Heterogeneous Interactions of Arsenic in Aquatic Systems

Holm, Thomas R.; Anderson, Marc A.; Iverson, Dennis G.; Stanforth, Robert

doi:10.1021/bk-1979-0093.ch031

Cited by 24 publications

(7 citation statements)

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“…The conversion of As (III) to As (V) by suspended and bottom sediments is thus deemed to be of significance in maintaining the ecological balance in freshwater environments. In addition, As (V) is more strongly sorbed by sediment components than is As (III) (Gulens et a 1979;Holm et al 1979). Therefore, the bioavailability and toxicity of the adsorbed As may decrease upon oxidation of As (III) to As (V).…”

Section: Resultsmentioning

confidence: 99%

Dynamics and mechanisms of arsenite oxidation by freshwater lake sediments

Huang

Oscarson

Liaw³

et al. 1982

Hydrobiologia

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There has been increasing concern over As in freshwater environments from sources such as arsenical pesticides, smelters, coal-fired power plants, and erosion caused by intensive land use. Arsenic in the reduced state, As (III) (arsenite), is much more toxic, more soluble and mobile, than when in the oxidized state, As (V) (arsenate). This paper summarizes the dynamics and mechanisms involved in the oxidation of As (III) to As (V) by freshwater lake sediments. Sediments from selected freshwater lakes in southern Saskatchewan oxidize As (III) to As (V) predominantly through an abiotic process. Solution analysis of As (III) and As (V) by colorimetry, and examination of the oxidation state of surface-sorbed As species by X-ray photoelectron spectroscopy, indicate that Mn present in the sediment is the primary electron acceptor in the oxidation of As (III). The transformation of As (III) to As (V) by carbonate and silicate minerals, common in sediments, is not evident. The heat of activation, AHa, for the depletion (oxidation plus sorption) of As (III) by the sediments, varies from 3.3 to 8.5 kcal mole-1 , indicating that the process is predominantly diffusion-controlled. The Mn present in a series of particle size fractions (<2->20 gm) of the sediments may potentially detoxify As (III) in aquatic systems, by converting it to As (V).

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Section: Resultsmentioning

confidence: 99%

Dynamics and mechanisms of arsenite oxidation by freshwater lake sediments

Huang

Oscarson

Liaw³

et al. 1982

Hydrobiologia

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“…However, Holm et al (1979) found adsorption of arsenite on river sediments was linearly dependent on concentration while arsenate adsorption followed a Langmuir isotherm. Initial arsenic levels were 10 −5 − 10 −4 M and pH was not mentioned.…”

Section: Review Of Arsenic Adsorption Literaturementioning

confidence: 94%

Electrochemical arsenic remediation for rural Bangladesh

Addy¹

2008

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Professor Ashok Gadgil, Co-Chair Professor Robert Jacobsen, Co-Chair Arsenic in drinking water is a major public health problem threatening the lives of over 140 million people worldwide. In Bangladesh alone, up to 57 million people drink arsenic-laden water from shallow wells. ElectroChemical Arsenic Remediation (ECAR) overcomes many of the obstacles that plague current technologies and can be used affordably and on a small-scale, allowing for rapid dissemination into Bangladesh to address this arsenic crisis.In this work, ECAR was shown to effectively reduce 550 -580 µg/L arsenic (including both As [III] and As[V] in a 1:1 ratio) to below the WHO recommended maximum limit of 10 µg/L in synthetic Bangladesh groundwater containing relevant concentrations of competitive ions such as phosphate, silicate, and bicarbonate. Arsenic removal capacity was found to be approximately constant within certain ranges of current density, but was found to change substantially between ranges. In order of decreasing arsenic 2 removal capacity, the pattern was: 0.02 mA/cm 2 > 0.07 mA/cm 2 > 0.30 -1.1 mA/cm 2 > 5.0 -100 mA/cm 2 . Current processing time was found to effect arsenic removal capacity independent of either charge density or current density. Electrode polarization studies showed no passivation of the electrode in the tested range (up to current density 10 mA/cm 2 ) and ruled out oxygen evolution as the cause of decreasing removal capacity with current density. Simple settling and decantation required approximately 3 days to achieve arsenic removal comparable to filtration with a 0.1 µm membrane.X-ray Absorption Spectroscopy (XAS) showed that (1) there is no significant difference in the arsenic removal mechanism of ECAR during operation at different current densities and (2) the arsenic removal mechanism in ECAR is consistent with arsenate adsorption onto a homogenous Fe(III)oxyhydroxide similar in structure to 2-line ferrihydrite.ECAR effectively reduced high arsenic concentrations (100 -500 µg/L) in real Bangladesh tube well water collected from three regions to below the WHO limit of 10 µg/L. Prototype fabrication and field testing are currently underway.

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“…While different components of sediments participate in the immobilization of arsenic species, the major role appears to be played by hydrous oxides of such metals as iron, aluminum, and manganese as well as surface sites on clay particles containing these elements (9,17). Of particular relevance to the discussion is the fact that the relative efficacy of As binding to these components is a function of pH, redox potential, and species of arsenic (18)(19)(20).…”

Section: Potential Interrelationships Of As In Drinking Water Systemsmentioning

confidence: 99%

Potential impact of acid precipitation on arsenic and selenium.

Mushak¹

1985

Environ Health Perspect

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The potential impact of acidic precipitation on the environmental mobility of the metalloids arsenic (As) and selenium (Se) has not been given much attention and is poorly understood. As with other elements, the interest here is the potential effect of environmental acidification on environmental behavior in ways that are relevant to human exposure to these metalloids. Available information on acid precipitation and the environmental behavior of these metalloids do, however, permit some preliminary conclusions to be drawn.Both As and Se appear to be mobilized from household plumbing into tap water by the corrosive action of soft, mildly acidic water, while surface water catchment systems in areas impacted by acidic deposition may contain elevated soluble As levels.Acidification of aquatic ecosystems that are drinking water sources may pose the prospect of enhanced release of As from sediment to water as well as reduction in water levels of Se. Acidification of ground waters, where As appears to be especially mobile, is of particular concern in this regard.The potential impact of acidic deposition on As and Se in soils cannot readily be assessed with respect to human exposure, but it would appear that the behavior of these metalloids in poorly buffered, poorly immobilizing soils, e.g., sandy soils of low metal hydrous oxide content, would be most affected. The effect is opposite for the two elements; lowered pH would appear to enhance As mobility and to reduce Se availability.Altered acidity of both soil and aquatic systems poses a risk for altered biotransformation processes involving both As and Se, thereby affecting the relative amounts of different chemical forms varying in their toxicity to humans as well as influencing biogeochemical cycling.

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Heterogeneous Interactions of Arsenic in Aquatic Systems

Cited by 24 publications

References 0 publications

Dynamics and mechanisms of arsenite oxidation by freshwater lake sediments

Dynamics and mechanisms of arsenite oxidation by freshwater lake sediments

Electrochemical arsenic remediation for rural Bangladesh

Potential impact of acid precipitation on arsenic and selenium.

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