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 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 Managing Arsenic in the Environment written by Ravi Naidu and published by CSIRO PUBLISHING. This book was released on 2006-02-07 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt: Arsenic is one of the most toxic and carcinogenic elements in the environment. This book brings together the current knowledge on arsenic contamination worldwide, reviewing the field, highlighting common themes and pointing to key areas needing future research. Contributions discuss methods for accurate identification and quantification of individual arsenic species in a range of environmental and biological matrices and give an overview of the environmental chemistry of arsenic. Next, chapters deal with the dynamics of arsenic in groundwater and aspects of arsenic in soils and plants, including plant uptake studies, effects on crop quality and yield, and the corresponding food chain and human health issues associated with these exposure pathways. These concerns are coupled with the challenge to develop efficient, cost effective risk management and remediation strategies: recent technological advances are described and assessed, including the use of adsorbants, photo-oxidation, bioremediation and electrokinetic remediation. The book concludes with eleven detailed regional perspectives of the extent and severity of arsenic contamination from around the world. It will be invaluable for arsenic researchers as well as environmental scientists and environmental chemists, toxicologists, medical scientists, and statutory authorities seeking an in-depth view of the issues surrounding this toxin.
Download or read book Influence of Redox Environments on the Mobility of Arsenic in Ground Water written by D. R. (Douglas Robert) Champ and published by [S.l.] : American Chemical Society. This book was released on 1979 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Occurrence and Mobility of Arsenic in Soils and Sediments written by Aimee Hegan and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Elevated levels of arsenic (As) in soils and water around the world are both a significant human health and environmental hazard. With increasing global water demands, there is a requirement to further the understanding of the biogeochemical cycling of As from soils and sediments. This thesis focussed on exploring the environmental controls on the occurrence and subsequent mobility of As in a range of natural environments. Arsenic was found to undergo mobilisation from both river sediments and upland peats under changing environmental conditions. The transport of As was found to be correlated with both iron (Fe) and organic carbon (OC), however temporal changes in both sediment/soil composition and movement of water through catchments have a important role in controlling the ultimate transport of As within the environment. A range of investigative methods were employed to study the occurrence and mobility of As within the river sediments of the Allier and Loire Rivers (France), including sequential extraction procedures and batch incubation studies. Arsenic was associated with the reducible phases of sediments, indicating the major role of Fe(oxy)hydroxides in the storage of As in river sediments. In addition to the presence of labile As, the rapid release of As was dependent on the initial sediment composition. Temporal changes in sediment composition may therefore play an important role in controlling the movement of As within fluvial systems. The combination of lead (Pb) and strontium (Sr) isotopic analysis with sequential extraction studies of sediments from the Loire and Allier Rivers was able to determine the relative dominance of granites and basalts within the sediments. This approach provided a first order study on which to better understand the mineral origins of the sediments. The analysis of multiple Pb isotopes was able to eliminate possible anthropogenic contribution to contamination within the sediments, confirming the importance of geogenic cycling of As within the rivers. Information on the origin of mineral formation was obtained through 87Sr/86Sr isotopic analysis, with the formation of Fe-minerals not occurring uniformly along the course of the rivers. While the Sr within the sediment phase targeting well-crystallised Fe(oxy)hydroxides was in equilibrium with the sampled river water, the formation of amorphous Fe minerals was likely occurring in waters upstream of the study sites, within the Massif Central. Total concentration profiles peat from two subcatchments within the Peak District (United Kingdom) provided evidence for both the retention and post depositional movement (PDM) of As within the solid phase, dependent on local conditions. For the first time, the partitioning of As was determined within ombrotrophic peat, and found to be in contrast to Pb, with oxidisible As (likely associated with organic matter) dominating, while Pb was found predominantly within the reducible sediment phase. High temporal resolution monitoring of the organic-rich streamwater draining the peat showed the transport of As was variable, with As found largely in the soluble form despite extensive peat erosion. The evidence for PDM, and the subsequent soluble transport of As demonstrated the importance of biogeochemical processes in releasing As from the solid phase. Once mobilised, both the ratio of Fe:OC and the form of Fe were found to be factors controlling transport of As, with the flushing of stored porewaters an important contribution to As transport from the peat. Despite OC-rich waters, the occurrence of high concentrations of Fe may dominate control of As within the aqueous phase. At relatively high (>0.2) Fe:OC ratios, the particle size distribution of As was closely correlated with that of >1um Fe, although the presence of dissolved and colloidal As was found even within these waters. Given the temporal variability of As transport within the streams, knowledge of the mixing order and ratio between Fe, OC, and As within natural waters may be required for prediction of the mobility and ultimate fate of As.
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 in Soil and Groundwater Environment written by Prosun Bhattacharya and published by Elsevier. This book was released on 2007-06-29 with total page 685 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents the recent developments in the field of arsenic in soil and groundwater. Arranged into nine sections, the text emphasizes the global occurrences of arsenic in the environment, particularly on its source, pathways, behavior, and effects it has on soils, plants, water, animals, and humans. It also covers the diverse issues of arsenic in the mining environment, arsenic emanating from hydrothermal springs, and the geochemical modeling of arsenic adsorption to oxide surfaces. Finally, the text includes different cost effective removal mechanisms of arsenic from drinking water using natural red earth, solar oxidation, and arsenic oxidation by ferrrate.Written in simple English, and few technical terms, the book is designed to create interest within the countries with occurrences of arsenic in drinking water with ·an update the current status of knowledge on the dynamics of natural arsenic from the aquifers through groundwater to food chain and efficient techniques for arsenic removal.·serve as a standard text book for graduate, postgraduate students and researchers in the field of Environmental Sciences and Hydrogeochemistry as well as researchers, environmental scientists and chemists, toxicologists, medical scientists and even for general public seeking an in-depth view of arsenic which had been classed as a carcinogen. ·bring awareness, among administrators, policy makers and company executives, on the problem and to improve the international cooperation
Download or read book In Situ Remediation of Arsenic Contaminated Sites written by Jochen Bundschuh and published by CRC Press. This book was released on 2018-10-30 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: Providing an introduction, the scientific background, case studies and future perspectives of in-situ arsenic remediation technologies for soils, soil water and groundwater at geogenic and anthropogenic contaminated sites. The case studies present in-situ technologies about natural arsenic, specifically arsenate and arsenite, but also about organic arsenic compounds. This work covers geochemical, microbiological and plant ecological solutions for arsenic remediation. It will serve as a standard textbook for (post-)graduate students and researchers in the field of Environmental Sciences and Hydrogeochemistry as well as researchers, engineers, environmental scientists and chemists, toxicologists, medical scientists and even for general public seeking an in-depth view of arsenic which had been classed as a carcinogen. This book aims to stimulate awareness among administrators, policy makers and company executives of in-situ remediation technologies at sites contamined by arsenic and to improve the international cooperation on the subject.
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 Arsenic in Geosphere and Human Diseases Arsenic 2010 written by Jiin-Shuh Jean and published by CRC Press. This book was released on 2010-04-26 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt: The congress "Arsenic in the Environment" offers an international, multi- and interdisciplinary discussion platform for arsenic research aimed at short-term solutions of problems with considerable social impact, rather than only focusing on cutting edge and breakthrough research in physical, chemical, toxicological, medical and other specific issue
Download or read book Controls on Arsenic Mobility in Contaminated Wetland and Riverbed Streams written by Nicole Elise Keon and published by . This book was released on 2002 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: (cont.) Root plaque oxidation state maps showed that both As(ll) and As(V) were retained in the plaque, suggesting that the plaque sequesters even the more mobile As(lll) species. Mass balance analysis of As revealed that the plaque was a significant sink of aqueous As. We concluded that the As retained in the Wells G & H wetland is susceptible to redox changes (particularly reduction of Fe hydroxides onto which most As is adsorbed) and displacement by competitive anions. Iron plaque formation on T. latifolia roots was shown to affect As cycling within root zone contaminated sediments by providing a substrate onto which aqueous As can adsorb.
Download or read book Arsenic Mobility in Sediments and Contamination of the Bengal Basin written by Darren Shaw and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geochemical Processes written by Horst D. Schulz and published by Wiley-VCH. This book was released on 2002-12-25 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a result of the Priority Programme 546 run by the Deutsche Forschungsgemeinschaft. It presents the various ideas, concepts and conclusions that resulted from this Programme on the subject of geochemical processes with long-term effects in anthropogenically influenced drainage and ground water.
Download or read book Microorganisms in Environmental Management written by Tulasi Satyanarayana and published by Springer Science & Business Media. This book was released on 2012-01-03 with total page 827 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microbes and their biosynthetic capabilities have been invaluable in finding solutions for several intractable problems mankind has encountered in maintaining the quality of the environment. They have, for example, been used to positive effect in human and animal health, genetic engineering, environmental protection, and municipal and industrial waste treatment. Microorganisms have enabled feasible and cost-effective responses which would have been impossible via straightforward chemical or physical engineering methods. Microbial technologies have of late been applied to a range of environmental problems, with considerable success. This survey of recent scientific progress in usefully applying microbes to both environmental management and biotechnology is informed by acknowledgement of the polluting effects on the world around us of soil erosion, the unwanted migration of sediments, chemical fertilizers and pesticides, and the improper treatment of human and animal wastes. These harmful phenomena have resulted in serious environmental and social problems around the world, problems which require us to look for solutions elsewhere than in established physical and chemical technologies. Often the answer lies in hybrid applications in which microbial methods are combined with physical and chemical ones. When we remember that these highly effective microorganisms, cultured for a variety of applications, are but a tiny fraction of those to be found in the world around us, we realize the vastness of the untapped and beneficial potential of microorganisms. At present, comprehending the diversity of hitherto uncultured microbes involves the application of metagenomics, with several novel microbial species having been discovered using culture-independent approaches. Edited by recognized leaders in the field, this penetrating assessment of our progress to date in deploying microorganisms to the advantage of environmental management and biotechnology will be widely welcomed.
Download or read book Arsenic written by Charles O. Abernathy and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Society of Environmental Geochemistry and Health (SEGH) Second International Conference on Arsenic Exposure and Health Effects was held June 12-14, 1995 in San Diego, California. The conference was at tended by 152 people who heard 41 presentations on all aspects of arsenic research. The speakers represented 14 countries. Approximately 40 of the participants and speakers were from countries other than the US. The participants represented government, academia, industry and the interested public. The sponsorship ofthe conference is a good indicationofthe wide spread interest in the subject and the meeting. The sponsors, in addition to SEGH, were the US Environmental Protection Agency (US EPA), the Agency for Toxic Substances and Disease Registry (ATSDR), the Atlantic Richfield Company (ARCO), the Electric Power Research Institute (EPRI), the American Water Works Association Research Foundation (AWWARF), Kennecott Corporation, the American Smelting and Refining Company (ASARCO), and the International Council on Metals in the Environment (ICME). The funding was split approximately equally between industry (including industrial organizations such as EPRI) and government. In addition to the many fine presentations, the meeting provided a forum for scientists from different countries to compare experiences and share information. It also provided a forum for the discussion of both scientific and policy issues between representatives of various governmental bodies (at the local, state, and federal level) and representatives of various indus trial organizations. These discussions occurred both in the formal meetings and informal settings during the meeting.
Download or read book Environmental Arsenic in a Changing World written by Yongguan Zhu and published by CRC Press. This book was released on 2019-08-23 with total page 644 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Congress "Arsenic in the Environment" offers an international, multi- and interdisciplinary discussion platform for research and innovation aimed towards a holistic solution to the problem posed by the environmental toxin arsenic, with significant societal impact. The Congress has focused on cutting edge and breakthrough research in physical, chemical, toxicological, medical, agricultural and other specific issues on arsenic across a broader environmental realm. The Biennial Congress "Arsenic in the Environment" was first organized in Mexico City (As2006) followed by As2008 in Valencia (Spain), As2010 in Tainan (Chinese Taiwan), As2012 in Cairns (Australia), As2014 in Buenos Aires (Argentina) and As2016 in Stockholm (Sweden). The 7th International Congress As2018 was held July 1-6, 2018, in Beijing, P. R. China and was entitled Environmental Arsenic in a Changing World. The Congress addressed the broader context of arsenic research aligned on the following themes: Theme 1: Arsenic Behaviour in Changing Environmental Media Theme 2: Arsenic in a Changing Agricultural Ecosystem Theme 3: Health Impacts of Environmental Arsenic Theme 4: Technologies for Arsenic Immobilization and Clean Water Blueprints Theme 5: Sustainable Mitigation and Management Arsenic in drinking water (mainly groundwater) has emerged as an issue of global health concern. During last decade, the presence of arsenic in rice, possibly also other food of plant origins, has attained increasing attention. This is particularly true in the Asian countries, where the use of high arsenic groundwater as source of irrigation water and drinking water has been flagged as severe health concern. This has been accentuated by elevating arsenic concentrations in deep groundwater recharged from shallow high arsenic groundwater, which may have further detrimental effects on public health. Notably, China has been in the forefront of research on arsenic biogeochemical cycling, health effects of arsenic, technologies for arsenic removal, and sustainable mitigation measures. The Congress has attracted professionals involved in different segments of interdisciplinary research on arsenic in an open forum, and strengthened relations between academia, research institutions, government and non-governmental agencies, industries, and civil society organizations to share an optimal ambience for exchange of knowledge.
Download or read book Geochemistry and Environmental Mineralogy of the Iron sulphur arsenic System written by Mariëtte Wolthers and published by . This book was released on 2003 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
