientists in hydrology, chemistry, and microbiology; environmental consultants; regulators; environmental engineers; bioremediation microbiologists; and engineers.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309086256
Category : Technology & Engineering
Languages : en
Pages : 433
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Book Description
Bioavailability refers to the extent to which humans and ecological receptors are exposed to contaminants in soil or sediment. The concept of bioavailability has recently piqued the interest of the hazardous waste industry as an important consideration in deciding how much waste to clean up. The rationale is that if contaminants in soil and sediment are not bioavailable, then more contaminant mass can be left in place without creating additional risk. A new NRC report notes that the potential for the consideration of bioavailability to influence decision-making is greatest where certain chemical, environmental, and regulatory factors align. The current use of bioavailability in risk assessment and hazardous waste cleanup regulations is demystified, and acceptable tools and models for bioavailability assessment are discussed and ranked according to seven criteria. Finally, the intimate link between bioavailability and bioremediation is explored. The report concludes with suggestions for moving bioavailability forward in the regulatory arena for both soil and sediment cleanup.
Author: Monzer Fanun
Publisher: Elsevier
ISBN: 0444632840
Category : Science
Languages : en
Pages : 715
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Book Description
The Role of Colloidal Systems in Environmental Protection describes the importance of colloids in many applications that contribute to environmental protection, including drinking water and wastewater treatment, heavy metal remediation, treatment of radioactive materials, corrosion, and energy conversion. Knowledge of the physical and chemical composition of colloids is important to understand and accurately model the relevant processes. The book familiarizes the reader with the technological features of the application of colloids in environmental protection, and provides chemical engineers, researchers, and scientists in academic and corporate communities with the latest developments in this field. Each chapter covers the whole spectrum of the relevant science, from the fundamentals to applications. Provides the applied technological features of colloids in environmental protection Gives insight into the use of bio-solid colloids as contaminant carriers Covers the natural occurrence of biosurfactants in the environment and their applications Provides information on the use of nanoparticles for environmental applications Chapters written by recognized and respected experts in the field from all over the world
Author: John T. Crist
Publisher:
ISBN:
Category :
Languages : en
Pages : 154
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Book Description
