Showing papers on "Arsenic published in 2010"
TL;DR: The magnetite-graphene hybrids show a high binding capacity for As(III) and As(V), whose presence in the drinking water in wide areas of South Asia has been a huge problem.
Abstract: Magnetite−graphene hybrids have been synthesized via a chemical reaction with a magnetite particle size of ∼10 nm. The composites are superparamagnetic at room temperature and can be separated by an external magnetic field. As compared to bare magnetite particles, the hybrids show a high binding capacity for As(III) and As(V), whose presence in the drinking water in wide areas of South Asia has been a huge problem. Their high binding capacity is due to the increased adsorption sites in the M−RGO composite which occurs by reducing the aggregation of bare magnetite. Since the composites show near complete (over 99.9%) arsenic removal within 1 ppb, they are practically usable for arsenic separation from water.
1,806 citations
TL;DR: A range of mitigation methods, from agronomic measures and plant breeding to genetic modification, may be employed to reduce As uptake by food crops.
Abstract: Arsenic (As) is an environmental and food chain contaminant. Excessive accumulation of As, particularly inorganic arsenic (As(i)), in rice (Oryza sativa) poses a potential health risk to populations with high rice consumption. Rice is efficient at As accumulation owing to flooded paddy cultivation that leads to arsenite mobilization, and the inadvertent yet efficient uptake of arsenite through the silicon transport pathway. Iron, phosphorus, sulfur, and silicon interact strongly with As during its route from soil to plants. Plants take up arsenate through the phosphate transporters, and arsenite and undissociated methylated As species through the nodulin 26-like intrinsic (NIP) aquaporin channels. Arsenate is readily reduced to arsenite in planta, which is detoxified by complexation with thiol-rich peptides such as phytochelatins and/or vacuolar sequestration. A range of mitigation methods, from agronomic measures and plant breeding to genetic modification, may be employed to reduce As uptake by food crops.
1,025 citations
TL;DR: Chronic arsenic exposure through drinking water was associated with an increase in the mortality rate and follow-up data from this cohort will be used to assess the long-term effects of arsenic exposure and how they might be affected by changes in exposure.
637 citations
TL;DR: It is demonstrated that in the absence of two ABCC-type transporters, At ABCC1 and AtABCC2, Arabidopsis thaliana is extremely sensitive to arsenic and arsenic-based herbicides and engineering of plants suited either for phytoremediation or reduced accumulation of arsenic in edible organs is possible.
Abstract: Arsenic is an extremely toxic metalloid causing serious health problems. In Southeast Asia, aquifers providing drinking and agricultural water for tens of millions of people are contaminated with arsenic. To reduce nutritional arsenic intake through the consumption of contaminated plants, identification of the mechanisms for arsenic accumulation and detoxification in plants is a prerequisite. Phytochelatins (PCs) are glutathione-derived peptides that chelate heavy metals and metalloids such as arsenic, thereby functioning as the first step in their detoxification. Plant vacuoles act as final detoxification stores for heavy metals and arsenic. The essential PC–metal(loid) transporters that sequester toxic metal(loid)s in plant vacuoles have long been sought but remain unidentified in plants. Here we show that in the absence of two ABCC-type transporters, AtABCC1 and AtABCC2, Arabidopsis thaliana is extremely sensitive to arsenic and arsenic-based herbicides. Heterologous expression of these ABCC transporters in phytochelatin-producing Saccharomyces cerevisiae enhanced arsenic tolerance and accumulation. Furthermore, membrane vesicles isolated from these yeasts exhibited a pronounced arsenite [As(III)]–PC2 transport activity. Vacuoles isolated from atabcc1 atabcc2 double knockout plants exhibited a very low residual As(III)–PC2 transport activity, and interestingly, less PC was produced in mutant plants when exposed to arsenic. Overexpression of AtPCS1 and AtABCC1 resulted in plants exhibiting increased arsenic tolerance. Our findings demonstrate that AtABCC1 and AtABCC2 are the long-sought and major vacuolar PC transporters. Modulation of vacuolar PC transporters in other plants may allow engineering of plants suited either for phytoremediation or reduced accumulation of arsenic in edible organs.
531 citations
TL;DR: In this article, the adsorption of arsenic on magnetic nanomaterials was studied as a function of pH, initial arsenic concentration, contact time and coexisting anions.
476 citations
TL;DR: Magnetite-maghemite nanoparticles can readily adsorb arsenic and chromium in an acidic pH range, and it is anticipated that an optimum design with magnetite- maghemites nanoparticles may achieve high arsenic uptake in field applications.
416 citations
TL;DR: In the simultaneous presence of Fe(III) oxyhydroxides and Fe(II), as commonly observed in environments inhabited by iron-reducing microorganisms, As( III) oxidation can occur, which potentially explains the presence of As(V) in reduced groundwater aquifers.
Abstract: The redox state and speciation of the metalloid arsenic (As) determine its environmental fate and toxicity. Knowledge about biogeochemical processes influencing arsenic redox state is therefore necessary to understand and predict its environmental behavior. Here we quantified arsenic redox changes by pH-neutral goethite [alpha-Fe(III)OOH] mineral suspensions amended with Fe(II) using wet-chemical and synchrotron X-ray absorption (XANES) analysis. Goethite itself did not oxidize As(III) and, in contrast to thermodynamic predictions, Fe(II)-goethite systems did not reduce As(V). However, we observed rapid oxidation of As(III) to As(V) in Fe(II)-goethite systems. Mossbauer spectroscopy showed initial formation of (57)Fe-goethite after (57)Fe(II) addition plus a so far unidentified additional Fe(II) phase. No other Fe(III) phase could be detected by Mossbauer, EXAFS, SEM, XRD, or HR-TEM. This suggests that reactive Fe(III) species form as an intermediate Fe(III) phase upon Fe(II) addition and electron transfer into bulk goethite but before crystallization of the newly formed Fe(III) as goethite. In summary this study indicates that in the simultaneous presence of Fe(III) oxyhydroxides and Fe(II), as commonly observed in environments inhabited by iron-reducing microorganisms, As(III) oxidation can occur. This potentially explains the presence of As(V) in reduced groundwater aquifers.
280 citations
TL;DR: Results show that rice is more efficient than wheat or barley in arsenite uptake and translocation, probably through the highly efficient pathway for silicon.
Abstract: Rice is efficient at arsenic (As) accumulation, thus posing a potential health risk to humans and animals. Arsenic bioavailability in submerged paddy soil is enhanced due to mobilisation of arsenite, but rice may also have an inherently greater ability to take up and translocate arsenite than other cereal crops. To test this hypothesis, rice, wheat and barley were exposed to 5 µM arsenate or arsenite for 24 h. Arsenic uptake and distribution, and As speciation in the xylem sap and nutrient solution were determined. Regardless of the As form supplied to plants, rice accumulated more As in the shoots than wheat or barley. Arsenite uptake by rice was double of that by wheat or barley, whereas arsenate uptake was similar between rice and wheat and approximately a third smaller in barley. The efficiency of As translocation from roots to shoots was greater when plants were supplied with arsenite than with arsenate, and in both treatments rice showed the highest translocation efficiency. Arsenite was the main species of As (86–97%) in the xylem sap from arsenite-treated plants of all three species. In the arsenate-treated plants, 84%, 45% and 63% of As in the xylem sap of rice, wheat and barley, respectively, was arsenite. Arsenite efflux to the external medium was also observed in all three plant species exposed to arsenate. The results show that rice is more efficient than wheat or barley in arsenite uptake and translocation, probably through the highly efficient pathway for silicon.
279 citations
TL;DR: In this paper, a Ce-Ti hybrid oxide adsorbent with high sorption capacities for As(V) and As(III) was successfully prepared using a two-step reaction.
254 citations
TL;DR: It is shown that ACR3 localizes to the vacuolar membrane in gametophytes, indicating that it likely effluxes arsenite into the vacUole for sequestration and may explain arsenic tolerance in this unusual group of ferns while precluding the same trait in angiosperms.
Abstract: The fern Pteris vittata tolerates and hyperaccumulates exceptionally high levels of the toxic metalloid arsenic, and this trait appears unique to the Pteridaceae. Once taken up by the root, arsenate is reduced to arsenite as it is transported to the lamina of the frond, where it is stored in cells as free arsenite. Here, we describe the isolation and characterization of two P. vittata genes, ACR3 and ACR3;1, which encode proteins similar to the ACR3 arsenite effluxer of yeast. Pv ACR3 is able to rescue the arsenic-sensitive phenotypes of yeast deficient for ACR3. ACR3 transcripts are upregulated by arsenic in sporophyte roots and gametophytes, tissues that directly contact soil, whereas ACR3;1 expression is unaffected by arsenic. Knocking down the expression of ACR3, but not ACR3;1, in the gametophyte results in an arsenite-sensitive phenotype, indicating that ACR3 plays a necessary role in arsenic tolerance in the gametophyte. We show that ACR3 localizes to the vacuolar membrane in gametophytes, indicating that it likely effluxes arsenite into the vacuole for sequestration. Whereas single-copy ACR3 genes are present in moss, lycophytes, other ferns, and gymnosperms, none are present in angiosperms. The duplication of ACR3 in P. vittata and the loss of ACR3 in angiosperms may explain arsenic tolerance in this unusual group of ferns while precluding the same trait in angiosperms.
242 citations
TL;DR: The presence of arsenic in marine samples was first reported over 100 years ago, and shortly thereafter it was shown that common seafood such as fish, crustaceans, and mol- luscs contained arsenic at exceedingly high concentrations as discussed by the authors.
Abstract: The presence of arsenic in marine samples was first reported over 100 years ago, and shortly thereafter it was shown that common seafood such as fish, crustaceans, and mol- luscs contained arsenic at exceedingly high concentrations. It was noted at the time that this seafood arsenic was probably present as an organically bound species because the concen- trations were so high that if the arsenic had been present as an inorganic species it would cer- tainly have been toxic to the humans consuming seafood. Investigations in the late 1970s identified the major form of seafood arsenic as arsenobetaine ((CH 3 ) 3 As + CH 2 COO - ), a harmless organoarsenic compound which, following ingestion by humans, is rapidly excreted in the urine. Since that work, however, over 50 additional arsenic species have been identi- fied in marine organisms, including many important food products. For most of these arsenic compounds, the human toxicology remains unknown. The current status of arsenic in seafood will be discussed in terms of the possible origin of these compounds and the implications of their presence in our foods.
TL;DR: Among the parameters affecting the As rejection, feed concentration plays a key role for the production of a permeate stream respecting the limits imposed by WHO.
TL;DR: In this paper, the authors used the Box-Behnken statistical experiment design (BBD) and response surface methodology (RSM) to investigate the effects of major operating variables.
TL;DR: In this article, the level of severity of arsenic contamination, concentrations of arsenic in irrigation water, soil, rice, wheat, common vegetables, and pulses, intensively cultivated and consumed by the people of highly arsenic affected Nadia district, West Bengal, India, were investigated.
Abstract: Ganga-Meghna-Bramhaputra basin is one of the major arsenic-contaminated hotspot in the world. To assess the level of severity of arsenic contamination, concentrations of arsenic in irrigation water, soil, rice, wheat, common vegetables, and pulses, intensively cultivated and consumed by the people of highly arsenic affected Nadia district, West Bengal, India, were investigated. Results revealed that the arsenic-contaminated irrigation water (0.318–0.643 mg l-1) and soil (5.70–9.71 mg kg-1) considerably influenced in the accumulation of arsenic in rice, pulses, and vegetables in the study area. Arsenic concentrations of irrigation water samples were many folds higher than the WHO recommended permissible limit for drinking water (0.01 mg l-1) and FAO permissible limit for irrigation water (0.10 mg l-1). But, the levels of arsenic in soil were lower than the reported global average of 10.0 mg kg-1 and was much below the EU recommended maximum acceptable limit for agricultural soil (20.0 mg kg-1). The total arsenic concentrations in the studied samples ranged from <0.0003 to 1.02 mg kg-1. The highest and lowest mean arsenic concentrations (milligrams per kilogram) were found in potato (0.654) and in turmeric (0.003), respectively. Higher mean arsenic concentrations (milligrams per kilogram) were observed in Boro rice grain (0.451), arum (0.407), amaranth (0.372), radish (0.344), Aman rice grain (0.334), lady's finger (0.301), cauliflower (0.293), and Brinjal (0.279). Apart from a few potato samples, arsenic concentrations in the studied crop samples, including rice grain samples were found not to exceed the food hygiene concentration limit (1.0 mg kg-1). Thus, the present study reveals that rice, wheat, vegetables, and pulses grown in the study area are safe for consumption, for now. But, the arsenic accumulation in the crops should be monitored periodically as the level of arsenic toxicity in the study area is increasing day by day.
TL;DR: Efforts on gene expression profiling, deep transcriptome sequencing, high throughput metabolomics and phenotyping of contrasting arsenic accumulating lines need to be increased to develop strategies for design of safer rice varieties.
Abstract: Arsenic is commonly present in subsoil and is a carcinogen in humans. Rice takes up arsenic and it accumulates in different plant parts, including grains, at levels several-fold higher than the soil. In high arsenic regions, rice can contribute substantially to arsenic intake by the human population. Arsenic in rice grains is present in the carcinogenic inorganic or the relatively safer organic (methylated) form. A wide variation is noticed in different rice genotypes with respect to the proportion of arsenic in these forms in grains. Mechanisms involved in arsenic uptake, efflux from roots, loading into xylem, transport, partitioning, arsenate reduction, arsenic sequestration in vacuoles, volatilization from leaves, accumulation in grains etc. are poorly understood. Selection of cultivars accumulating low inorganic arsenic is an important trait to be used by breeders to develop rice varieties safer for cultivation in arsenic-contaminated regions. Systematic efforts have not been made to screen rice genotypes for mining the genes involved in arsenic uptake, transport and accumulation in grains. Identification of rice germplasm with varying arsenic uptake and partitioning, and development of mapping populations with contrasting grain arsenic, are required for association studies and QTL mapping for accelerating rice improvement. Efforts on gene expression profiling, deep transcriptome sequencing, high throughput metabolomics and phenotyping of contrasting arsenic accumulating lines need to be increased to develop strategies for design of safer rice varieties. Network research projects need to be developed along these approaches to accelerate the development of crop varieties safer for farming in arsenic-contaminated environments.
TL;DR: Natural scoria studied in this work is an efficient sorbent for concurrent removal of divalent heavy metals and arsenic from aqueous solutions by scoria.
TL;DR: Bulk X-ray absorption near-edge structure analysis shows arsenic in these near-surface samples is mainly in the pentavalent form, indicating that most of the arsenopyrite originally present in the tailings and soils has been oxidized during weathering reactions.
Abstract: Bioaccessibility tests and mineralogical analyses were performed on arsenic-contaminated tailings and soils from gold mine districts of Nova Scotia, Canada, to examine the links between soil composition, mineralogy, and arsenic bioaccessibility. Arsenic bioaccessibility ranges from 0.1% to 49%. A weak correlation was observed between total and bioaccessible arsenic concentrations, and the arsenic bioaccessibility was not correlated with other elements. Bulk X-ray absorption near-edge structure analysis shows arsenic in these near-surface samples is mainly in the pentavalent form, indicating that most of the arsenopyrite (As1−) originally present in the tailings and soils has been oxidized during weathering reactions. Detailed mineralogical analyses of individual samples have identified up to seven arsenic species, the relative proportions of which appear to affect arsenic bioaccessibility. The highest arsenic bioaccessibility (up to 49%) is associated with the presence of calcium−iron arsenate. Samples co...
TL;DR: The aim of the present work is to investigate the efficiency of the oxidation of As(III) by means of four conventional oxidants (chlorine dioxide, sodium hypochlorite, potassium permanganate and monochloramine) with different test conditions: different type of water (demineralised and real water), different pH values and different doses of chemicals.
TL;DR: The amount of total As(III) formed during soil reduction was linearly correlated to the amount oftotal Fe(II) formed, indicating that the rate of As(V) reduction was controlled by the rates of microbial Fe(III] (hydr)oxide reduction.
Abstract: Arsenic (As) in soils and sediments is commonly mobilized when anoxic conditions promote microbial iron (Fe) and As reduction. Recent laboratory studies and field observations have suggested a decoupling between Fe and As reduction and release, but the links between these processes are still not well understood. In microcosm experiments, we monitored the formation of Fe(II) and As(III) in the porewater and in the soil solid-phase during flooding of a contaminated floodplain soil at temperatures of 23, 14, and 5 °C. At all temperatures, flooding induced the development of anoxic conditions and caused increasing concentrations of dissolved Fe(II) and As(III). Decreasing the temperature from 23 to 14 and 5 °C strongly slowed down soil reduction and Fe and As release. Speciation of As in the soil solid-phase by X-ray absorption spectroscopy (XAS) and extraction of the Fe(II) that has formed by reductive Fe(III) (hydr)oxide dissolution revealed that less than 3.9% of all As(III) and less than 3.2% of all Fe(II...
TL;DR: X-ray absorption spectroscopy and X-ray diffraction data show that Mn(II) sorption on a poorly crystalline hexagonal birnessite (δ-MnO₂) is important in passivation early during reaction with As(III).
Abstract: Arsenite (AsIII) oxidation by manganese oxides (Mn-oxides) serves to detoxify and, under many conditions, immobilize arsenic (As) by forming arsenate (AsV). AsIII oxidation by MnIV-oxides can be qu...
TL;DR: Fe-GACs synthesized in this study exhibited higher affinity for arsenate as compared with references in literature and shows great potential for real implementations.
TL;DR: It is demonstrated that the metabolism of anaerobic nitrate-reducing and phototrophic Fe(II)-oxidizing bacteria is not significantly affected by arsenate concentrations of up to 500 muM (37.5 mg/L), and cell metabolism was significantly impaired only at the highest arsenite concentration (500 muM) for one of the Fe(III)oxidizers.
Abstract: More than 100 million individuals worldwide are exposed to arsenic-contaminated water, making the investigation of arsenic mobility in aquatic systems of utmost importance. Iron (hydr)oxides play a key role in preventing arsenic release in aquifers and soils due to their strong arsenic sorption and are even used to remove arsenic in water treatment. Neutrophilic Fe(II)-oxidizing bacteria produce Fe(III) minerals and therefore have the potential to affect arsenic mobility. In the present study, we demonstrate that the metabolism of anaerobic nitratereducing and phototrophic Fe(II)-oxidizing bacteria is not significantly affected by arsenate concentrations of up to 500 µM (37.5 mg/L). Even in the presence of the more toxic arsenic species, arsenite, cell metabolism was significantly impaired only at the highest arsenite concentration (500 µM) for one of the Fe(II)-oxidizers. All Fe(II)-oxidizing bacteria tested effectively immobilized arsenic during Fe(II) oxidation (>96%), lowering the remaining dissolved arsenic concentrations to values close to or even lower than the current drinking water limit of 10 µg/L. Since the minerals formed by these bacteria includedhighlycrystallineFe(III)mineralsthatarehardlyreducible byFe(III)-reducingbacteria,stimulationofarsenicimmobilization by Fe(II)-oxidizing bacteria can potentially support water treatmentsystemsorevenbeappliedasaneffectiveremediation strategy.
TL;DR: In this paper, the role of Fe(II) in the oxidation of As(III) at the surface of magnetite and ferrihydrite under oxygenated conditions was investigated.
Abstract: To reduce the adverse effects of arsenic on humans, various technologies are used to remove arsenic from groundwater, most relying on As adsorption on Fe-(oxyhydr)oxides and concomitant oxidation of As(III) by dissolved O2. This reaction can be catalyzed by microbial activity or by strongly oxidizing radical species known to form upon oxidation of Fe(II) by dissolved O2. Such catalyzed oxidation reactions have been invoked to explain the enhanced kinetics of As(III) oxidation in aerated water, in the presence of zerovalent iron or dissolved Fe(II). In the present study, we used arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy to investigate the role of Fe(II) in the oxidation of As(III) at the surface of magnetite and ferrihydrite under oxygenated conditions. Our results show rapid oxidation of As(III) to As(V) upon sorption onto magnetite under oxic conditions at neutral pH. Moreover, under similar oxic conditions, As(III) oxidized upon sorption onto ferrihydrite only after additi...
TL;DR: In this paper, a novel process for the preparation of Fe3O4-loaded activated carbon (MY) was developed using waste biomass, and the composite exhibited high surface area of 349 m2/g, pore volume of 0.20 cm3/g and iron of 39.1 kg for arsenate adsorption.
TL;DR: In this paper, the authors have investigated the arsenic removal by the membrane-based nanofiltration (NF) technique and demonstrated that arsenate ions removal by NF with a high rejection of 99.80% along with total dissolved solids (TDS) and other contaminates were achieved.
TL;DR: A large vibrational spectroscopic database is provided for comparison of As(III) and As(V) speciation in aqueous solutions and at the iron oxide - solution interface to contribute to a better understanding of arsenic complexation by iron oxides.
TL;DR: In this paper, the authors investigated the role of pH in the concurrent mobilization of mackinawite (FeS) and arsenic under oxidizing conditions and showed that at neutral pH, FeS is oxidized via both the solution-phase oxidation following FeS dissolution and surface-mediated oxidation mechanisms.
TL;DR: In this paper, the potential for As partitioning into As- and Fe-sulfide minerals in anaerobic, semi-continuous flow bioreactors inoculated with 0.5% fine-grained alluvial aquifer sediment was examined.
TL;DR: ExAFS results demonstrate that As(III), as the only As species present in the raw water, does not form an aqueous complex with other metal ions, as suggested by the EDX and XPS analysis.
Abstract: Removal and recovery of high levels of arsenic (As) in copper smelting wastewater present a great environmental challenge. A novel approach was investigated for the first time using TiO2 for As adsorptive removal from wastewater and subsequent spent adsorbent regeneration and As recovery using NaOH. EXAFS results demonstrate that As(III), as the only As species present in the raw water, does not form an aqueous complex with other metal ions. An average of 3890 ± 142 mg/L As(III) at pH 1.4 in the wastewater was reduced to 59 ± 79 μg/L in the effluent with final pH at 7 in the 21 successive treatment cycles using regenerated TiO2. Coexisting heavy metals including Cd, Cu, and Pb with concentrations at 369 mg/L, 24 mg/L, and 5 mg/L, respectively, were reduced to less than 0.02 mg/L. As(III) adsorption followed pseudosecond-order rate kinetics, and the adsorption behavior was described with the charge distribution multisite surface complexation model. Approximately 60% As(III) in the waste solution after the ...
TL;DR: In this article, a new type of flexible carbon fabric supported magnetite multiwalled carbon nanotubes (Fe3O4-MWNTs) nanocomposite based supercapacitor was fabricated for the removal of high concentration of arsenic and desalination of seawater.
Abstract: A new type of flexible carbon fabric supported magnetite multiwalled carbon nanotubes (Fe3O4-MWNTs) nanocomposite based supercapacitor was fabricated for the removal of high concentration of arsenic and desalination of seawater. MWNTs were synthesized by a chemical vapor deposition (CVD) technique, purified by air oxidation and acid treatment followed by further functionalization. Decoration of magnetite (Fe3O4) nanoparticles over functionalized MWNTs surface was done by a chemical technique. Fe3O4-MWNTs nanocomposite was characterized using different characterization techniques. Electrochemical activity of the nanocomposite was analyzed for arsenite and arsenate ions containing water as well as for seawater by using cyclic voltametry (CV). Adsorption isotherms and kinetic characteristics of sodium, arsenate, and arsenite ion removal were studied. Performance of the filter made up of nanocomposite-based electrodes was examined by an inductive coupled plasma optical emission spectroscopy (ICP-OES) techniqu...