Increase In Arsenic Concentration Research Articles

Impact of the Interruption Duration on Photoluminescence Properties of MOCVD-Grown GaAsP/InAlGaAs Quantum Well Structures

The growth interruption technology is introduced to the growth of GaAsP/InAlGaAs quantum well (QW) structure using metal–organic chemical vapor deposition (MOCVD). The effect of growth interruption time (GIT) on the crystalline quality and optical properties are investigated. The two distinctive emission peaks are the transition recombination between the electron level of conduction band and the light and heavy hole level of valence band in the photoluminescence (PL) at room temperature. The PL peaks present a redshift and merge together with the increasing GIT, which is attributed to the QW energy level shift caused by the increase in arsenic concentrations in GaAsP QW, the diversified thickness of QW and the variations of indium components in the InAlGaAs barrier layer. The Gaussian deconvolution parameters in temperature-dependent PL (TDPL) show that the GaAsP/InAlGaAs QW with a GIT of 6 s has a 565.74 meV activation energy, enhancing the carrier confinement in QW and the PL intensity, while the 6 s-GIT GaAsP QW has the increasing interface roughness and the non-radiative centers at the InGaAsP intermediate layer, leading to a spectral broadening. The QW with 10 s-GIT exhibits a small full width at half maximum (FWHM) with the various temperature, indicating reduced interface roughness and excellent crystal quality. An increase in GIT may be suitable for optimizing the optical properties of GaAsP/InAlGaAs QW.

The origin and mineralization processes of the Dulenggou copper-cobalt deposit in the East Kunlun orogenic belt, western China

The East Kunlun region in western China stands out as an important polymetallic metallogenic belt hosting economically significant Au, Cu, Fe, Pb, Zn, Sn, Co, Ni and Cr resources. Within this belt lies the Dulenggou deposit, a notable Cu-Co deposit. Three cobalt minerals (cobaltine, siegenite, and glaucodot) and four nickel minerals (ullmannite, gerdorffite, violarite, and millerite) coexisting with chalcopyrite and pyrite were identified in the Dulenggou deposit. The mineralization of Co and Ni primarily occurs in the form of sulfarsenides (cobaltine and gersdorffite) rather than sulfides (siegenite and ullmannite). Sulfides are commonly associated with chalcopyrite, whereas sulfarsenides coexist with chalcopyrite occasionally within the host rocks. The presence of organic-rich surrounding sedimentary rocks reduces oxygen fugacity, and the increase in arsenic content may influence the paragenetic association of minerals. The sequence of mineral formation is Py0 (host rocks) → PyI + Ccp + Co-Ni minerals (the major mineralization stage) → PyII. The mineralization age of the Dulenggou deposit has been determined by in situ U–Pb dating of hydrothermal monazite in closely association with chalcopyrite and Co–Ni minerals, yielding an age of 467 ± 17 Ma. The δ34S values of sulfides (pyrite and chalcopyrite) from ores and host rocks range widely from 1.9 ‰ to 22.1 ‰. From Py0 to PyI to PyII to chalcopyrite, the δ34S values change from 17.6 ‰ to 22.1 ‰, from 9.1 ‰ to 14.6 ‰, from 1.9 ‰ to 7.7 ‰, and from 9.6 ‰ to 13.4 ‰, respectively. The positive δ34S values suggest that the primary sulfur source possibly originated from seawater and/or the host rocks. Based on the geological and geochemical characteristics, the Dulenggou copper-cobalt deposit is identified as a syngenetic sea floor sedimentary exhalative deposit.

Accumulation of aluminium and arsenic in Cenococcum geophilum sclerotia from forest soil affected by mining smoke

ABSTRACT Aluminium toxicity may increase under low soil pH, and an increase in arsenic concentration in the soil may inhibit inorganic P uptake and influence fungal growth. This study investigated metals/metalloids accumulation in Cenococcum geophilum sclerotia collected from highly polluted forest soils affected by mining activities and smoke hazards. The Al and As concentrations in sclerotia were 11,700 ± 823 and 10.0 ± 1.29 mg kg−1, respectively. TOF-SIMS ion mapping confirmed the predominant presence of Al as Al oxalate, acetate, and hydroxides, and the segregation of As showed higher intensities for organic As ions than inorganic As. Ion fragments of Al and As compounds were widely observed in sclerotial medulla and were generally elevated towards the central part coexisting with phosphoric acid ions. The mechanism of Al and As accumulation has been discussed to involve two biotransformation pathways in terms of sclerotial development using 14C dating. Because the sclerotia were significantly older than the historical smoke hazard and Al and As concentrations in sclerotia were high regardless of age, their accumulation were more likely to be promoted in the mature stage. This study provides insight into the contribution of ectomycorrhizal fungi and their sclerotia to soil ecosystems under metals/metalloids toxicity.

Effect of dry-wet cycles on leaching behavior of recovered soil collected from tsunami deposits containing geogenic arsenic

Geogenic contaminants, such as arsenic, are often found in soil recovered from coastal areas. These contaminants may leach out when the soil is used as embankment material. Moreover, the leaching of such contaminants might be influenced by environmental changes, such as dry-wet cycles, and higher environmental risks due to a larger amount of leaching are anticipated in some cases. In this study, therefore, soil recovered from tsunami deposits was subjected to dry-wet cycles under three different drying conditions to investigate how environmental changes affect the leaching behavior. To evaluate the physical and chemical changes in the soil surface, microscopic/spectroscopic studies were conducted. Batch leaching tests revealed that dry-wet cycles slightly alter the leaching behavior of most elements, such as Fe, Si, Na, Ca, etc. Arsenic leaching was seen to increase in certain dry-wet cycles before decreasing, and microscopic/spectroscopic confirmed that this increase was likely due to pyrite oxidation. These dry-wet cycles can disintegrate pyrite morphology and cause pyrite oxidation, leading to a more acidic leaching condition that accelerates arsenic leaching. After a certain oxidation procedure, the resulting ferric hydroxide may prevent the pyrite surfaces from further oxidation. The Fe oxides and hydroxides can also act as arsenic adsorbents, preventing the increase in arsenic concentration.

Factors causing the increase in arsenic concentration in brown rice due to high temperatures during the ripening period and its reduction by applying converted furnace slag

It has been pointed out that the concentration of arsenic (As) in brown rice increases due to high temperatures during the ripening period, and fertilization that can reduce As in brown rice even under high-temperature is required. The effectiveness of using converted furnace slag (CFS) to reduce the As concentration in brown rice was investigated. Rice plants were cultivated in Wagner pots (1/5000a) filled with gray lowland soil added CFS under ambient conditions up to 1 week after heading. Those pots were moved to a temperature gradient chamber set at four temperature levels (ambient, mildly-high, moderate-high, and super-high) and kept until harvest. An analysis of covariance using the mean daytime temperature as a covariate showed significant linearity of regression for As concentrations, indicating that high temperature increased the concentration of As in brown rice. The application of 30 g of CFS significantly reduced 20% of the As concentration in the rice, suggesting that CFS can be an effective countermeasure to reduce the As concentration in brown rice under high-temperature conditions. Since inorganic As flows into brown rice through sieve tubes, the cause of the increase in As concentration in brown rice due to high temperature was investigated by comparing the concentrations with carbon dynamics. The significant positive correlation between the As/carbon ratio and the As concentration in brown rice was observed, suggesting that high temperature reduces the rate of carbon translocation which is one of the essential factors in the increase in As concentration in brown rice due to high temperature.

Metabolomics Analysis of Chronic Exposure to Dimethylarsenic Acid in Mice and Toxicity Assessment of Organic Arsenic in Food.

Dimethylarsenic acid is a natural organic arsenic in seafood and one of the important metabolites of inorganic arsenic, which is generally considered to have low or no toxicity. However, due to the controversy of the toxicity of organic arsenic, the food safety standard of organic arsenic has not been established until now, and the effects of organic arsenic on chronic toxicity and the overall metabolic level of animals are rarely reported. In our study, 64 female C57BL/6 mice were exposed to different concentrations of dimethylarsenic acid with water intake. Fifteen metabolites in serum were detected to be altered with the increase of arsenic concentration and exposure time. Dimethylarsenic acid exposure significantly affected the overall metabolic level of mice, and the related effects were not recovered shortly after the suspension of arsenic intake. Although arsenic was excreted largely in urine and feces, continued dimethylarsenic acid exposure could still lead to arsenic accumulation in the liver and kidneys and cause mild nephritis in mice.

Histone demethylase JHDM2A participates in the repair of arsenic-induced DNA damage in L-02 cells by regulating DDB2.

Arsenic is widely present in nature and is a class I carcinogen confirmed by the World Health Organization and the International Agency for Research on Cancer. The liver is responsible for biotransformation in the body and is one of the major organs where arsenic accumulates in the body, but the mechanisms of arsenic-induced abnormal DNA damage repair pathways in the liver are still unclear. Recent studies have revealed that epigenetic mechanisms play an important role in arsenic-induced lesions. In this study, an in vitro model was established using human normal hepatocytes L-02 to investigate the mechanism of the specific demethylase JHDM2A of H3K9me2 in the repair of arsenic-induced DNA damage in L-02 cells. The results showed that with the increase of arsenic concentrations, the extent of DNA damage in L-02 cells showed an increasing trend and total intracellular H3K9me2 expression was downregulated. In addition, the enrichment level of H3K9me2 in the promoter region of DBB2, a key factor of nucleotide repair (NBR), increased, while protein and mRNA expression levels showed a decreasing trend. Thereafter, we overexpressed and repressed JHDM2A and found a close association between JHDM2A and arsenic-induced DNA damage. DDB2 protein and mRNA expression was downregulated with JHDM2A overexpression and upregulated with JHDM2A repression, while DBB2 promoter region H3K9me2 enrichment levels remained at a high level, although they were affected after JHDM2A overexpression or knockdown to some extent. These results suggest a potential mechanism by which JHDM2A may regulate DDB2 gene expression, participate in the NBR process, and play a role in arsenic-induced DNA damage in L-02 cells, which is not the result of JHDM2A exerting demethylation on H3K9me2 in the DDB2 promoter region. Our results provided an epigenetic mechanism for endemic arsenicosis, as well as a scientific basis for potential prevention and control measures.

Enhanced removal of arsenic from aqueous solution by novel red mud porous beads: batch and column experiments

Abstract Arsenic contamination in groundwater and rivers has become a major problem around the world, and may cause severe environment pollution and human health problems. In this study, cost-efficient adsorbent red mud porous beads (RPB), using red mud – a kind of alumina industry by-product, was synthesized for adsorptive removal of arsenic(V) from aqueous solution. Kinetic studies showed that chemisorption mainly governed the adsorption process. The experimental data were fitted well using the Langmuir isotherm, and the equilibrium adsorption capacity for arsenic of 11.758 mg/g at pH = 7 conditions. The effect of pH showed that the pHpzc of RPB was 6.0 and at pH = 6 the removal rate reached nearly 100%. The removal rate decreased from 91.3% to 79.0% with increase in the initial concentration of arsenic from 2.5 to 20 mg/L. The adsorption performance from column studies illustrated that the velocity of flow and the initial concentration influenced the breakthrough time of the column. This study would facilitate the use of red mud, which can be fabricated into RPB, acting as a valuable adsorbent for removing arsenic in aqueous solutions.

Neurobehavioural and Neurochemical Changes in Arsenic Induced Cerebellar Toxicity in Male Sprague-Dawley Rats: An Experimental Study

Introduction: Sodium arsenite, an inorganic arsenic, is naturally present at high level (>50 μg/L) in ground water. Drinking ground water is the biggest threat to public health. Though, there are numerous reports on arsenic neurotoxicity, the arsenic effect on cerebellar neurotoxicity remains vague especially its chronic effect on its neurobehavioural and neurochemical alterations. Aim: To evaluate the neurobehavioural and neurochemical alterations caused by sodium arsenite in cerebellum of rats. Materials and Methods: This experimental study was conducted in the Central Animal House at Sri Devaraj Urs Academy of Higher Education and Research (SDUAHER) from November 2019 to February 2020 for a period of 90 days. Total 16 male spraguedawley rats were randomised into two equal groups. Group I: Control, received normal saline. Group II: Sodium arsenite, Doses of 50 Parts per Millions (PPM) for 90 days through oral gavage. Rats were subjected to Open Field Test (OFT) for locomotor and exploratory behaviour and Beam Walking Test (BWT) for motor coordination and balance. Following behavioural tests, rats were anaesthetised. Blood was drawn from a retro-orbital puncture. Brains were dissected and cerebellum was separated. Concentration of Malondialdehyde (MDA), Nitric Oxide (NO) and activity of Glutathione Peroxidase (GPx) were assessed spectrophotometrically in serum and cerebellum of rats. Mean±SD was used for normally distributed data and groups were compared using independent t-test, whereas for non normally distributed data, Median (25th-75th Percentile) was used and Mann-Whitney U-test was used to compare between two groups. Results: Arsenic-treated rats showed a significant increase in arsenic concentration in serum and cerebellum (5.5±1.6 ng/mL, 2.76±0.56 µg/g, respectively) compared to control (1.14±0.43 ng/mL, 0.65±0.29 µg/g, respectively). There was a significant decrease in locomotor and exploratory behaviour and impairment in motor coordination and balance in arsenic treated rats with a p-value <0.001 in comparison with control rats. The arsenic treated rats had significantly enhanced concentration of MDA and NO level and reduced activity of GPx in serum {16.84 (13.84-18.87), 33.79 (30.05-37.17) nmol/mL, and 6.89 (5.24- 8.5) mmoles of Reduced glutathione (GSH) oxidised/min/mL, respectively} compared to control {8.81 (8.36-9.48), 17.66 (15.33-21.29) nmol/mL, and 15.16 (12.77-16.59) mmoles of GSH oxidised/min/mL, respectively} and also found increased concentration of MDA and NO level and reduced activity of GPx in tissue {7.98 (7.14-8.92), 24.67 (21.4-28-22) nmol/mg of protein and 2.66 (1.19-3.86) mmoles of GSH oxidised/min/ mg protein, respectively} compared to control {3.02 (2.35-3.61), 13.93 (11.0-16.16) nmol/mg of protein and 7.63 (7.08-9.19) mmoles of GSH oxidised/min/mg protein, respectively}. Conclusion: The oral administration of sodium arsenite at the doses of 50 PPM for 90 days showed interesting alterations in neurobehavioural and neurochemical parameters related to cerebellum of rats.

English

Industrial development has caused the contamination of the environment, leading to biodiversity loss and human health concerns. The use of native plants and/or their associated microbiota is a sustainable solution for reducing or transforming contaminants into less harmful forms. This study was conducted to evaluate the remedial potential of Uroclhoa mosambincensis in soils contaminated with arsenic. In a greenhouse experiment, seedlings of U. mosambincensis were divided into four treatments of increasing arsenic concentration. It was found out that in U. mosambicensis, although most physiological parameters were affected, in 200 mg.kg-1 arsenic trioxide concentration (As2O3) an increase in 23.3% of leaf biomass was observed. Chlorophyll A was not significantly affected by the presence of arsenic. It was also verified that the increase in arsenic concentration stimulated the removal of arsenic from soil to plant tissues at a percentage of 10.8, 27.7 and 30.2 higher in each treatment. This indicates the arsenic accumulator character of U. mosambicensis and its potential use for remediation of soils contaminated with arsenic.   Key words: Accumulation, arsenic trioxide, metalloid, phytoremediation.

Comparison of the effects of competitive adsorption and reductive dissolution on migration of arsenic in lake sediment

ABSTRACT Arsenic-contaminated sediment of Lake Yangzonghai (Yunnan province, China) and its overlying water was used to investigate the effects of phosphate ion (PO4 3−) and microbial activity on the migration of arsenic in the sediment. The results showed that the competitive adsorption of PO4 3− was the primary factor for the release of arsenic from the sediment to the overlying water, while microbial activity played a minor role in promoting the reductive dissolution of iron/arsenic (hydro) oxides. The reductive dissolution of ferrous ion (Fe2+) occurred in the initial stage, and partly contributed to the increase of arsenic concentration in the overlying water. The increase of PO4 3− concentration in the overlying water enhanced the mobility and biological toxicity of the arsenic in the sediment. After PO4 3− in the overlying water was depleted, arsenic in the overlying water could be adsorbed and precipitated again by iron salts, resulting in the decrease of arsenic concentration in the overlying water. The study implies that among those arsenic-contaminated lakes, eutrophication will aggravate the risks of secondary pollution of arsenic.

Effect of arsenic-contaminated irrigation water on growth and elemental composition of tomato and cabbage cultivated in three different soils, and related health risk assessment

This study was carried out to determine the effect of arsenic on tomato and cabbage cultivated in sand, sandy silt, and silt soil, and irrigated with water containing arsenic at concentrations 0.05 and 0.2 mg/L. Increasing arsenic in irrigation water did not affect the photosynthetic machinery. The chlorophyll content index increased in case of all soils and was dependent on the soil nitrogen, phosphorous, and plant biomass. Arsenic concentrations of 0.05 and 0.2 mg/L did not display any phytotoxic symptoms other than reduction in biomass in some cases. In cabbage, arsenic treatment of 0.2 mg/L increased the overall plant biomass production, while in tomato there was a decrease in aerial part and fruit biomass. The biomass production of both plants treated with different concentrations of arsenic, in the three soils was in the following order: silt > sand > sandy silt. Increase of arsenic in the irrigation water resulted in increase in arsenic concentration in the root and aerial part of both plants, at the same cultivation parameters. But tomato fruits displayed a decrease in arsenic accumulation with higher arsenic treatment. In both plants, the arsenic concentration in the plant parts changed in the following order: root > aerial part > fruit. Cabbage accumulated approximately twenty-fold more arsenic in the edible part (0.10–0.25 mg/kg DW) as compared to tomato (0.006–0.011 mg/kg DW) and displayed a good correlation with soil extractable arsenic. When cabbage was cultivated in three different soils applying the same irrigation water, it accumulated arsenic in the following order: sand > sandy silt > silt (p < 0.001 at 0.05 mg/L and p < 0.01 at 0.2 mg/L arsenic treatment). In tomato, the difference in arsenic accumulation among different soil types was highly significant (p < 0.001) but the accumulation pattern varied with the arsenic treatment applied. Sandy soil with the lowest total soil arsenic (4.32 mg/kg) resulted in the highest arsenic concentration in both plants. Among all soils and plants, the transfer factors and bioaccumulation factors were higher in sandy soil, and in cabbage. The estimated daily intake and hazard quotient values for arsenic were lower than 1 in all cases, implying no non-cancerous health risks at the arsenic concentrations applied in our study. Among nutrients only P showed a slight decline with increasing arsenic concentration while all other elements (Mg, K, Ca, S, Si, Fe, Mn, Cu, Zn) did not display any significant changes.

Effect of Arsenic Toxicity on Chlorophyll Content and Antioxidative Enzymes Activities in Rice Seedlings

Aims: Arsenic (As) contamination in rice is at alarming level as majority of rice growing regions in India are As contaminated. Present investigation is designed to study the better understanding of the physiological and biochemical mechanisms in the amount of chlorophyll change and antioxidative enzymes activity under arsenic stress on rice variety IET-4786 (Shatabdi).&#x0D; Study Design: Completely Randomized Design.&#x0D; Place and Duration of Study: The experiment was carried out in the departmental laboratory of Plant Physiology, Bidhan Chandra Krishi Viswavidyalaya (BCKV), Mohanpur, Nadia,West Bengal during the year 2017-18.&#x0D; Methodology: Two classes of inorganic arsenic- As(V) in the form of Sodium arsenate (Na2HAsO4.7H2O, M. W. = 321.01) and As(III) in the form of Sodium arsenite (NaAsO2, M.W. =129.91) were added to the modified Hoagland nutrient solution@ 2.5, 5.0, 7.5, 10.0, 12.5,15.0 mg L-1concentration. After 20 days of treatment, rice seedlings under arsenate/arsenite treatments were analyzed for change in total chlorophyll content and antioxidative enzymes activity such as superoxide dismutase (SOD: EC 1.15.1.1), catalase (CAT: EC 1.11.1.6), ascorbate peroxidase (APX: EC1.11.1.11) and peroxidase (POD: EC 1.11.1.7).&#x0D; Results: A noticeable decrease in total chlorophyll content was observed with arsenic treatments as compared to control. Various antioxidative enzymes showed significant variable response upon exposure to As(III) and As(V). SOD activities increased at low arsenic exposure up to 7.5 mg L-1 but decreased with further increase in arsenic treatments. APX and POD activities were increased with increase in arsenic concentrations while CAT activity displayed decreasing trend.&#x0D; Conclusion: The results are suggestive of differential metabolism of As(III) and As(V) in rice and could exert harmfulness in the early development stage of rice at inappropriate concentrations.

Arsenic pollution in Quaternary sediments and water near a former gold mine

Contamination of water and sediments with arsenic and heavy metals is a global issue affecting human health. Regions covered with Quaternary deposits have received little attention from the point of view of the flux of arsenic and heavy metals from sediments to surface water. This study aims to determine the flux of arsenic and other heavy metals from Quaternary sediments to surface waters in an area affected by the former Złoty Stok gold and arsenic mine. Contamination in surface waters and sediments was caused by arsenic, whereas concentrations of metals were usually within water quality standards. Arsenic contamination of surface water increased in the lower part of the basin covered by Quaternary sediments, and exceeded water quality standards by 2 orders of magnitude. Arsenic mass flux exceeded 8 kg/day near the confluence of the Trująca River with the Nysa Kłodzka, a main tributary of the Oder River. An increase in arsenic concentration in the lower part of the basin is related to mine tailings and preferential flow of groundwater through Quaternary sediments. In future, water resources scarcity may lead to an increase in arsenic contamination in surface and groundwater.

Dose-response meta-analysis of arsenic exposure in drinking water and intelligence quotient.

Exposure to inorganic arsenic through drinking water is a threat for public health. Using the arsenic-containing water in the long-term causes a variety of skin diseases, high blood pressure, and skin cancer. Arsenic also damages the nervous system. A wide range of studies have studied the effect of arsenic in drinking water on the level of intelligence in children. For the purpose of our research, we searched three electronic databases including Scopus, Web of Science, and Medline (PubMed) in English from 2000 to January 2018. We used the dose-response meta-analysis through applying random effect models in order to estimate the pooled association (with a 95% uncertainty) between water arsenic concentration and intelligence level. Using a two-stage random effect model to investigate the dose-response association between arsenic concentration and Intelligence Quotient scale, we estimated a significant linear association as -0.08 (95% CI: -0.14, -0.01). Actually, for each unit increase in arsenic concentration (one microgram per liter), intelligence quotient scale decreases by 0.08%. Considering the significance of the relationship between arsenic concentration in drinking water and the level of intelligence quotient as an important factor in training, the level of arsenic and its associated risks should be decreased in water resources.

Effect of arsenate and Arsenite on early seedling growth of rice

Presence of arsenic in ground water is a grave concern now as it is used for drinking and crop irrigation. Arsenic load of soil in the areas of arsenic contaminated ground water is gradually increasing as more than 95% of such contaminated ground water is used for crop irrigation. An experiment was conducted to study effect of arsenate and arsenite on germination and early seedling growth of the popular rice variety shatabdi. Rice seeds were exposed to water contaminated with different concentrations (Control, 2, 4, 6, 8 and 10 ppm) of arsenate and arsenite during germination and seedling growth. Observations were taken on germination at every 24 hour interval up to seven days. Seedling length (cm) and dry weight (g) recorded after seven days and plant height stress index (PHSI) and tolerance index (TI) was calculated. The speed of germination under arsenate at 2 ppm and 4 ppm was at par with the control treatment and under further higher concentration of arsenate and in all concentrations of arsenite it was lower than the control treatment. Length of seedlings, dry weight of seedlings was found to decrease with increase in concentration of arsenic. Such decrease was higher in arsenite than arsenate. The results indicate that arsenate beyond 4 ppm and arsenite beyond 2 ppm only affected germination. But seedling growth was very sensitive to arsenic and was affected at all concentrations of arsenate and arsenite. Arsenite appeared to be more toxic than arsenate.

Development of zirconia nanoparticle-loaded hydrogel for arsenic adsorption and sensing

A novel zirconia nanoparticle-loaded synthetic polymeric hydrogel was developed as an adsorbent and quartz crystal microbalance (QCM) sensor for arsenic in an aqueous solution. The bulk composite hydrogel was prepared by polymerizing a pre-gel aqueous solution containing N,N-dimethylacrylamide as the primary monomer, a crosslinking monomer, an initiator, and commercially available zirconia nanoparticles. The hydrogel-coated QCM sensor was simply fabricated by polymerizing the pre-gel aqueous solution onto the surface of a gold electrode on a quartz crystal. The hydrogel selectively adsorbed As(III) and As(V), and the adsorption equilibrium followed the Langmuir-type isotherm. The amount of arsenic adsorbed was higher in acidic and neutral solutions and decreased with an increase in pH. Moreover, the hydrogel adsorbed/desorbed arsenic repeatedly via the regeneration process using a NaOH aqueous solution. Furthermore, the investigation of the oscillation behavior of the hydrogel-coated QCM sensor revealed that the resonance frequency shift increases with an increase in arsenic concentration, which indicates that the adsorption of arsenic onto the sensor follows a Langmuir-type isotherm. The hydrogel-coated QCM sensor could detect arsenic with high selectivity and sensitivity even in the presence of Na(I), Mg(II), and Ca(II) ions. Thus, we successfully developed the world's first QCM sensor for arsenic.

Research on Arsenic Release in Ground-Water-Based Distribution System

The concentration of arsenic in effluent can meet standard requirements for drinking water after strengthening arsenic removal process, which is less than 10 μ g/L and stability in 5 ∼ 8 μ g/L. However, residual arsenic deliveries and releases in water distribution system by particle adsorption, migration, desorption and solution effect. Resulting in the water users’ arsenic concentration increases. This research aims to study the arsenic enrichment characteristics, arsenic release rule in water distribution system and the relationship between arsenic release and the other water quality parameters through the network residual arsenic census and monitoring indexes of water quality.

Diffusion coefficient of cupric ion in a copper electrorefining electrolyte containing nickel and arsenic

Diffusion and convection are the main modes of mass transport that occur during copper electrorefining. Diffusion determines the rate of copper transfer across the diffusion layer, which in turn, affects the dissolution of the anode and deposition on the cathode. The diffusion coefficient of cupric ion (DCu(II)) is a typical property that can be defined from the limiting current density (jlim) values. In this work, the limiting current densities were measured for 24 different synthetic copper electrolytes over a temperature range of 50–70 °C using a rotating disc electrode (RDE). From this data, a model for jlim and the corresponding models for DCu(II) were constructed using Levich (Model L), Koutecký-Levich (Model K) and mixed-control Newman equations (Model M). The models for jlim and DCu(II) were designed, refined and analyzed using the modeling and design tool MODDE, with the temperature, copper, nickel, arsenic and sulfuric acid concentrations as variables. Results from this research show for the first time that an increase in arsenic concentration has a reciprocal effect on the DCu(II) under copper electrorefining conditions. Furthermore, the models were validated with 11 industrial electrorefining electrolytes with known compositions. Model L (DCu(II) based on Levich equation) was shown to provide the highest correlation with the industrial solutions when compared to the other models (Model K and M) considered and previously published diffusion coefficient models. Overall, this work provides an explanation for the previously observed data variances in the literature, investigates for the first time the combined effect of parameters on DCu(II) value in industrial copper electrolysis and clarifies the effect of arsenic on the DCu(II) of copper electrorefining electrolytes.

Screening of Basmati Rice Varieties for their Arsenic Accumulation in Punjab, North-West India

ABSTRACTA pot study was conducted to screen different basmati rice varieties for their accumulation of arsenic (As). Different amounts of arsenic (0–800 µg/L) were applied through irrigation water to four basmati rice varieties (Pusa basmati-1121, Pusa Punjab basmati-1509, Punjab basmati-2, and Punjab basmati-3). Highest arsenic concentration was found in the grains of Punjab basmati-3 and lowest in the grains of Pusa Punjab basmati-1509. In all varieties, grain As concentration ranged from 0.038 to 0.288 mg/kg, which was within the permissible limit of 1.0 mg/kg in rice grain recommended by World Health Organization (WHO). In husk, highest As concentration was found in Pusa basmati-1121 and lowest in Punjab basmati-2. Among the four varieties, highest content of As was accumulated in roots and straw of Pusa Punjab basmati-1509, whereas least was accumulated in Punjab basmati-2. The distribution of arsenic among plant parts was found in the order: roots > straw > husk > grain. The mean arsenic concentrations in grain, husk, straw, and root of basmati rice varieties increased with increasing concentration of arsenic in irrigation water. Highest grain yield was obtained in Pusa Punjab basmati-1509 variety due to lesser accumulation of arsenic compared with other varieties. Rice yield, plant height, root weight, straw weight, test weight, effective tiller, and filled grain per panicle decreased with increase in arsenic concentration in irrigated water.