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Biogeochemical reactions promoted by reactive mineral species and bacteria in sediment and groundwater influence the fate of environmental contaminants. Enhanced reductive transformations of chlorinated ethenes, a class of persistent contaminants, have been observed in biologically active systems relative to analogous abiotic systems. While some reactions mediated by bacteria are more efficient than abiotic reactions, biological dechlorination of chlorinated ethenes can yield byproducts that are no less toxic than the original contaminant. Chlorinated ethenes are remarkably challenging to remediate in aquifers with low permeability zones (LPZs), such as silts and clays. This dissertation explores the biotic and abiotic contributions to trichloroethene (TCE) transformation during back diffusion from LPZs into adjacent high permeability zones (HPZs). These contributions are quantified with flow cell experiments that represent the LPZ/HPZ interface using clay and sand from a field site. Flow cell data informed development of a numerical diffusion-reaction model, and back diffusion during biotic and abiotic TCE transformation was simulated. Both pathways occurred simultaneously in the flow cell, with biotic processes transforming more TCE mass than abiotic processes in the presence of electron donor. Simulations constrained to abiotic reactions demonstrated that reactive minerals can decrease TCE flux from LPZs by 2-53% over two years, depending on the mineral type. TCE attenuation of this magnitude highlights the potential for abiotic transformations in some contaminated aquifers. Other biologically mediated reductive reactions promote formation of minerals that abiotically transform TCE to innocuous compounds. The role of both sulfate and iron reducing bacteria in forming and maintaining reactive iron sulfide minerals was evaluated. Reduction potential significantly influenced TCE transformation kinetics, with more negative potentials correlating with more iron sulfide precipitation and higher TCE transformation rates. Coprecipitation of other mineral species at less negative potentials contributed to diminished TCE transformation. XPS and XRD data paired with MINTEQ calculations informed conclusions about experimental precipitate reactivity. Prior to this work, no study had shown that mineral-promoted abiotic reactions could attenuate TCE in LPZs. It is also the first time that correlations between redox potential, mineral stability, and TCE transformation kinetics have been evaluated for biogenic iron sulfides with varied iron concentrations
This is the first complete edited volume devoted to providing comprehensive and state-of-the art descriptions of science principles and pilot- and field-scaled engineering applications of nanoscale zerovalent iron particles (NZVI) for soil and groundwater remediation. Although several books on environmental nanotechnology contain chapters of NZVI for environmental remediation (Wiesner and Bottero (2007); Geiger and Carvalho-Knighton (2009); Diallo et al. (2009); Ram et al. (2011)), none of them include a comprehensive treatment of the fundamental and applied aspects of NZVI applications. Most devote a chapter or two discussing a contemporary aspect of NZVI. In addition, environmental nanotechnology has a broad audience including environmental engineers and scientists, geochemists, material scientists, physicists, chemists, biologists, ecologists and toxicologists. None of the current books contain enough background material for such multidisciplinary readers, making it difficult for a graduate student or even an experienced researcher or environmental remediation practitioner new to nanotechnology to catch up with the massive, undigested literature. This prohibits the reader from gaining a complete understanding of NZVI science and technology. In this volume, the sixteen chapters are based on more than two decades of laboratory research and development and field-scaled demonstrations of NZVI implementation. The authors of each chapter are leading researchers and/or practitioners in NZVI technology. This book aims to be an important resource for all levels of audiences, i.e. graduate students, experienced environmental and nanotechnology researchers, and practitioners evaluating environmental remediation, as it is designed to involve everything from basic to advanced concepts.
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.
In the past decade, officials responsible for clean-up of contaminated groundwater have increasingly turned to natural attenuation-essentially allowing naturally occurring processes to reduce the toxic potential of contaminants-versus engineered solutions. This saves both money and headaches. To the people in surrounding communities, though, it can appear that clean-up officials are simply walking away from contaminated sites. When is natural attenuation the appropriate approach to a clean-up? This book presents the consensus of a diverse committee, informed by the views of researchers, regulators, and community activists. The committee reviews the likely effectiveness of natural attenuation with different classes of contaminants-and describes how to evaluate the "footprints" of natural attenuation at a site to determine whether natural processes will provide adequate clean-up. Included are recommendations for regulatory change. The committee emphasizes the importance of the public's belief and attitudes toward remediation and provides guidance on involving community stakeholders throughout the clean-up process. The book explores how contamination occurs, explaining concepts and terms, and includes case studies from the Hanford nuclear site, military bases, as well as other sites. It provides historical background and important data on clean-up processes and goes on to offer critical reviews of 14 published protocols for evaluating natural attenuation.
In the late 1970s and early 1980s, our nation began to grapple with the legacy of past disposal practices for toxic chemicals. With the passage in 1980 of the Comprehensive Envir- mental Response, Compensation, and Liability Act (CERCLA), commonly known as Sup- fund, it became the law of the land to remediate these sites. The U. S. Department of Defense (DoD), the nation’s largest industrial organization, also recognized that it too had a legacy of contaminated sites. Historic operations at Army, Navy, Air Force, and Marine Corps facilities, ranges, manufacturing sites, shipyards, and depots had resulted in widespread contamination of soil, groundwater, and sediment. While Superfund began in 1980 to focus on remediation of heavily contaminated sites largely abandoned or neglected by the private sector, the DoD had already initiated its Installation Restoration Program in the mid-1970s. In 1984, the DoD began the Defense Environmental Restoration Program (DERP) for contaminated site assessment and remediation. Two years later, the U. S. Congress codified the DERP and directed the Secretary of Defense to carry out a concurrent program of research, development, and demonstration of innovative remediation technologies. As chronicled in the 1994 National Research Council report, “Ranking Hazardous-Waste Sites for Remedial Action,” our early estimates on the cost and suitability of existing techn- ogies for cleaning up contaminated sites were wildly optimistic. Original estimates, in 1980, projected an average Superfund cleanup cost of a mere $3.
Borne out of the current widespread interest in the pollution of water bodies, this book explores the latest research concerning the photochemical fate of organic pollutants in surface water. The main objective is to give insight into both the functioning of ecosystems and the behaviour of emerging pollutants in those ecosystems. Particular importance is dedicated to techniques that can be used in the field and in the laboratory for the detection of pollutants and of their transformation intermediates. The inclusion of photochemical processes that have not gained previous coverage will afford the reader novel insights, whilst the focus on modelling and transformation intermediates will ensure the title's relevance to academics, the chemical manufacturing industries and environmental assessment experts alike.
This book is concerned with functional nanomaterials, materials containing specific, predictable nanostructures whose chemical composition, or interfacial structure enables them to perform a specific job: to destroy, sequester, or detect some material that constitutes an environmental threat. Nanomaterials have a number of features that make them ideally suited for this job: they have a high surface area, high reactivity, easy dispersability, and rapid diffusion,to name a few. The purpose of this book is to showcase how these features can be tailored to address some of the environmental remediation and sensing/detection problems faced by mankind today. A number of leading researchers have contributed to this volume, painting a picture of diverse synthetic strategies, structures, materials, and methods. The intent of this book is to showcase the current state of environmental nanomaterials in such a way as to be useful either as a research resource, or as a graduate level textbook. We have organized this book into sections on nanoparticle-based remediation strategies, nanostructured inorganic materials (e.g. layered materials like the apatites), nanostructured organic/inorganic hybrid materials, and the use of nanomaterials to enhance the performance of sensors.
This publication comprises the presentations made at the NATO Advanced Research Workshop held in Sinaia, Romania 9 – 11 October, 2006. The contributions represent a unique cross section of issues and challenges related to contaminated site management. These range from low cost solutions to petroleum contaminated sites to advances in biological treatment methods. The publication is meant to foster links between groups facing challenges cleaning up contaminated sites.