Download or read book The Impact of Redox Potential and Salinity on Arsenic Cycling and Mobility in Iron Oxide Systems written by Joshua Zachery Sanchez and published by . This book was released on 2022 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Additional experiments are needed to further elucidate the role of seawater in arsenate adsorption at a high pH and its effect on the arsenate-iron oxide binding complex. Also, further investigation into the role of SO42- on As and Fe cycling throughout a shifting redox potential is needed.
Download or read book Impacts of Sea Level Rise on Arsenic Mobility and Cycling in Contaminated Coastal Soils written by Joshua J. LeMonte and published by . This book was released on 2016 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: The impacts of sea level rise (SLR) on biogeochemical processes in contaminated soils and sediments along the world’s coastlines remains poorly understood. Elevated levels of the carcinogen arsenic (As), from both geogenic and anthropogenic sources, are found along many coasts, most notably in south and southeast Asia, but also in the US, particularly along the Mid-Atlantic coast. In this work, a combination of laboratory and field techniques were used to ascertain the potential impacts of impending SLR on As mobility and cycling, and the current state of As mobility in a contaminated coastal zone of Delaware, USA. Advanced biogeochemical microcosm reactors were used to simulate inundation with natural sea and river waters on two historically As-contaminated Delaware coastal soils – a wetland soil and ditch sediment – across a wide range of redox potentials while monitoring chemical variables that are known to impact As mobility. Direct As speciation of the soils after reaction at different Eh values was obtained by bulk X-ray absorption near-edge structure (XANES) spectroscopy, X-ray fluorescence (XRF) imaging, and XANES spectroscopy. Reducing conditions led to As release and partial reduction of solid-phase As for both inundation scenarios and both soils. Sulfur speciation was also determined via XANES spectroscopy and showed evidence of sulfate reduction. Prolonged reducing conditions induced by SLR will drive the release of As from historically contaminated soils, but As release may be tempered when inundated by seawater as compared to river water for some soils (e.g. ditch sediment), possibly due to reduced microbial growth in high salinity conditions or preferential sulfate reduction limiting reductive dissolution of As-bearing Fe oxides. However, other soils (e.g. wetland) may see ionic exchange driving pH shifts as a prominent factor driving As release in addition to Eh levels. To assess the contaminant mobility at one of these former industrial sites along the Christina River, we conducted quantitative comparisons of hydrologic and biogeochemical dynamics across time scales ranging from hours to months, and throughout seasonal environmental variations. The use of synchrotron-based X-ray absorption spectroscopy as a geoforensic tool suggests that As from a neighboring Superfund site is likely contributing to recent accumulation of As at the site studied. Data were collected from pressure transducers in wells, multi-level redox sensors, and porewater samplers. Results indicate that groundwater surface interaction induced a tidally controlled redox gradient. In the tidally impacted variably saturated zone, redox potential varied between oxidizing and reducing conditions depending on the water table elevation. This strong correlation indicates that a rising water table may increase contaminant mobility. Porewater samples also confirm increasing arsenic (As) concentration during the rising tide.
Download or read book Behavior of Metals in Soils written by Joan E. McLean and published by . This book was released on 1992 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamics and Bioavailability of Heavy Metals in the Rootzone written by H. Magdi Selim and published by CRC Press. This book was released on 2011-03-15 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concerns regarding heavy metal contamination in terrestrial ecosystems have prompted increasing efforts on limiting their bioavailability in the root zone. The complexity of the hydrologic system gives rise to the need for understanding the fate and transport of trace elements in the soil-water-plant environment. Dynamics and Bioavailability of Hea
Download or read book PHEs Environment and Human Health written by Claudio Bini and published by Springer. This book was released on 2014-05-14 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is dedicated to the occurrence and behaviour of PHEs in the different compartments of the environment, with special reference to soil. Current studies of PHEs in ecosystems have indicated that many industrial areas near urban agglomerates, abandoned or active mines, major road systems and ultimately also agricultural land act as sources and at the same time sinks, of PHEs and large amounts of metals are recycled or dispersed in the environment, posing severe concerns to human health. Thanks to the collaboration of numerous colleagues, the book outlines the state of art in PHEs research in several countries and is enforced with case studies and enriched with new data, not published elsewhere. The book will provide to Stakeholders (both Scientists Professionals and Public Administrators) and also to non-specialists a lot of data on the concentrations of metals in soils and the environment and the critical levels so far established, in the perspective to improve the environmental quality and the human safety.
Download or read book Microbial Oxidation of Arsenite in Anoxic Environments Impacts on Arsenic Mobility written by and published by . This book was released on 2008 with total page 674 pages. Available in PDF, EPUB and Kindle. Book excerpt: AbstractArsenic (As) contamination of groundwater and surface water is a worldwide problem. Exposure to arsenic in drinking water is an important current public health issue. Arsenic is well known for its carcinogenic and teratogenic effects. The U.S. Environmental Protection Agency (USEPA) has recently enacted a stricter drinking water standard for arsenic that lowers the maximum contaminant level (MCL) from 50 to 10 ug l-1. Localized elevated As concentrations in groundwater or surface water have been attributed to the natural release of As from the weathering of As bearing minerals. Microbial reduction of arsenate (As(V)) to arsenite (As(III)) and ferric (hydr)oxides to Fe(II) is hypothesized to be the dominant mechanisms of As mobilization in subsurface environments. If oxidizing conditions can be restored, As can be immobilized by the formation of As(V) and ferric (hydr)oxides. As(V) is more strongly adsorbed than As(III) at circumneutral conditions by common non-iron metal oxides in sediments such as those of aluminum. Ferric (hydr)oxides have strong affinity for both As(III) and As(V) in circumneutral environments. Oxygen can be introduced into the anaerobic zone by injection of gaseous O2 to promote oxidation reactions of As(III) and Fe(II), but O2 is poorly soluble and chemically reactive and thus difficult to distribute in the subsurface. Nitrate or chlorate can be considered as alternative oxidants with advantages over elemental oxygen due to their high aqueous solubility and lower chemical reactivity which together enable them to be better dispersed in the saturated subsurface. The objective of this study is to evaluate the importance of anoxic oxidation of As(III) to As(V) by anaerobic microorganisms such as chemolithotrophic denitrifying bacteria and chlorate respiring bacteria in the biogeochemical cycle of arsenic. This study also investigated a arsenic potential bioremediation strategy based on injecting nitrate or chlorate into contaminated groundwater and surface water under anaerobic conditions. In this study, denitrification or chlorate reduction linked to the oxidation of As(III) to As(V) was shown to be a widespread microbial activity in anaerobic sludge and sediment samples that were not previously exposed to arsenic contamination. The biological oxidation of As(III) utilizing nitrate or chlorate as sole electron acceptor was feasible and stable over prolonged periods of operation in continuous-flow anaerobic bioreactors. Evidence for the complete denitrification was demonstrated by direct measurement of N2 formation dependent on As(III) addition. Also complete chlorate reduction to chloride was attributable to the oxidation of As(III). A 16S rRNA gene clone library characterization of enrichment cultures indicated that the predominant phylotypes responsible for As(III) oxidation linked to denitrification were from the genus Azoarcus and the family Comamonadaceae. A bioremediation strategy was explored that is based on injecting nitrate to support the microbial oxidation of Fe(II) and As(III) in the subsurface as a means to immobilize arsenic. Two models were utilized to illustrate the mechanisms of As removal. 1)Sediment columns packed with activated alumina were utilized to demonstrate the role of nitrate in supporting microbial As(III) oxidation and arsenic mobility in anoxic sediments containing mostly non-iron oxides;2)Sand-packed columns were used to simulate natural anaerobic groundwater and sediment systems with co-occurring As(III) and Fe(II) in the presence or absence of nitrate. Microbial oxidation by denitrifying microorganisms lead to the formation of ferric (hydroxides) which adsorbed As(V) formed from As(III)-oxidation. The studies presented here demonstrate that anoxic microbial oxidation of As(III) and Fe(II) linked to denitrification significantly enhance the immobilization of As in the anaerobic subsurface environments.
Download or read book The Metabolism of Arsenite written by Joanne M. Santini and published by CRC Press. This book was released on 2018-10-03 with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt: Up to 200 million people in 70 countries are at risk from drinking water contaminated with arsenic, which is a major cause of chronic debilitating illnesses and fatal cancers. Until recently little was known about the mobility of arsenic, and how redox transformations determined its movement into or out of water supplies. Although human activities contribute to the release of arsenic from minerals, it is now clear that bacteria are responsible for most of the redox transformation of arsenic in the environment. Bacterial oxidation of arsenite (to the less mobile arsenate) has been known since 1918, but it was not until 2000 that a bacterium was shown to gain energy from this process. Since then a wide range of arsenite-oxidizing bacteria have been isolated, including aerobes and anaerobes; heterotrophs and autotrophs; thermophiles, mesophiles and psychrophiles. This book reviews recent advances in the study of such bacteria. After a section on background—geology and health issues—the main body of the book concerns the cellular machinery of arsenite oxidation. It concludes by examining possible applications. Topics treated are: The geology and cycling of arsenic Arsenic and disease Arsenite oxidation: physiology, enzymes, genes, and gene regulation. Community genomics and functioning, and the evolution of arsenite oxidation Microbial arsenite oxidation in bioremediation Biosensors for arsenic in drinking water and industrial effluents
Download or read book Environmental Geochemistry written by B. Sherwood Lollar and published by Elsevier. This book was released on 2005-05-21 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Treatise on Geochemistry is the first work providing a comprehensive, integrated summary of the present state of geochemistry. It deals with all the major subjects in the field, ranging from the chemistry of the solar system to environmental geochemistry. The Treatise on Geochemistry has drawn on the expertise of outstanding scientists throughout the world, creating the reference work in geochemistry for the next decade. Each volume consists of fifteen to twenty-five chapters written by recognized authorities in their fields, and chosen by the Volume Editors in consultation with the Executive Editors. Particular emphasis has been placed on integrating the subject matter of the individual chapters and volumes. Elsevier also offers the Treatise on Geochemistry in electronic format via the online platform ScienceDirect, the most comprehensive database of academic research on the Internet today, enhanced by a suite of sophisticated linking, searching and retrieval tools.
Download or read book Arsenic in Ground Water written by Alan H. Welch and published by Springer Science & Business Media. This book was released on 2007-05-08 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interest in arsenic in ground water has greatly increased in the past decade because of the increased awareness of human health effects and the costs of avoidance or treatment of ground water supplies used for consumption. The goal of this book is to provide a description of the basic processes that affect arsenic occurrence and transport by providing sufficient background information on arsenic geochemistry and descriptions of hi- arsenic ground water, both affected and unaffected by human activity. An understanding of thermodynamics, adsorption, and the speciation of arsenic in solid phases, which are described in first three chapters, is needed to predict the fate of arsenic in ground water systems. Large-scale and deep movement of ground water can and has redistributed arsenic in the near surface environment, as described in the next two chapters. These large-scale systems can affect large volumes of both ground water and surface water, such as in the Yellowstone system, and can produce mineralised zones that subsequently release arsenic to ground water supplies. Regional identification of high-arsenic ground water and its consumption as described in the next three chapters clearly demonstrates a need for increased wat- quality monitoring, particularly in south and southeast Asia. Chapters 9-11 provide examples of high arsenic ground water associated with sulfide mineral oxidation and alkaline conditions. Finally, smaller scale studies of the effects of human activities that have produced high-arsenic ground water and methods for attenuation of ground water are presented.
Download or read book Arsenic Mobility in Suboxic Environments written by and published by . This book was released on 2009 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mechanisms controlling arsenic mobility, including competition with oxyanion ortho-phosphate, in the subsurface and in laboratory controlled experiments were investigated. Additionally, the solubility and meta-stability of GR as a sorbing surface for arsenic in sub-oxic environments was examined. A systems approach was employed to: 1) investigate a model system constrained by thermodynamic constants and a well defined field site, 2) examine a synthetic system to elucidated the effects of co-precipitating oxyanions of arsenic and phosphate with GR, a scenario expected as an environment transitions from oxic to suboxic conditions, and 3) to study the abiotic conditions where GR formation is favorable in suboxic conditions. A systems approach, defined here as the method of investigating a problem by looking at individual but inter-dependent components in the broader context of a larger interdisciplinary environment, was employed to investigate GR in natural and laboratory controlled settings. This research has investigated the mineralogical response, and subsequent surface complexation reactions, to a redox change from oxic to sub oxic conditions. A redox gradient is commonly encountered in nature, observed in wetlands and from flooding sediments. These findings can be applied to a contaminant management plan, and may be important when considering the anticipated precipitation pattern changes due to global climate change. The overall goal of this study was to characterize mineralogical structural changes and solubilities of the solid phase iron sorbate host and the dissolved constituents (incl. nutrients and contaminants) in suboxic environments. Generally, suboxic environments are found in wetlands and submerged soils. Because wetlands accumulate dissolved ions from a vast watershed, a geochemical response to a hydrologic perturbation will likely affect contaminant and nutrient cycling in the region, and should be included in any management response. Iron is one of the most abundant elements in soils and the most abundant redox active element in natural systems, is generally dissolved as a reduced species (FeII) and insoluble as an oxidized species (FeIII). Therefore, iron transitions are principally controlled by the availability of oxygen. The result is a variety of iron oxide and hydroxide mineral phases that are stable and meta-stable under different soil PO2 conditions. Due to the transient variability between the aqueous Fe(II) and solid phase Fe(III) redox states, iron plays a major role in controlling the nutrient and contaminant cycling in subsurface environment. This research has investigated green rusts that may form at the redox boundary between fully oxidized and sub oxic sediments (Root et al. 2007, 2009). A primary goal of this research was to increase the scientific knowledge base concerning arsenic clean up and remediation, removal from the drinking water supply, and sequestration in the solid phase thereby isolating arsenic from uptake into the biota.
Download or read book Selected Water Resources Abstracts written by and published by . This book was released on 1986 with total page 880 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Microbially Mediated Iron and Sulfur Cycling on Arsenic Mobility written by Samantha L. Saalfield and published by . This book was released on 2009 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Arsenate and Arsenite Retention and Release in Oxide and Sulfide Dominated Systems written by Richard H. Loeppert and published by . This book was released on 1997 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Arsenic Rice written by Andrew A. Meharg and published by Springer Science & Business Media. This book was released on 2012-03-01 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rice is the staple food for half of the world’s population. Consumption of rice is the major exposure route globally to the class one, non-threshold carcinogen inorganic arsenic. This book explains the sources of arsenic to paddy soils and the biogeochemical processes and plant physiological attributes of paddy soil-rice ecosystems that lead to high concentrations of arsenic in rice grain. It presents the global pattern of arsenic concentration and speciation in rice, discusses human exposures to inorganic arsenic from rice and the resulting health risks. It also highlights particular populations that have the highest rice consumptions, which include Southern and South East Asians, weaning babies, gluten intolerance sufferers and those consuming rice milk. The book also presents the information of arsenic concentration and speciation in other major crops and outlines approaches for lowering arsenic in rice grain and in the human diet through agronomic management.
Download or read book Treatise on Geochemistry Environmental geochemistry written by Heinrich D. Holland and published by . This book was released on 2004 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Redox written by J. Schüring and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: Few processes are as important for environmental geochemistry as the interplay between the oxidation and reduction of dissolved and solid species. The knowledge of the redox conditions is most important to predict the geochemical behaviour of a great number of components, the mobilities of which are directly or indirectly controlled by redox processes. The understanding of the chemical mechanisms responsible for the establishment of measurable potentials is the major key for the evaluation and sensitive interpretation of data. This book is suitable for advanced undergraduates as well as for all scientists dealing with the measurement and interpretation of redox conditions in the natural environment.
Download or read book Heavy Metals in Soils written by Brian J. Alloway and published by Springer Science & Business Media. This book was released on 2012-07-18 with total page 615 pages. Available in PDF, EPUB and Kindle. Book excerpt: This third edition of the book has been completely re-written, providing a wider scope and enhanced coverage. It covers the general principles of the natural occurrence, pollution sources, chemical analysis, soil chemical behaviour and soil-plant-animal relationships of heavy metals and metalloids, followed by a detailed coverage of 21 individual elements, including: antimony, arsenic, barium, cadmium, chromium, cobalt, copper, gold, lead, manganese, mercury, molybdenum, nickel, selenium, silver, thallium, tin, tungsten, uranium, vanadium and zinc. The book is highly relevant for those involved in environmental science, soil science, geochemistry, agronomy, environmental health, and environmental engineering, including specialists responsible for the management and clean-up of contaminated land.
