Download or read book Colloid Mobilization and Transport in Contaminant Plumes written by and published by . This book was released on 1999 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloidal Transport in Porous Media written by Fritz H. Frimmel and published by Springer Science & Business Media. This book was released on 2007-05-26 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the basics of abiotic colloid characterization, of biocolloids and biofilms, the resulting transport phenomena and their engineering aspects. The contributors comprise an international group of leading specialists devoted to colloidal sciences. The contributions include theoretical considerations, results from model experiments, and field studies. The information provided here will benefit students and scientists interested in the analytical, chemical, microbiological, geological and hydrological aspects of material transport in aquatic systems and soils.

Download or read book Influences of Flow Transients and Porous Medium Heterogeneity on Colloid Associated Contaminant Transport in the Vadose Zone written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Our research is guided by an EMSP objective to improve conceptual and predictive models of contaminant movement in vadose-zone environments. As described in the report National Roadmap for Vadose-Zone Science and Technology [DOE, 2001], soil-water colloids are capable of adsorbing contaminants, such as radionuclides and metals, and facilitating their migration through the vadose zone and towards groundwater reservoirs. Our research centers on advancing understanding of this phenomenon. In particular, we are combining mathematical modeling with laboratory experimentation at pore and column scales to (1) elucidate the effects of porewater-flow transients on colloid mobilization in unsaturated porous media; (2) explore the sensitivity of colloid deposition rates to changes in porewater chemistry and colloid mineralogy; (3) develop mathematical models appropriate for simulating colloid mobilization, transport, and deposition under both steady-flow and transient-flow conditions; (4) identify mechanisms that govern mineral-colloid mobilization and deposition in unsaturated porous media; (5) quantify the effects of mineral-grain geometry and surface roughness on colloid-filtration rates; and (6) evaluate the influences of colloids on the transport of strontium and cesium (i.e., DOE-contaminants-of-concern) through soils and sediments.

Download or read book Manipulation of Groundwater Colloids for Environmental Restoration written by John McCarthy and published by CRC Press. This book was released on 1993-01-04 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Colloid and Surfactant Transport Modeling Through Agricultural Soil written by Sandip Raman Patil and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Influences of Flow Transients and Porous Medium Heterogeneity on Colloid Associated Contaminant Transport in the Vadose Zone written by Joseph Ryan and published by . This book was released on 2003 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Influences of Flow Transients and Porous Medium Heterogeneity on Colloid Associated Contaminant Transport in the Vadose Zone written by James Saiers and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Radionuclides, metals, and dense non-aqueous phase liquids have contaminated about six billion cubic meters of soil at Department of Energy (DOE) sites. The subsurface transport of many of these contaminants is facilitated by colloids (i.e., microscopic, waterborne particles). The first step in the transport of contaminants from their sources to off-site surface water and groundwater is migration through the vadose zone. Developing our understanding of the migration of colloids and colloid-associated contaminants through the vadose zone is critical to assessing and controlling the release of contaminants from DOE sites. In this study, we examined the mobilization, transport, and filtration (retention) of mineral colloids and colloid-associated radionuclides within unsaturated porous media. This investigation involved laboratory column experiments designed to identify properties that affect colloid mobilization and retention and pore-scale visualization experiments designed to elucidate mechanisms that govern these colloid-mass transfer processes. The experiments on colloid mobilization and retention were supplemented with experiments on radionuclide transport through porous media and on radionuclide adsorption to mineral colloids. Observations from all of these experiments - the column and visualization experiments with colloids and the experiments with radionuclides - were used to guide the development of mathematical models appropriate for describing colloids and colloid-facilitated radionuclide transport through the vadose zone.

Download or read book Colloids in Groundwater written by and published by . This book was released on 1992 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our originally stated objectives included: (1) development of a quantitative source function for colloid mobilization to groundwater, and (2) assessment of the most important colloidal phases to which nonpolar compounds sorb. We have been pursuing a series of studies to elucidate the roles of colloidal phases in subsurface environments. Most notably, we have discovered the critical role of secondary cementitious phases like goethite. We developed a new procedure for measuring ''surface iron oxides'' which is a great improvement over earlier methodologies. Currently, we are developing a unifying model with which we can predict the mobilization of colloids to groundwater flowing through such porous media. Also, we have been able to show that groundwater samples contain colloidal phases in sufficient quantities and of suitable properties to enhance the mobile load of toxic compounds like polycyclic aromatic hydrocarbons. Finally, we have synthesized our varied field investigations from sites in Massachusetts, New Jersey, Delaware, Nevada, Connecticut, and New York to yield a protocol for other researchers interested in evaluating colloids in groundwater. These accomplishments are discussed in more detail below. Through these efforts, we have become increasingly convinced of the central role played by colloidal phases in numerous subsurface phenomena controlling contaminant fates.

Download or read book U S Geological Survey Toxic Substances Hydrology Program Subsurface contaminationfrom point sources written by U.S. Geological Survey Toxic Substances Hydrology Program. Technical Meeting and published by . This book was released on 1999 with total page 876 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloids in Groundwater written by and published by . This book was released on 1991 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the initial project period, we have pursued several activities with the overall goal of characterizing the roles of colloid in groundwater. First, we have collected soil cores from a site where we have previously found large quantities of kaolinite colloids in the groundwater. We have intensely investigated these cores to test our hypothesis that the colloids have been mobilized as a result of iron oxide dissolution. Next, we have constructed a soil core system in our laboratory with which we are attempting to mimic the factors that we think are governing colloid transport in the subsurface. Finally, we have pursued the issue of how well organic chemicals bind to the kinds of colloids that we are seeing at field sites. Together, with our knowledge of colloid mobility, we anticipate that this sorption data will enable us to predict the influence of groundwater colloids on contaminant fates in the subsurface. Our progress in each of these activities is described in this report. 7 refs., 12 figs.

Download or read book U S Geological Survey Toxic Substances Hydrology Program written by U.S. Geological Survey Toxic Substances Hydrology Program. Technical Meeting and published by . This book was released on 1999 with total page 868 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Water resources Investigations Report written by and published by . This book was released on 1999 with total page 880 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mobilization and Characterization of Colloids Generated from Cement Leachates Moving Through a SRS Sandy Sediment written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Naturally occurring mobile colloids are ubiquitous and are involved in many important processes in the subsurface zone. For example, colloid generation and subsequent mobilization represent a possible mechanism for the transport of contaminants including radionuclides in the subsurface environments. For colloid-facilitated transport to be significant, three criteria must be met: (1) colloids must be generated; (2) contaminants must associate with the colloids preferentially to the immobile solid phase (aquifer); and (3) colloids must be transported through the groundwater or in subsurface environments - once these colloids start moving they become 'mobile colloids'. Although some experimental investigations of particle release in natural porous media have been conducted, the detailed mechanisms of release and re-deposition of colloidal particles within natural porous media are poorly understood. Even though this vector of transport is known, the extent of its importance is not known yet. Colloid-facilitated transport of trace radionuclides has been observed in the field, thus demonstrating a possible radiological risk associated with the colloids. The objective of this study was to determine if cementitious leachate would promote the in situ mobilization of natural colloidal particles from a SRS sandy sediment. The intent was to determine whether cementitious surface or subsurface structure would create plumes that could produce conditions conducive to sediment dispersion and mobile colloid generation. Column studies were conducted and the cation chemistries of influents and effluents were analyzed by ICP-OES, while the mobilized colloids were characterized using XRD, SEM, EDX, PSD and Zeta potential. The mobilization mechanisms of colloids in a SRS sandy sediment by cement leachates were studied.

Download or read book Modeling Colloid Facilitated Groundwater Contaminant Transport written by Shiyan Jiang and published by . This book was released on 1993 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloid Interactions with a Moving Air water Interface written by Surachet Aramrak and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The disposal of radionuclide wastes to the subsurface environment at Hanford Site has led us to environmental anxiety. It is not only liquid and gas phases that are responsible for contaminant transport in subsurface media, but also the solid phase itself, i.e., subsurface colloids. In the vadose zone, air-water interfaces play key roles in colloid mobilization and transport, but knowledge as to how exactly these interfaces affect colloid transport behavior is still inadequate. This dissertation reports on theoretical and experimental studies of colloid interactions with a moving air-water interface in porous media. The specific objectives of this dissertation were to (1) quantify the effect of advancing and receding air-water interfaces on detachment of colloidal particles from a solid surface, (2) quantify the effect of particle shape on particle detachment from a solid surface by a moving air-water interface, and (3) determine the effect of capillary fringe fluctuations on the behavior of colloidal particles. The major results of this work showed that air-water interfaces play a dominant role in colloid detachment surfaces. Advancing interfaces are more important in removing colloids from a stationary surface than are receding interfaces. Colloid shape affects how air-water interfaces can get pinned and angular particles are significantly better removed by moving air-water interfaces than spherical, smooth particles. These findings also apply to porous media, i.e., capillary fringe phenomena.

Download or read book The Characterization Mobilization and Transport of Surface Modified Colloids written by Joan Marie Breiner and published by . This book was released on 2003 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Role of Acidity in Mobilizing Colloidal Particulate Matter from Natural Sand Grain Surface written by Jessica Lynn Hammons and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mobilization of colloidal particulate matter (most important, clay particles) from a soil matrix in the subsurface environment is an important environmental process. As many contaminants tend to adsorb onto various colloidal mineral particles, co-transport of contaminants in association with mobilized particles could contribute significantly to the migration of these contaminants in the environment. Numerous studies have observed the effects of pH on colloid mobilization but have overlooked the possible direct role of acidity. This study looked at the role of acidity with H as a chemical agent. Through cyclic elution of a natural sand column with a weak acid and base solution, there was an increase in mobilized clay colloids. It was found that low concentrations of organic acids could assist in detaching surface clays through lysing of labile Ca2 and Mg2 ions. The H+ ions sever the chemical bonds between the grain surface and the colloidal surface by being substituted for the interstitial Ca and Mg ions. This substitution has been found to release over 1 kg of surface clay per 1 mole of H+ consumed. It was postulated that pH oscillation addition to proton dynamics could play a major role in subsurface colloid transport. The results from this study could help improve predicting of subsurface contaminant fronts and aid in managing contaminant transport in the soil water environments.