Excess Arsenic Research Articles

A comparative analysis of sorbents of different origin to reduce the excess of arsenic in poultry meat

The study deals with a number of problems associated with the accumulation of arsenic in the body of birds. The necessity of using sorbents for reduction the negative influence of arsenic on the organism is proved. The features of the sorption effect of sorbents of different nature in poultry tissues are studied. The advantages of Echinacea-based plant sorbent based are indicated. The advantages of using vegetable sorbents as feed additives in poultry farming are proved

Soil Warming Increases Arsenic Availability in the Rice Rhizosphere

Photo source: Flickr/WorldFish Arsenic is a widely distributed toxic element that naturally occurs in minerals. One of the most common pathways for exposure is when arsenic leaches into drinking water supplies, often through natural weathering/breakdown. People are also exposed to arsenic through food and dust. Long-term exposure is linked to health problems, including skin lesions, cardiovascular disease, and cancer. Research from Bangladesh shows long-term exposure through drinking water increases the rate of morbidity by up to 60% (http://bit.ly/2fFhq6w). Understanding exposure routes and minimizing human consumption and contact with arsenic has widespread human health benefits. One crop known to take up arsenic when the element is available in soils or irrigation water is rice (Oryza sativa L.). Arsenic accumulates throughout the plant tissues including the grain that is consumed. This is concerning for people whose diets include a high proportion of rice or rice products such as regions and cultures where rice is served with most meals, those on a gluten-free diet using rice substitutes (e.g., rice milk or rice flour), and young children who are given rice crackers and rice cereals. Rice plants may be exposed to arsenic through soil or irrigation water. Because of this, the hydrological and biogeochemical processes that take place in the rhizosphere, or the soil zone around the roots of plants, influence arsenic uptake, according to Rebecca Neumann, Assistant Professor in the Department of Civil and Environmental Engineering at the University of Washington. Specifically, rice plants release oxygen from their roots when flooded, which reacts with iron, forming “plaques” along root surfaces. The iron oxide plaques scavenge arsenic, and the plants take up arsenic released from the plaques or dissolved in the soil solution. One factor that can influence rhizosphere processes, which ultimately affect arsenic accumulation in the rice grain, is soil temperature. Because global climate models predict an increase in average temperatures, Neumann and colleagues set up an experiment to determine if elevated soil temperatures would have an effect on plaque formation and arsenic uptake. Their results were recently published in Agricultural & Environmental Letters (see http://bit.ly/2vCtRUO). “We purposefully grew our plants in a system where we could image and visualize the rhizosphere,” Neumann says. The researchers grew plants in rhizoboxes (30 cm 3 20 cm 3 2.5 cm), which enabled them to sample soil porewater and perform synchrotron imaging on the plant root zone at the end of the experiment. Rice plants were kept in growing chambers, where the atmospheric and ambient soil conditions were designed to mimic conditions in Bangladesh. The elevated soil temperature treatment was 5°C higher, which is the upper limit of expected warming in the region. Globally, Bangladesh does not have the highest concentration of arsenic in rice grains; however, “arsenic contamination of rice poses a large human health problem [in Bangladesh] because rice is the staple food. So that was part of the motivation for focusing on and trying to mimic conditions that are relevant in that context,” Neumann explains. X-ray fluorescence data collected for (a,c) one plant from the 26.1°C soil-temperature treatment and (b,d) one plant from the 30.5°C soil temperature treatment. (a–b) Solid-phase iron concentrations in counts per second (cps); concentrations in both panels scale with color bar in panel (a). (c–d) Solid-phase arsenic concentrations in counts per second; concentrations in both panels scale with color bar in panel (c). The synchrotron imaging provided additional information about arsenic in the rhizosphere. The authors report that with warmer soil temperature, there was more iron plaque on roots and more arsenic sequestration. Neumann explains, “There is more arsenic mobilized and made available in the warmer temperatures. This excess arsenic, some of it [is] sequestered in the plaques, and then some of it [is taken up through] the roots.” At the end of the experiment, plants were destructively sampled to test for arsenic levels in plant tissues. The authors report the plants grown in warmer soil temperatures had greater concentrations of arsenic in the porewater, root tissue, straw tissue, and husk. However, arsenic concentrations in the grain did not change with soil temperature. Read the full study in Agricultural & Environmental Letters http://bit.ly/2vCtRUO. While this is a small data set, using a single rice cultivar and focusing only on elevated soil temperature in laboratory conditions, Neumann says the results show, “it's not just plant physiology that can change [with increased temperatures], but actually these processes in the rhizosphere.” Having established this response, Neumann hopes to investigate rhizosphere interactions in other rice cultivars and to scale up to field experiments. Understanding what changes may occur under future climate conditions enables researchers to help mitigate arsenic exposure through rice before it happens.

Environmental exposure to metals, neurodevelopment, and psychosis.

This article presents a new hypothesis about the possible relation between early life exposure to metals and psychosis. We review limitations of available research, and discuss novel approaches to overcome previous methodological barriers. Mechanistic studies suggest a possible association between excess lead, manganese, cadmium, arsenic, or copper, and zinc deficiency, and several biochemical disturbances related to psychosis, such as altered neurotransmitters levels, excitotoxicity, and inflammation. Furthermore, studies suggest that some metals (lead, manganese, cadmium excess, and zinc deficiency) are associated with schizophrenia or psychosis-related phenotype. However, previous studies had multiple methodological limitations. Importantly, metal exposure was often measured after disease development and seldom determined during critical developmental periods. Most studies fell short of depicting the exact timing of exposure and the change in exposure over time. Here, we propose several methods to overcome these methodological limitations. There is a plausible role of early life exposure to metals in the cause of psychosis. Owing to methodological limitations in exposure measurement, this has not been well characterized. Considering the wide exposure to metals and the high cost of psychosis to society, this hypothesis should be rigorously examined.

Spatially correlated two-dimensional arrays of semiconductor and metal quantum dots in GaAs-based heterostructures

A single molecular-beam epitaxy process is used to produce GaAs-based heterostructures containing two-dimensional arrays of InAs semiconductor quantum dots and AsSb metal quantum dots. The twodimensional array of AsSb metal quantum dots is formed by low-temperature epitaxy which provides a large excess of arsenic in the epitaxial GaAs layer. During the growth of subsequent layers at a higher temperature, excess arsenic forms nanoinclusions, i.e., metal quantum dots in the GaAs matrix. The two-dimensional array of such metal quantum dots is created by the δ doping of a low-temperature GaAs layer with antimony which serves as a precursor for the heterogeneous nucleation of metal quantum dots and accumulates in them with the formation of AsSb metal alloy. The two-dimensional array of InAs semiconductor quantum dots is formed via the Stranski–Krastanov mechanism at the GaAs surface. Between the arrays of metal and semiconductor quantum dots, a 3-nm-thick AlAs barrier layer is grown. The total spacing between the arrays of metal and semiconductor quantum dots is 10 nm. Electron microscopy of the structure shows that the arrangement of metal quantum dots and semiconductor quantum dots in the two-dimensional arrays is spatially correlated. The spatial correlation is apparently caused by elastic strain and stress fields produced by both AsSb metal and InAs semiconductor quantum dots in the GaAs matrix.

Assessment Of Arsenic Induced Health Diseases In Bihar, India

Introduction There is evidence for high arsenic levels in drinking water in several Indian states, among which Bihar is severely affected. High arsenic levels have been associated with various diseases, including skin problems and cancer. Previous research indicated that, over 10 million people in Bihar are drinking water containing more than 10 ppb –part per billion – and are living in the northern Bihar Gangetic plane. In this region, the prevalence of skin lesions, skin and gall bladder cancer is increasing rapidly. We investigated the arsenic contamination of drinking water in Bihar and health status of the affected population. Methods We enrolled 3469 individuals comprise 1901 males and 1568 females from two districts of Bihar between 2012 and 2014. We determined the arsenic concentration in drinking water from 926 household hand pump chosen randomly. Demographic details, information on drinking water sources and other factors such as medical costs related to Arsenicosis disease were collected using a survey. Based on drinking water measurements, the study estimated the total population potentially exposed to excess arsenic in both the districts. Results We found that the drinking water quality (excess of iron and arsenic in drinking water) was poor for 78.8% of the households and for 67.4% arsenic levels exceeded 10 ppb. We found that Arsenicosis disease was related to wage loss and high medical costs, being a financial burden for the affected household. The incident rate of Arsenicosis disease for entire sample, male, and female sample found to be 92, 82, and 105, respectively. Households with lower incomes would have more arsenic contamination in their drinking water. Conclusion We found that exposure to arsenic in drinking water was associated with skin lesions and gall bladder cancer. The financial burden of Arsenicosis disease results in social and economic exclusion of the affected patients and households.

Th(As(III)4As(V)4O18): a mixed-valent oxoarsenic(III)/arsenic(V) actinide compound obtained under extreme conditions.

A high-temperature/high-pressure method was employed to investigate phase formation in the Th(NO3)4·5H2O-As2O3-CsNO3 system. It was observed that an excess of arsenic(III) in starting system leads to the formation of Th(As(III)4As(V)4O18), which is representative of a rare class of mixed-valent arsenic(III)/arsenic(V) compounds. This compound was studied with X-ray diffraction, energy-dispersive X-ray, and Raman spectroscopy methods. Crystallographic data show that Th(As(III)4As(V)4O18) is built from (As(III)4As(V)4O18)(4-) layers connected through Th atoms. The arsenic layers are found to be isoreticular to those in previously reported As2O3 and As3O5(OH), and the geometric differences between them are discussed. Bands in the Raman spectrum are assigned with respect to the presence of AsO3 and AsO4 groups.

Effect of annealing on the nonequilibrium carrier lifetime in GaAs grown at low temperatures

GaAs samples grown by molecular-beam epitaxy at low (230°C) temperatures are investigated. One of the samples is subjected to aftergrowth annealing at 600°C. Using an unconventional pump-probe scheme for measuring the dynamic variation in the light refractive index, the nonequilibrium charge-carrier lifetime (275 ± 30 fs before annealing) is determined. Such a short carrier lifetime in the unannealed material is due to the high concentration of point defects, mainly AsGa antisite defects. According to X-ray diffraction and steady-state optical absorption data, the AsGa concentration in the samples is 3 × 1019 cm−3, which corresponds to an arsenic excess of 0.26 at %. Upon annealing at 600°C, the superstoichiometric As defects self-organize and form As nanoinclusions in the GaAs crystal matrix. It is shown that in this case the nonequilibrium charge-carrier lifetime increases to 452 ± 5 fs. This lifetime is apparently ensured by the capture of non-equilibrium charge carriers at metal As nanoinclusions.

Experimental evaluation of the carrier lifetime in GaAs grown at low temperature

The relaxation dynamics of nonequilibrium charge carriers in gallium arsenide epitaxial films grown by molecular-beam epitaxy at low temperatures has been studied. The growth conditions of the epitaxial layer provided an excess arsenic content of 1.2% in the layer. In a material of this kind, the carrier lifetime is <1 ps. To examine carrier relaxation in the femtosecond range, an original scheme for measuring the refractive index dynamics was developed on the basis of the pump-probe technique. The lifetime of nonequilibrium charge carriers was evaluated to be (200 ± 35) fs.

Spectroscopic ellipsometry studies of reactively sputtered nitrogen-rich GaAsN films

Nitrogen-rich GaAsN thin films have been deposited at 500°C by reactive rf sputtering of GaAs target in argon–nitrogen atmosphere. The arsenic content of the films was varied by changing the nitrogen percentage in the sputtering atmosphere and the As/Ga ratio in the films was estimated by X-ray fluorescence measurements. Spectroscopic ellipsometry measurements have been carried out on these films and the measured ellispometric spectra were fitted with theoretical spectra generated by using suitable model sample structures. From the best fit parameters of the dispersion model, band-gap values and variation of refractive index and extinction coefficient as a function of wavelength have been obtained for films deposited with different percentages of nitrogen in the sputtering atmosphere. The films deposited with 12% to 100% nitrogen in the sputtering atmosphere, which are of hexagonal GaN, exhibit GaN-like optical properties, though effects due to excess arsenic in amorphous phase are seen in the films deposited with less than 40% nitrogen. The films deposited with 5% to 12% nitrogen in sputtering atmosphere are dominantly polycrystalline GaAsxN1−x (x≈0.01 to 0.08) and exhibit variations in optical parameters, which are consistent with their structure and composition. The films deposited with less than 5% nitrogen in sputtering atmosphere are arsenic-rich and amorphous.

Etching of GaAs(100) with Aqueous Ammonia Solution: A Synchrotron-Photoemission Spectroscopy Study

Etching of the GaAs(100) surface with aqueous ammonia solution is studied by highly surface-sensitive synchrotron-radiation photoemission spectroscopy. It is shown that such treatment effectively removes the native oxide layer leaving the surface covered with elemental arsenic, as well as arsenic hydroxides AsOH and As(OH)3, gallium hydroxide GaOH, and gallium suboxide GaxO. After annealing of the surface at 500 °C, the arsenic and gallium hydroxides disappear, while the excess arsenic is dimerized. The residual carbon contamination prevents disappearance of gallium hydroxide and hinders dimerization of excess arsenic on annealing. Rinsing the etched surface with 2-propanol instead of water prior to annealing results in considerable reduction of carbon contamination after annealing.

Some critical aspects in the determination of binding constants by electrospray ionisation mass spectrometry at the example of arsenic bindings to sulphur‐containing biomolecules

The influences of reactant concentrations, solvent type, acid strength, pH conditions and ionic strength on the determination of apparent gas-phase equilibrium constants K using electrospray ionisation mass spectrometry (ESI-MS) were elucidated. As example serves the interaction of the tripeptide glutathione (GSH) with phenylarsine oxide (PAO). It was shown that rising initial concentrations of both reactants were not adequately compensated by increasing signal intensities of the reaction products in the mass spectra. The equilibrium constant for the formation of the phenylarsenic-substituted peptide species decreased from 1.42 x 10(5) +/- 1.81 x 10(4) l micromol(-1) to 1.54 x 10(4) +/- 1.5 x 10(3) l micromol(-1) with rising initial GSH concentrations from 1 to 10 microM at fixed PAO molarity of 50 microM. K values resulting from a series with a fixed GSH molarity of 5 microM and a PAO molarity varied from 10 to 100 microM remained in a narrower range between 4.59 x 10(4) +/- 2.15 x 10(4) l micromol(-1) and 1.07 x 10(4) +/- 4.0 x 10(3) l micromol(-1). In contrast, consumption numbers calculated from the ion intensity ratios of reaction products to the unreacted peptide were not influenced by the initial reactant concentrations. In a water-acetonitrile-acetic acid mixture (48:50:2, v:v), the consumption of 5 micro M GSH increased from 8.3 +/- 1.4% to 39.6 +/- 1.6% with increased molar excess of PAO from 2 to 20, respectively. The GSH consumption was considerably enhanced in a changed solvent system consisting of 25% acetonitrile and 75% 10 mM ammonium formate, pH 5.0 (v:v) up to 80% of the original peptide amount at an only threefold molar arsenic excess.

One magic pteridophyte (Pteris vittata L.): Application in remediating arsenic contaminated soils and mechanism of arsenic hyperaccumulation

One pteridophyte, Pteris vittata L., was found to be a suitable plant used in phytoremediation of the soils contaminated with excess arsenic. In this paper, literature on this fern’s potential in remediating soils contaminated with arsenic, its possible detoxification strategies, and the measures facilitating its practical application in phytoremediation were reviewed. Some of the unresolved questions about this fern in both detoxification and phytoextraction of arsenic (As) were also listed. The aim of this paper was to introduce this magic fern to more researchers focusing on a wider field of discipline and make it more useful in both macroscopic and microcosmic science world.

Preparation of As‐rich (2x4) – III‐As (001) surfaces by wet chemical treatment and vacuum annealing

AbstractThe GaAs and InAs (001) surfaces chemically treated in HCl‐isopropanol solution (HCl‐iPA) and annealed in vacuum were studied by means of photoemission, low energy electron diffraction (LEED) and electron energy loss spectroscopy (EELS). The photoemission results demonstrated that the chemical treatment removed native oxides from Ga(In)As surfaces and yielded As‐rich surface with several monolayers of excess arsenic and small amounts of GaClx (InClx). Annealing at relatively low‐temperatures induced desorption of this overlayer and revealed a clean arsenic‐rich (2x4)/c (2x8) structure on GaAs and InAs(100) surfaces. The structural properties of chemically prepared III‐As (001) surfaces were found to be similar to those obtained by decapping of As‐capped epitaxial layers. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

A study of the interaction of gallium arsenide with wet chemical formulations using thermodynamic calculations and spectroscopic ellipsometry

This paper investigates the effectiveness of different wet chemical treatments and their ability to produce/regrow a thin, stable surface oxide layer on GaAs. Results from thermodynamic considerations indicate that a stable surface oxide layer, free of excess arsenic and arsenic oxides, can be achieved by properly choosing aqueous solutions targeted within the GaAs solubility range (pH < 3 or pH > 11) followed by deionized (DI) water rinsing. This is further corroborated by spectroscopic ellipsometric data that can qualitatively, but correctly, identify the thickness of the surface oxide layer after different wet chemical treatments. Specifically, samples treated with acidic solutions based on HCl, HF, and H 3PO 4 and diluted ammonium hydroxide solution produce a more stable surface layer that is thinner than the native oxide layer on GaAs. The results and subsequent discussion are presented in the context of an attempt at achieving a well passivated GaAs surface, free of excessive surface state defects responsible for Fermi-level pinning.

Photoluminescence of Si-doped GaAs epitaxial layers

The effect of arsenic pressure on the amphoteric behavior of Si during the growth of the Si-doped (100)-, (111)Ga-, and (111)As-oriented GaAs layers is studied by photoluminescence spectroscopy. The edge luminescence band is examined, and the concentration and the degree of compensation as functions of the arsenic pressure are determined. Nonstoichiometry defects in GaAs layers grown with a deficit and an excess of arsenic are studied. It is shown that the defects formed in the (111)Ga- and (111)As-oriented layers are different in nature.

Stoichiometric growth of high Curie temperature heavily alloyed GaMnAs

Heavily alloyed, 100nm Ga1−xMnxAs (x&amp;gt;0.1) films are obtained via low-temperature molecular beam epitaxy by utilizing a combinatorial technique which allows systematic control of excess arsenic during growth. Reproducible electronic, magnetic, and structural properties are optimized in a narrow range of stoichiometric growth conditions. In contrast to a prediction of the Zener model of hole-mediated ferromagnetism, the Curie temperature of the stoichiometric material is independent of x (for x&amp;gt;0.1), while substitutional Mn content is proportional to x within a large window of growth conditions.

Technological approaches to providing safe drinking water for rural and remote areas

Provision of safe drinking water is one of the key drivers in our technological pursuits. A number of habitations are suffering from a variety of water quality problems such as excess salinity, iron, arsenic, fluoride, nitrate and microbial contamination. Simplicity of operation, less dependence on external sources of power supply, minimisation of wastewater, etc., are some of the ground rules to ensure reliability and sustainability of water purification technologies/devices. The experience over the last two decades has indicated that the objective of providing safe drinking water in totality can be achieved only with the technologies in tune with the village environment and the total participation of the user group. Domestic water purifier based on ultrafiltration can be used as a point-of-use device in almost all households to provide microbiologically safe drinking water. With suitable modifications, these devices can be used for removal of contaminants such as iron, and marginal contamination of fluorides and arsenic. The use of reverse osmosis can tackle salinity and other contaminants. Safe quality water is costlier due to the use of the device and hence its use should be only to the extent required. It is necessary therefore to promote quality linked usage of water to ensure sustainability and reliability.

Arsenic as an Endocrine Disruptor: Arsenic Disrupts Retinoic Acid Receptor–and Thyroid Hormone Receptor–Mediated Gene Regulation and Thyroid Hormone–Mediated Amphibian Tail Metamorphosis

BackgroundChronic exposure to excess arsenic in drinking water has been strongly associated with increased risks of multiple cancers, diabetes, heart disease, and reproductive and developmental problems in humans. We previously demonstrated that As, a potent endocrine disruptor at low, environmentally relevant levels, alters steroid signaling at the level of receptor-mediated gene regulation for all five steroid receptors.ObjectivesThe goal of this study was to determine whether As can also disrupt gene regulation via the retinoic acid (RA) receptor (RAR) and/or the thyroid hormone (TH) receptor (TR) and whether these effects are similar to previously observed effects on steroid regulation.Methods and resultsHuman embryonic NT2 or rat pituitary GH3 cells were treated with 0.01–5 μM sodium arsenite for 24 hr, with or without RA or TH, respectively, to examine effects of As on receptor-mediated gene transcription. At low, noncytotoxic doses, As significantly altered RAR-dependent gene transcription of a transfected RAR response element–luciferase construct and the native RA-inducible cytochrome P450 CYP26A gene in NT2 cells. Likewise, low-dose As significantly altered expression of a transfected TR response element–luciferase construct and the endogenous TR-regulated type I deiodinase (DIO1) gene in a similar manner in GH3 cells. An amphibian ex vivo tail metamorphosis assay was used to examine whether endocrine disruption by low-dose As could have specific pathophysiologic consequences, because tail metamorphosis is tightly controlled by TH through TR. TH-dependent tail shrinkage was inhibited in a dose-dependent manner by 0.1– 4.0 μM As.ConclusionsAs had similar effects on RAR- and TR-mediated gene regulation as those previously observed for the steroid receptors, suggesting a common mechanism or action. Arsenic also profoundly affected a TR-dependent developmental process in a model animal system at very low concentrations. Because RAR and TH are critical for both normal human development and adult function and their dysregulation is associated with many disease processes, disruption of these hormone receptor–dependent processes by As is also potentially relevant to human developmental problems and disease risk.

Optically addressed As50Se50-liquid crystal structure highly sensitive to He-Ne laser radiation

An optically addressed structure of the As x Se1-x -liquid crystal (LC) type, with the photoconductor composition deviating from stoichiometry toward excess arsenic, has been tested using holographic techniques. It is established that the As50Se50-LC structure (with maximum possible arsenic content in the photoconductor) exhibits record high sensitivity (2.2 × 10−7 W/cm2) at a He-Ne laser radiation wavelength. Based on this structure, it is possible to implement nonlinear optical data-processing algorithms employing the entire transmission characteristic including the inversion region. The maximum diffraction efficiency achieved with the As50Se50-LC structure amounts to 36.5%.

Crystal structure of erbium palladium arsenic, ErPdAs

AsErPd, orthorhombic, Pnma (no. 62), a = 6.9600(9) A, b = 4.082(2) A, c = 7.862(2) A, V = 223.4 A 3 , Z =4 , Rgt(F) = 0.039, wRref(F) = 0.042, T =2 93 K. Source of material Polycrystalline sample of the ternary arsenide ErPdAs was prepared from the pure elements: amorphous -As as powder, erbium and palladium as ingots, all supplied with minimum purity grade of 99.99 %. Powder and freshly filed chips of the constituents in the nominal ratio of Er:Pd:As = 1:1:1 were mixed together and pressed into pellets. A small excess of arsenic (1 at. %) was added to compensate for possible evaporation losses during the arc melting process. Prior to melting in an arc furnace under Ti/Zr-gettered argon atmosphere, the pellets (about 1 g each) were pre-reacted in evacuated silica tubes by gradual heating them up to 1070 K, holding at this temperature for 2 days and then slow cooling down to the room temperature. The cooled buttons were remelted twice to achieve homogeneity. Finally, to reach thermodynamic equilibrium, the sample was placed into an alumina crucible and sealed in a fused silica tube, kept at 1070 K for one month and subsequently quenched into a cold water. After the sample was crushed, air-stable single crystals with prismatic form and metallic luster were extracted and used for structure determination.