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The contamination of water by arsenic (As) has emerged as a significant environmental concern due to its well-documented toxicity. Environmentally relevant concentrations of As have been reported to pose a considerable threat to fish. However, previous studies mainly focused on the impacts of As at environmentally relevant concentrations on adult fish, and limited information is available regarding its impacts on fish at early life stage. In this study, zebrafish embryos were employed to evaluate the environmental risks following exposure to different concentrations (0, 25, 50, 75 and 150 μg/L) of pentavalent arsenate (AsV) for 120 hours post fertilization. Our findings indicated that concentrations ≤ 150 μg/L AsV did not exert significant effects on survival or aberration; however, it conspicuously inhibited heart rate of zebrafish larvae. Furthermore, exposure to AsV significantly disrupted mRNA transcription of genes associated with cardiac development, and elongated the distance between the sinus venosus and bulbus arteriosus at 75 μg/L and 150 μg/L treatments. Additionally, AsV exposure enhanced superoxide dismutase (SOD) activity at 50, 75 and 150 μg/L treatments, and increased mRNA transcriptional levels of Cu/ZnSOD and MnSOD at 75 and 150 μg/L treatments. Concurrently, AsV suppressed metallothionein1 (MT1) and MT2 mRNA transcriptions while elevating heat shock protein70 mRNA transcription levels in zebrafish larvae resulting in elevated malondialdehyde (MDA) levels. These findings provide novel insights into the toxic effects exerted by low concentrations of AsV on fish at early life stage, thereby contributing to an exploration into the environmental risks associated with environmentally relevant concentrations., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest relating to the work presented in this manuscript., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Ferrihydrite is an effective adsorbent of chromate and arsenate. In order to gain insight into the application of ferrihydrite in water treatment, macroporous alginate/ferrihydrite beads, synthesized using two different methods (internal and encapsulation processes), were used in this work. The properties of the ferrihydrite were assessed using various techniques, including X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) theory, and zetametry. The results showed that the specific surface area of the ferrihydrite was 242 m 2 /g, and the PZC was pH8. The kinetic and isotherm adsorption properties of the ferrihydrite were evaluated in this study. The results indicate that the pseudo second-order and Freundlich models accurately describe the kinetic and isotherm adsorption properties of chromates and arsenates. For chromate removal, ferrihydrite exhibited a relatively high adsorption capacity (40.7 mg Cr /g) compared to other adsorbents. However, the arsenate adsorption capacity of MFHB-SI (140.8 mg As /g) was shown to be the most optimal. The internal synthesis process was suitable for arsenate retention due to the resulting arsenate precipitation. The competitive adsorption analyses indicated that the presence of chromate does not limit the adsorption of arsenate. However, the presence of arsenate almost completely inhibits the adsorption of chromate when the arsenate concentration is above 50 mg/L, due to the precipitation reaction of arsenate., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Lulu zhao reports financial support was provided by Region Nouvelle-Aquitaine. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Groundwater contamination is a global concern that has detrimental effect on public health and the environment. Sustainable groundwater treatment technologies such as adsorption require attaining a high removal efficiency at a minimal cost. This study investigated the adsorption of arsenate from groundwater utilizing chitosan-coated bentonite (CCB) under a fixed-bed column setup. Fuzzy multi-objective optimization was applied to identify the most favorable conditions for process variables, including volumetric flow rate, initial arsenate concentration, and CCB dosage. Empirical models were employed to examine how initial concentration, flow rate, and adsorbent dosage affect adsorption capacity at breakthrough, energy consumption, and total operational cost during optimization. The ε-constraint process was used in identifying the Pareto frontier, effectively illustrating the trade-off between adsorption capacity at breakthrough and the cost of the fixed-bed system. The integration of fuzzy optimization for adsorption capacity and its total operating cost utilized the global solver function in LINGO 20 software. A crucial equation derived from the Box-Behnken design and a cost equation based on energy and material usage in the fixed-bed system was employed. The results from identifying the Pareto front determined boundary limits for adsorption capacity at breakthrough (ranging from 12.96 ± 0.19 to 12.34 ± 0.42 μg/g) and total operating cost (ranging from 955.83 to 1106.32 USD/kg). An overall satisfaction level of 35.46% was achieved in the fuzzy optimization process. This results in a compromise solution of 12.90 μg/g for adsorption capacity at breakthrough and 1052.96 USD/kg for total operating cost. Henceforth, this can allow a suitable strategic decision-making approach for key stakeholders in future applications of the adsorption fixed-bed system., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The co-occurrence of uranyl and arsenate in contaminated water caused by natural processes and mining is a concern for impacted communities, including in Native American lands in the U.S. Southwest. We investigated the simultaneous removal of aqueous uranyl and arsenate after the reaction with limestone and precipitated hydroxyapatite (HAp, Ca 10 (PO 4 ) 6 (OH) 2 ). In benchtop experiments with an initial pH of 3.0 and initial concentrations of 1 mM U and As, uranyl and arsenate coprecipitated in the presence of 1 g L -1 limestone. However, related experiments initiated under circumneutral pH conditions showed that uranyl and arsenate remained soluble. Upon addition of 1 mM PO 4 3- and 3 mM Ca 2+ in solution (initial concentration of 0.05 mM U and As) resulted in the rapid removal of over 97% of U via Ca-U-P precipitation. In experiments with 2 mM PO 4 at pH rising from 7.0 to 11.0, aqueous concentrations of As decreased (between 30 and 98%) circa pH 9. HAp precipitation in solids was confirmed by powder X-ray diffraction and scanning electron microscopy/energy dispersive X-ray. Electron microprobe analysis indicated U was coprecipitated with Ca and P, while As was mainly immobilized through HAp adsorption. The results indicate that natural materials, such as HAp and limestone, can effectively remove uranyl and arsenate mixtures.3- and 10 mM Ca 2+ at pH rising from 7.0 to 11.0, aqueous concentrations of As decreased (between 30 and 98%) circa pH 9. HAp precipitation in solids was confirmed by powder X-ray diffraction and scanning electron microscopy/energy dispersive X-ray. Electron microprobe analysis indicated U was coprecipitated with Ca and P, while As was mainly immobilized through HAp adsorption. The results indicate that natural materials, such as HAp and limestone, can effectively remove uranyl and arsenate mixtures.

Assessment of inorganic arsenate (As(V)) is critical for ensuring a sustainable environment because of its adverse effects on humans and ecosystems. This study is the first to attempt to predict As(V) toxicity to the bioluminescent bacterium Aliivibrio fischeri exposed to varying As(V) dosages and environmental factors (pH and phosphate concentration) using six machine learning (ML)-guided models. The predicted toxicity values were compared with those predicted using the extended biotic ligand model (BLM) we previously developed to evaluate the toxic effect of oxyanion (i.e., As(V)). The relationship between the variables (input features) and toxicity (output) was found to play an important role in the prediction accuracy of each ML-guided model. The results indicated that the extended BLM had the highest prediction accuracy, with a root mean square error (RMSE) of 12.997. However, with an RMSE of 14.361, the multilayer perceptron (MLP) model exhibited quasi-accurate prediction, despite having been trained with a relatively small dataset (n = 256). In view of simplicity, an MLP model is compatible with an extended BLM and does not require expert knowledge for the derivation of specific parameters, such as binding fraction and binding constant values. Furthermore, with the development and employment of reliable in-situ sensing techniques, monitoring data are expected to be augmented faster to provide sufficient training data for the improvement of prediction accuracy which may, thus, allow it to outperform the extended BLM after obtaining sufficient data., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Hematite is a common iron oxide in natural environments, which has been observed to influence the transport and fate of arsenate by its association with hematite. Although oxygen vacancies were demonstrated to exist in hematite, their contributions to the arsenate immobilization have not been quantified. In this study, hematite samples with tunable oxygen vacancy defect (OVD) concentrations were synthesized by treating defect-free hematite using different NaBH 4 solutions. The vacancy defects were characterized by positron annihilation lifetime spectroscopy, Doppler broadening of annihilation radiation, extended X-ray absorption fine structure (EXAFS), thermogravimetric mass spectrometry (TG-MS), electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS). The results revealed that oxygen vacancy was the primary defect type existing on the hematite surface. TG-MS combined with EPR analysis allowed quantification of OVD concentrations in hematite. Batch experiments revealed that OVDs had a positive effect on arsenate adsorption, which could be quantitatively described by a linear relationship between the OVD concentration ( C def ) and the enhanced arsenate adsorption amount caused by defects (Δ -2 ) and the enhanced arsenate adsorption amount caused by defects (Δ Q m , μmol m -2 ) (Δ Q m = 20.94 C -DRIFT) analysis and density functional theory (DFT) calculations demonstrated that OVDs in hematite were beneficial to the improvement in adsorption strength of surface-active sites, thus considerably promoting the immobilization of arsenate.def , R 2 = 0.9813). NH 3 -diffuse reflectance infrared Fourier transform (NH 3 -DRIFT) analysis and density functional theory (DFT) calculations demonstrated that OVDs in hematite were beneficial to the improvement in adsorption strength of surface-active sites, thus considerably promoting the immobilization of arsenate.

We investigated the aqueous solubility and thermodynamic properties of two meta-autunite group uranyl arsenate solids (UAs). The measured solubility products (log K sp ) obtained in dissolution and precipitation experiments at equilibrium pH 2 and 3 for NaUAs and KUAs ranged from -23.50 to -22.96 and -23.87 to -23.38, respectively. The secondary phases (UO 2 )(H 2 AsO 4 ) 2 (H 2 O) (s) and trögerite, (UO 2 ) 3 (AsO 4 ) 2 ·12H 2 O (s) , were identified by powder X-ray diffraction in the reacted solids of KUA precipitation experiments (pH 2) and NaUAs dissolution and precipitation experiments (pH 3), respectively. The identification of these secondary phases in reacted solids suggest that H 3 co-occurring with Na or K in the interlayer region can influence the solubilities of uranyl arsenate solids. The standard-state enthalpy of formation from the elements (Δ + co-occurring with Na or K in the interlayer region can influence the solubilities of uranyl arsenate solids. The standard-state enthalpy of formation from the elements (Δ H f - el derived from measurements by drop solution calorimetry, consistent with values reported in other studies for uranyl phosphate solids. This work provides novel thermodynamic information for reactive transport models to interpret and predict the influence of uranyl arsenate solids on soluble concentrations of U and As in contaminated waters affected by mining legacy and other anthropogenic activities.-1 and for KUAs is -3000 ± 28 kJ mol -1 derived from measurements by drop solution calorimetry, consistent with values reported in other studies for uranyl phosphate solids. This work provides novel thermodynamic information for reactive transport models to interpret and predict the influence of uranyl arsenate solids on soluble concentrations of U and As in contaminated waters affected by mining legacy and other anthropogenic activities.

In an aquatic ecosystem, especially constructed wetlands receiving arsenic (As)-containing wastewater, the fate and mobility of As is influenced by manganese (Mn) oxides and organic matter. Although Mn oxides have been extensively investigated for As(V) adsorption, effects of low molecular weight organic acids (LMWOAs) with different functional groups on As(V) adsorption onto birnessite and underlying mechanisms remain elusive. In this study, LMWOAs with two carboxyl groups (including tartaric (TA), malate (MA), and succinic acids (SA) with two, one and zero hydroxyl groups, respectively) were used. Results showed that more As(V) was adsorbed on birnessite with the presence of LMWOA, indicating that the LMWOA promoted As(V) adsorption via birnessite-carboxyl-As(V) ternary complex. Before birnessite dissolution, TA and MA facilitated As(V) adsorption more efficiently than SA, indicating that hydroxyl group enhanced the coordination among carboxyl groups, As(V) and birnessite. However, within high TA/MA batches, As(V) concentrations decreased sharply and then gradually increased, but Mn(II) concentrations continuously increased, showing the initial reductive dissolution of birnessite promoted As adsorption, while further dissolution was conducive to As mobilization. This study identifies the mechanisms of As adsorption in the presence of LMWOAs and highlights the importance of functional groups in As fate and mobility in aqueous environments., (Copyright © 2022 Elsevier B.V. All rights reserved.)

We report a simple and fast method for the quantification of both phosphate and arsenate in water using the molybdenum blue method. The method does not require established pre-treatment procedures for physically separating arsenate and phosphate or reducing the arsenate to arsenite. In our method, the heteropolymolybdate ions in the solution are precipitated and collected on a membrane that is transparent in both the visible and infrared regions of the spectrum. The phosphate is determined by recording a visible spectrum in transmission mode through the membrane. This membrane is then air-dried, and then an infrared spectrum is recorded through the membrane in transmission mode. The concentration of arsenate is then determined from the intensity of an As-O band positioned at 879 cm -1 in the infrared spectrum. Using this method, a detection limit of 0.86 μg L -1 phosphate and 13.9 μg L -1 arsenate in water was achieved. Matrix spikes on environmental samples gave a 108% recovery of arsenate and a 105% recovery of phosphate over a dynamic range of 25-250 μg L -1 of arsenate and phosphate in the sample., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A novel arsenate-reducing bacterium, LY-1 T , was isolated from freshwater sediment in Huangshi, China. Morphological analysis indicated that the cells were shaped like rods and were gram-negative. The major fatty acids (> 10%) were C 16:0 , summed feature 3 (C 16:1 ω7c, C 16:1 ω6c) and summed feature 8 (C 18:1 ω7c, C 18:1 ω6c). An assessment of the phylogeny based on 16S rRNA gene sequences indicated that the strain LY-1 T belonged to the genus Citrobacter, while further analysis based on the recN gene indicated that LY-1 T occupies a distinct phylogenetic niche within the Citrobacter genus. Moreover, average nucleotide identity and digital DNA-DNA hybridization between the strain LY-1 T and the type strains of closely related species of the genus Citrobacter (C. europaeus, C. brakii, C. portucalensis, C. freundii, C. werkmanii, C. cronae, C. youngae, C. pasteurii, C. tructae, C. gillenii, and C. murliniae) were 85.8-93.8% and 31.2-56.9%, respectively. In addition, the LY-1 T strain's capacity to metabolize various compounds and its characteristic G + C content of 51.9% were also distinct from other species of the Citrobacter genus. These discriminatory features cumulatively indicate the LY-1 T strain as a new species within the Citrobacter genus. We propose the species name Citrobacter arsenatis for this new species, with LY-1 T (= CCTCC AB 2019169 T  = KCTC 72440 T ) as the type strain., (© 2021. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Castor, a non-food, dedicated bioenergy crop, has immense potential to be used for phytoremediation/revegetation of heavy metal contaminated sites. In the previous study, we identified arsenate [As(V)]-tolerant (WM) and As(V)-sensitive (GCH 2) genotypes of castor (Ricinus communis L.) with differential accumulation and tolerance of arsenic [As]. The role of thiols in As(V) toxicity and tolerance mechanism in the castor plant is not fully understood. On the one hand, thiol-dependent reduction of As(V) to As(III) by arsenate reductase (AR) makes it capable of reacting with thiol groups of protein leading to disturbed metabolic pathways; on the other hand, reduction of As(V) to arsenite [As(III)] by AR and then complexation of As(III) with phytochelatins (PCs) and compartmentalization of As(III)-PC complex are considered as the major detoxification mechanisms of As(V). In our study, the expression of RcAR increased in leaves and roots of As(V)-tolerant castor genotype WM but decreased in sensitive genotype GCH 2 due to 200 μM As(V) treatment. The activity of glutathione reductase (GR) increased significantly in the tolerant genotype, whereas it remained same in the sensitive genotype. GSH/GSSH ratio declined substantially in the sensitive genotype. The increased expression of phytochelatin synthase 1 isoform 1 (RcPCS1X1) in roots, RcPCS1X2 and metallothionein type 2 (RcMT2) in leaves, and c-type ABC transporter (RcABCC) in roots and leaves of WM was observed, but the expression of these genes declined or remained the same in GCH 2. Overall, our results suggest the essential roles of GR, RcAR, RcPCS1, RcMT2, and RcABCC in the tolerance of WM castor genotype to As(V) toxicity.

Agrobacterium tumefaciens GW4 is a heterotrophic arsenite-oxidizing bacterium with a high resistance to arsenic toxicity. It is now a model organism for studying the processes of arsenic detoxification and utilization. Previously, we demonstrated that under low-phosphate conditions, arsenate [As(V)] could enhance bacterial growth and be incorporated into biomolecules, including lipids. While the basic microbial As(V) resistance mechanisms have been characterized, global metabolic responses under low phosphate remain largely unknown. In the present work, the impacts of As(V) and low phosphate on intracellular metabolite and lipid profiles of GW4 were quantified using liquid chromatography-mass spectroscopy (LC-MS) in combination with transcriptional assays and the analysis of intracellular ATP and NADH levels. Metabolite profiling revealed that oxidative stress response pathways were altered and suggested an increase in DNA repair. Changes in metabolite levels in the tricarboxylic acid (TCA) cycle along with increased ATP are consistent with As(V)-enhanced growth of A. tumefaciens GW4. Lipidomics analysis revealed that most glycerophospholipids decreased in abundance when As(V) was available. However, several glycerolipid classes increased, an outcome that is consistent with maximizing growth via a phosphate-sparing phenotype. Differentially regulated lipids included phosphotidylcholine and lysophospholipids, which have not been previously reported in A. tumefaciens The metabolites and lipids identified in this study deepen our understanding of the interplay between phosphate and arsenate on chemical and metabolic levels. IMPORTANCE Arsenic is widespread in the environment and is one of the most ubiquitous environmental pollutants. Parodoxically, the growth of certain bacteria is enhanced by arsenic when phosphate is limited. Arsenate and phosphate are chemically similar, and this behavior is believed to represent a phosphate-sparing phenotype in which arsenate is used in place of phosphate in certain biomolecules. The research presented here uses a global approach to track metabolic changes in an environmentally relevant bacterium during exposure to arsenate when phosphate is low. Our findings are relevant for understanding the environmental fate of arsenic as well as how human-associated microbiomes respond to this common toxin., (Copyright © 2021 American Society for Microbiology.)

The adsorptive removal of a pollutant from water is significantly affected by the presence of coexisting ions with various concentrations. Here, we have studied adsorption of arsenate [As(V)] by calcined Mg-Fe-(CO 3 )-LDH in the presence of different cations (Mg 2+ , Na + , K + , Ca 2+ , and Fe 3+ ) and anions (CO 3 2‒ , Cl ‒ , PO 4 3‒ , SO 4 2‒ , and NO 3 ‒ ) with their different concentrations to simulate the field condition. The experimental results indicated that Ca 2+ , Mg 2+ , and Fe 3+ have a synergistic effect on removal efficiency of As(V), whereas PO 4 3‒ and CO 3 2‒ ions have a significant antagonistic impact. Overall, the order of inhibiting effect of coexisting anions on adsorption of As(V) was arrived as NO 3 - ˂Cl - 4 2- 3 2 - 4 3 - . Among them, competitive adsorption of phosphate with arsenic at different initial phosphate concentrations was found to be responsive to formulate a binary adsorption system. We have also developed a modified non-competitive Langmuir and Langmuir-Freundlich models; however, the modified competitive Langmuir model was arrived to be the most adequate model for this binary system. An Artificial Neural Network based multivariate prediction model was developed, delineating the impact of coexisting ions on the adsorption system. The proposed method may appropriately demonstrate the overall system and exhibited a significantly adequate prediction model with high R 2 , high F-value, and low error values.

The use of irrigation water containing arsenic (As) had led to large areas of As-contaminated farmland, and as a result, plants and food have become severely poisoned. Humic acid (HA) can be complexed with metals, which in turn affects the metals' behavior. Herein, we explored the accumulation of arsenate in lettuce treated with different concentrations of arsenate and studied the effects of HA on the accumulation and toxicity of arsenate. The addition of HA did not cause significant changes in the arsenate content in lettuce but had a significant effect on the activity of antioxidant enzymes, which improved the antioxidant capability of the lettuce plants. Furthermore, HA promoted the accumulation of nutrients, such as magnesium (Mg), calcium (Ca), molybdenum (Mo) and manganese (Mn), in the leaves. Arsenate disrupted metabolic pathways, such as amino acid metabolism, carbohydrate metabolism, and aminoacyl-tRNA biosynthesis. The addition of HA increased the contents of amino acids and sugars, thereby improving lettuce growth. The present study explored the effects of HA on As accumulation and related physiological changes (antioxidant enzyme activities, absorption of nutrients and metabolic mechanisms) and provided insights into the regulation of As contamination by HA, which is relatively inexpensive., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Anaeromyxobacter sp. strain PSR-1, a dissimilatory arsenate [As(V)]-reducing bacterium, can utilize As(V) as a terminal electron acceptor for anaerobic respiration. A previous draft genome analysis revealed that strain PSR-1 lacks typical respiratory As(V) reductase genes ( arrAB ), which suggested the involvement of another protein in As(V) respiration. Dissimilatory As(V) reductase activity of strain PSR-1 was induced under As(V)-respiring conditions and was localized predominantly in the periplasmic fraction. The activity was visualized by partially denaturing gel electrophoresis, and liquid chromatography-tandem mass spectrometry analysis identified proteins involved in the active band. Among these proteins, a protein annotated as molybdopterin-dependent oxidoreductase (PSR1_00330) exhibited the highest sequence coverage, 76%. Phylogenetic analysis revealed that this protein was a homolog of tetrathionate reductase catalytic subunit TtrA. However, the crude extract of strain PSR-1 did not show significant tetrathionate reductase enzyme activity. Comparative proteomic analysis revealed that the protein PSR1_00330 and a homolog of tetrathionate reductase electron transfer subunit TtrB (PSR1_00329) were expressed abundantly and specifically under As(V)-respiring conditions, respectively. The genes encoding PSR1_00330 and PSR1_00329 formed an operon-like structure along with a gene encoding a c -type cytochrome ( cyt c ), and their transcription was upregulated under As(V)-respiring conditions. These results suggest that the protein PSR1_00330, which lacks tetrathionate reductase activity, functions as a dissimilatory As(V) reductase in strain PSR-1. Considering the wide distribution of TtrA homologs among bacteria and archaea, they may play a hitherto unknown role along with conventional respiratory As(V) reductase (Arr) in the biogeochemical cycling of arsenic in nature. IMPORTANCE Dissimilatory As(V)-reducing prokaryotes play significant roles in arsenic release and contamination in groundwater and threaten the health of people worldwide. Generally, such prokaryotes reduce As(V) by means of a respiratory As(V) reductase designated Arr. However, some dissimilatory As(V)-reducing prokaryotes such as Anaeromyxobacter sp. strain PSR-1 lack genes encoding Arr, suggesting the involvement of other protein in As(V) reduction. In this study, using multiple proteomic and transcriptional analyses, it was found that the dissimilatory As(V) reductase of strain PSR-1 was a protein closely related to the tetrathionate reductase catalytic subunit (TtrA). Tetrathionate reductase is known to play a role in anaerobic respiration of Salmonella on tetrathionate, but strain PSR-1 showed neither growth on tetrathionate nor significant tetrathionate reductase enzyme activity. These results suggest the possibility that TtrA homologs encoded in a wide variety of archaeal and bacterial genomes might function as dissimilatory As(V) reductases., (Copyright © 2020 American Society for Microbiology.)

Contamination of soil and water with heavy metals and metalloids is a serious environmental problem. Cadmium and arsenic are major environmental contaminants that pose a serious threat to human health. Although toxicities of cadmium and arsenic to living organisms have been extensively studied, the molecular mechanisms of cellular responses to cadmium and arsenic remain poorly understood. In this study, we demonstrate that the cell wall integrity (CWI) pathway is involved in coping with cell wall stresses induced by cadmium and arsenate through its role in the regulation of cell wall modification. Interestingly, the Rlm1p and SBF (Swi4p-Swi6p) complex transcription factors of the CWI pathway were shown to be specifically required for tolerance to cadmium and arsenate, respectively. Furthermore, we found the PIR2 gene, encoding cell wall O-mannosylated heat shock protein, whose expression is under the control of the CWI pathway, is important for maintaining cell wall integrity during cadmium and arsenate stresses. In addition, our results revealed that the CWI pathway is involved in modulating the expression of genes involved in cell wall biosynthesis and cell cycle control in response to cadmium and arsenate via distinct sets of transcriptional regulators. IMPORTANCE Environmental pollution by metal/metalloids such as cadmium and arsenic has become a serious problem in many countries, especially in developing countries. This study shows that in the yeast S. cerevisiae , the CWI pathway plays a protective role against cadmium and arsenate through the upregulation of genes involved in cell wall biosynthesis and cell cycle control, possibly in order to modulate cell wall reconstruction and cell cycle phase transition, respectively. These data provide insights into molecular mechanisms underlying adaptive responses to cadmium and arsenate., (Copyright © 2020 American Society for Microbiology.)

We constructed consortia of Chlorella salina and Bacillus subtilis with various alga-bacterium ratios (1:0, 1:1, 1:2, 1:3, 1:4). After being treated with arsenate [As(Ⅴ)] for 7 d, we measured the growth, As accumulation, adsorption and absorption, and As speciation transformation of consortia. Results showed that the chlorophyll content, dry weight, and specific growth rate of the symbiont increased significantly with increasing B. subtilis ratio after the As(Ⅴ) treatment, being 1.81 mg·L -1 , 125.0 mg, and 0.28 mg·L -1 ·d -1 under the condition of the alga-bacterium ratio being 1∶4 and As(Ⅴ) being 750 μg·L -1 , respectively. The accumulation and absorption of As by the consortia decreased with the bacterial proportion increasing from 1:0 to 1:4. As accumulation changed with the As concentration, with a dominance of absorption under 75-150 μg·L -1 As(Ⅴ) and a dominance of adsorption under 300-750 μg·L -1 As(V). There were As(Ⅴ) and As(Ⅲ) in the consortia. When the proportion of bacteria increased, the rate of As(Ⅴ) reduction enhanced (up to 12.6%). Our results indicated that the increases of B. subtilis improved As(Ⅴ) tolerance and reduction, but decreased the As(Ⅴ) accumulation by the symbiont.

Influence of arsenic (As) in As tolerant and sensitive rice genotypes based chloroplastic pigments, leaf gas exchange attributes and their influence on carbohydrate metabolism were investigated in the present study. As retards growth of crop plants and increase several health ailments by contaminating food chain. Photosynthetic inhibition is known to be the prime target of As toxicity due to over-production of ROS. Hydroponically grown rice seedlings of twelve cultivars were exposed to 25, 50, and 75 μM arsenate (AsV) that exerted negative impact on plastidial pigments content and resulted into inhibition of Hill activity. Internal CO 2 concentration lowered gradually due to interference of As with stomatal conductance and transpiration rate that subsequently led to drop in net photosynthesis. Twelve contrasting rice genotypes responded differentially to As(V) stress. Present study evaluated As tolerant and sensitive rice cultivars with respect to As(V) imposed alterations in pigments content, photosynthetic attributes along with sugar metabolism. Starch contents, the principle carbohydrate storage declined differentially among As(V) stressed test cultivars, being more pronounced in cvs. Swarnadhan, Tulaipanji, Pusa basmati, Badshabhog, Tulsibhog and IR-20 compared to cvs. Bhutmuri, Kumargore, Binni, Vijaya, TN-1 and IR-64. Therefore, the six former cultivars tried to adapt defensive mechanisms by accumulating higher levels of reducing and non-reducing sugars to carry out basal metabolism to withstand As(V) induced alterations in photosynthesis. This study could help to screen As tolerant and sensitive rice genotypes based on their photosynthetic efficiency in As polluted agricultural fields to reduce As contamination assisted ecotoxicological risk.

Phosphate competes with arsenate for sorption sites on poorly crystalline iron and aluminum (hydr)oxides. The competition has implications e.g. for the management of arsenic-contaminated soil and water. Phosphate competition with arsenate on mixed phases containing both iron and aluminum (hydr)oxides has rarely been investigated. Here, the phosphate competition with arsenate on mixtures of poorly crystalline aluminum hydroxide (Alhox) and ferrihydrite (Fh), was investigated in batch experiments at pH 6.5. X-ray absorption spectroscopy (XAS) was performed on the phosphorus and arsenic K edges, which offered a unique insight in the partitioning of arsenate and phosphate on mixed Alhox-Fh sorbents. Under the studied conditions the sorption capacity of the mixed sorbents (per mol Al or Fe) increased at higher Alhox to Fh ratios. The XAS measurements provided direct evidence that phosphate competed more effectively with arsenate for sorption sites on Alhox than on Fh. For example, in a mixture with 50% of both sorbents and with similar additions of arsenate and phosphate, 71% of the oxyanions adsorbed on Fh and 46% on Alhox were arsenate. Consequently, phosphate may mobilize arsenate more easily from mixed iron-aluminum matrices that are rich in aluminum., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The covalent organic framework (COF) is made light elements linked by covalent networks. This study synthesize and characterized, and for the first time applied the produced EB-COF:Br as adsorbent for phosphate and arsenate removal from nearly neutral waters. The synthesized COF was first proven structurally stable in solutions of 75% H 3 PO 4 , 6 M HCl, or 6 M NaOH. Then the phosphate adsorption onto the EB-COF:Br was shown to be an endothermic process with maximum adsorption capacity at 25, 35 and 45 °C as 25.3, 34.7 and 35.3 mg/g COF, respectively; and the corresponding arsenate adsorption process being an exothermic process with maximnum adsorption capacity as 53.1, 27.5 and 5.1 mg/g, respectively. The synthesized COF could also effectively adsorb phosphate and arsenate ions from river water (pH 7.45) but at reduced adsorption capacities. The electrostatic interactions between the negative charge on phosphate or arsenate ions and the positively charged (N + -) of COF, and the hydrogen bondings between H atom on phosphate or arsenate ions and the (-CO) group of COF were the dominating mechanisms for the present adsorption process. The strong electrostatic interactions for arsenate contributed to its higer adsorption capacity than noted for phosphate at 25 °C. However, the disturbed hydrogen bonding induced by mismatched sizes of arsenate ion and the adsorption sites surrounded by the (N + -) and the (-CO) groups reduced the stability of arsenate to against temperature and external anion challenges. The use of the EB-COF; Br as industrial adsorbent was also discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The toxicity of arsenic (As) has been reported to be different depending on their chemical forms. However, its toxicity mechanisms largely remain unknown. In this study, to investigate toxicity mechanism of As in marine zooplanktons, namely, the rotifer Brachionus plicatilis and the copepod Paracyclopina nana, metabolites of As were analyzed by using a high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry with in vivo toxicity and antioxidant responses in response to inorganic As, including arsenate (As V ) and arsenite (As III ). While As III was more toxic than As V in both organisms, the rotifer B. plicatilis exhibited stronger tolerance, compared to the copepod P. nana. The As speciation analysis revealed differences in biotransformation processes in two species with B. plicatilis having a more simplified process than P. nana, contributing to a better tolerance against As in the rotifer B. plicatilis compared to P. nana. Moreover, the levels of GSH content and the regulation of omega class glutathione S-transferases were different in response to oxidative stress between B. plicatilis and P. nana. These results suggest that the rotifer B. plicatilis has a unique survival strategy with more efficient biotransformation and antioxidant responses, compared to P. nana, conferring higher tolerance to As., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Aqueous arsenate [As(V)] was removed using an aluminum-based adsorbent (ABA) and coal mine drainage sludge coated polyurethane (CMDS-PU) prepared using alum and coal mine sludge, respectively. Their As(V) removal efficiencies were compared with each other and granular ferric hydroxide (GFH). The mineralogy and surface chemistry of materials were determined using wavelength dispersive X-ray fluorescence (WD XRF) and Fourier transform infrared spectroscopy (FTIR), respectively. The angle-resolved X-ray photoelectron spectroscopy (AR-XPS) studies confirmed As(V) retention on the adsorbent surfaces. The adsorption kinetics data were fitted to pseudo second-order rate equation. The faster As(V) uptake kinetics of GFH and ABA (GFH > ABA > CMDS-PU) were attributed to their large pore volume and mesoporous nature. Langmuir adsorption capacities of 22, 31 and 10 mg/g, were achieved for GFH, ABA and CMDS-PU, respectively. As(V) adsorption on GFH, ABA and CMDS-PU was endothermic. GFH and ABA were efficient over a wide pH range (3-10). In column studies, GFH, ABA, and CMDS-PU successfully treated 23625, 842, and 158 bed volumes (BVs) and 2094, 6400, and 17 BVs of As(V)-contaminated water with 9.5 and 27 EBCT, respectively (at pH = 6.0, As i  = 600 μg/L). The GFH and ABA have a potential to be used at large-scale aqueous phase As(V) remediation., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

This study aims to illustrate the preparation of a new nanobiocomposite by incorporating copper oxide nanoparticles into cuttlebone matrix (CB/CuO NPs), and it was tested to define how effective it was to adsorb and remove arsenate from aqueous systems. CB is the bone tissue of cuttlefish with high porosity, permeability, and low cost. CuO NPs have been introduced as an effective arsenate adsorbent. Producing nanocomposite by introducing of CuO NPs in the structure of CB enhanced their stability and facilitated their separation from solution. Incorporation of CuO NPs in the structure of CB enhanced the adsorption capacity of CB. The adsorption data were fitted with both Langmuir and Freundlich isotherms, but Langmuir isotherm exhibited better matching rather than Freundlich isotherm. The maximum adsorption capacity (q max ) was calculated from Langmuir adsorption isotherm which was around 25.13 mg g -1 . Kinetic data fitted well to the pseudo-second-order reaction model. The results indicate that the possible mechanism of arsenate adsorption on CB/CuO is through development of inner sphere complex. Simple preparation and abundant and good adsorption capacity in the presence of calcium ions indicate that the CB/CuO is suitable for removal of arsenate from contaminated drinking water.

Only limited information is available on the effects of dissolved organic phosphorus (DOP) on arsenate (As(V)) bioaccumulation and biotransformation in organisms. In this study, we examined the influence of three different DOP forms (β-sodium glycerophosphate (βP), adenosine 5'-triphosphate (ATP), and D-Glucose-6-phosphate disodium (GP) salts) and inorganic phosphate (IP) on As(V) toxicity, accumulation, and biotransformation in Microcystis aeruginosa. Results showed that M. aeruginosa utilized the three DOP forms to sustain its growth. At a subcellular level, the higher phosphorus (P) distribution in metal-sensitive fractions (MSF) observed in the IP treatments could explain the comparatively lower toxic stress of algae compared to the DOP treatments. Meanwhile, the higher MSF distribution of arsenic (As) in M. aeruginosa in the presence of DOP could explain the higher toxicity with lower 96-h half maximal effective concentration (EC 50 ) values. Although we observed As(V) and P discrimination in M. aeruginosa under IP treatments with high intracellular P/As, we did not find this discrimination under the DOP treatments. As accumulation in algal cells was therefore greatly enhanced by DOP, especially βP, given its lower transformation rate to phosphate compared to ATP and GP in media. Additionally, As(V) reduction and, subsequently, As(III) methylation were greatly facilitated in M. aeruginosa by the presence of DOP, particularly GP, which was confirmed by the higher relative expression of its two functional genes (arsC and arsM). Our findings indicate that As(V) accumulation and its subsequent biotransformation were enhanced by organic P forms, which provides new insight into how DOP modulates As metabolism in algae., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Arsenic-containing water poses a serious threat to human health. In this study, two types of Fe-modified rice straw biochars [(Fe-impregnated biochar (FeIm char) and pre-modified rice straw biochar (PMRS char)] were prepared, in which three ratios [1, 5, and 10% (w/w)] of Fe modification were evaluated, resulting in six different Fe-modified biochars. Then, a series of adsorption experiments, using single- and binary-metal solutions of As(V) and Cd(II), were conducted to investigate the performances of modified biochars on metal adsorption compared to pristine rice straw biochar (RS char). Results indicated Fe modification improved the As(V) adsorption capacity of biochar. PMRS char showed higher adsorption of As(V) than FeIm char. At the 5% Fe modification ratio (FMR), the As(V) removal by PMRS char (at 10 g/L dosage) from 100 mg/L As(V) solution was approximately 69.6%, which was higher than 46.1% of FeIm char or 22.6% of RS char. In contrast, the adsorption of Cd(II) was decreased after modified at 5 or 10% FMR. Interestingly, for treating solution containing As(V) and Cd(II) together, the adsorption of As(V) onto FeIm char or PMRS char prepared at 5 or 10% FMR remained higher than that onto RS char, while the simultaneous removal of Cd(II) ion by either modified biochar was kept over 50%. Thus, the finding of this study suggested Fe-modified biochars, especially prepared via the pyrolysis of FeCl 3 pre-soaking rice straw, could be a promising adsorbent for the remediation of complex As(V)-containing wastewater.

As a problematic element in water systems, arsenic exists as As(III) and As(V). Adsorption techniques can be used to remove anionic As(V) as it is present as a polyatomic anion. In the case of As(III) which exists in zero-valent state under neutral pH, it can be also removed by adsorption after being converted into As(V). Many inorganic and organic materials have been examined as potential adsorbents for anionic As(V) removal. However, most exhibit relatively low adsorption capacities (<10 mg/g). The objective of this study is to examine As(V)-removal mechanism and practical potential of a PEI-coated bacterial biosorbent prepared from fermentation biowaste. The maximum As(V) uptake of the biosorbent was determined to be 62.99 mg/g by Langmuir model. The effects of various parameters including pH, biosorbent dosage, ionic strength and temperature were also examined. Kinetic and equilibrium models were used to interpret the experimental data mathematically. A 0.01 M NaOH solution was chosen as an effective As(V)-desorbing eluent for biosorbent regeneration. The adsorption capacity of the biosorbent remained above 85% over three successive cycles of adsorption and desorption. In conclusion, the biowaste-driven biosorbent is a promising anion adsorbent for treatment of As(V)-contaminated wasters., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The sequential application of a polymer inclusion membrane (PIM), composed of poly(vinylidenefluoride-co-hexafluoropropylene) and the anionic extractant Aliquat 336, and a microporous polytetrafluoroethylene (PTFE) gas-permeable membrane was utilized for the first time to develop a flow analysis (FA) system, for the automatic determination of trace levels of arsenate (As(V)) in drinking water as arsine. The system incorporated a flow-through extraction cell for separation and preconcentration of arsenate and a gas-diffusion cell for the separation of arsine prior to its spectrophotometric determination based on the discoloration of a potassium permanganate solution. Under optimal conditions the FA system is characterized by a limit of detection of 3.0 μg L -1 As(V) and repeatability of 1.8% (n = 5, 25 μg L -1 As(V)) and 2.8% (n = 5, 50 μg L -1 As(V)). The newly developed FA method was successfully applied to the determination of arsenate in drinking water samples in the μg L -1 concentration range., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

TiO 2 is one of the most cheap materials which can both adsorb arsenic and oxidize arsenite [As(III)] to arsenate [As(V)]. In this study, anatase TiO 2 crystals with different main facets such as {101}, {001} and {100} are synthesized and used to investigate arsenic adsorption kinetics, adsorption isotherms, photocatalytic oxidation (PCO) process and the pH effects. The adsorption kinetics of arsenic on TiO 2 crystals can be described by the pseudo second-order kinetic model. For the adsorption isotherms, the Langmuir model is better than the Freundlich model for arsenic on these TiO 2 crystals. For the PCO process, the rate of As(III) oxidation can be denoted by the pseudo first-order kinetic model. It should be noted that at neutral condition the adsorption and PCO rates of the three kinds of TiO 2 crystals follow the order of {101} > {001} > {100}. The pH effect is above all important for both the arsenic adsorption and its PCO. The highest PCO speed appears at high pH values such as at pH 11 or 12., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Prenatal exposure to arsenic, a naturally occurring toxic element, causes neural tube defects (NTDs) and, in animal models, orofacial anomalies. Since aberrant development or migration of cranial neural crest cells (CNCCs) can also cause similar anomalies within developing embryos, we examined the effects of in utero exposure to sodium arsenate on gene expression patterns in pure populations of CNCCs, isolated by fluorescence activated cell sorting (FACS), from Cre/LoxP reporter mice. Changes in gene expression were analyzed using Affymetrix GeneChip ® microarrays and expression of selected genes was verified by TaqMan quantitative real-time PCR. We report, for the first time, arsenate-induced alterations in the expression of a number of novel candidate genes and canonical cascades that may contribute to the pathogenesis of orofacial defects. Ingenuity Pathway and NIH-DAVID analyses revealed cellular response pathways, biological themes, and potential upstream regulators, that may underlie altered fetal programming of arsenate exposed CNCCs., (Copyright © 2019 Elsevier Inc. All rights reserved.)

p-Arsanilic acid (p-ASA) and roxarsone (ROX) are two major phenylarsenic feed additives that are still widely used in many countries, and the land application of animal waste containing these compounds could introduce large quantities of arsenic into the environment. In this study, we proposed a treatment scheme for animal waste that involves leaching of p-ASA/ROX out of the manure first by water, then oxidation by ferrate (Fe(VI)) and removal of the arsenate released by in situ formed Fe(III) oxide-hydroxide. The effects of solution pH, dosage of Fe(VI), solution ionic strength, and matrix species on the treatment performance were systematically evaluated. Initial solution pH values of 4.1 and 2.0 were chosen for the oxidation of p-ASA and ROX, respectively, while efficient arsenate removal could be achieved with relatively small adjustment of the final solution pH (to 4.0). The pH-dependent second-order rate constants for the reactions between ferrate and p-ASA and ROX over the pH range of 2.0-12.0 were estimated to be 7.13 × 10 5 -2.01 × 10 -1 and 8.91 × 10 3 -1.65 × 10 -1  M -1  s -1 , respectively. The degradation pathways of p-ASA/ROX during ferrate oxidation were proposed based on the inorganic and organic intermediates identified. Depending on the levels of p-ASA/ROX, effective treatment could be achieved through flexible adjustment of the Fe(VI) dosage. p-ASA/ROX (10 mg-As/L) in swine manure leachate could be efficiently treated by ferrate oxidation within 5 min, with the overall arsenic removal efficiency higher than 99.2%. The treatment performance was barely affected by the presence of common ions (K + , Ca 2+ , Na + , Mg 2+ , SO 4 2- , NO 3 - , and Cl - ), while humic acid, Mn 2+ , Ni 2+ , Fe 3+ , and Co 2+ inhibited p-ASA/ROX oxidation. The presence of PO 4 and humic acid compromised sorptive removal of the released arsenate due to their competitive sorption on the Fe(III) oxide-hydroxide precipitate. Ferrate oxidation is green and fast, and the operation is simple, thus it could serve as a promising and environment-friendly option for mitigating the risk of phenylarsenic feed additives in animal waste.3- and NH 4 + could accelerate the oxidation of p-ASA/ROX, but PO 4 3- and humic acid compromised sorptive removal of the released arsenate due to their competitive sorption on the Fe(III) oxide-hydroxide precipitate. Ferrate oxidation is green and fast, and the operation is simple, thus it could serve as a promising and environment-friendly option for mitigating the risk of phenylarsenic feed additives in animal waste., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

In this work, zinc ferrite spinel with different zinc contents (Zn x Fe 3-x O 4 ) was synthesized by a hydrothermal method and used for removing As(V) in aqueous solution. X-ray diffraction (XRD) results indicated that in the crystal structure of Zn x Fe 3-x O 4 , the zinc atoms tended to occupy the octahedral sites for x < 0.6 and diffused into the tetrahedral sites gradually with x > 0.6. The size of Zn x Fe 3-x O 4 crystallites increased with the increasing zinc content. Batch adsorption experiments showed that the adsorption isotherms could be well described by the Langmuir model, while the adsorption kinetics followed the pseudo-second-order kinetic model. Zinc ferrite exhibited the highest adsorption capacity towards As(V) when x = 0.6. Study of the mechanism indicated that doping with zinc increased the number of surface hydroxyl groups on ferrite spinel, and thus enhanced the adsorption capacity when x = 0.6. This work revealed the effects of doping site and content of metal atoms on the adsorption ability of ferrite spinel towards As(V)., (Copyright © 2018. Published by Elsevier B.V.)

Arsenic (As) contamination in agricultural soil can cause phytotoxicity and lead to As accumulation in crops. Rice (Oryza sativa) feeds half of the world's population, but the molecular mechanism of As detoxification is not well understood in rice. In this study, the role of OsNLA1 in arsenate uptake and tolerance in rice was analyzed. OsNLA1 expression was induced in response to As(V) stress. The osnla1 mutant was more sensitive to As(V) stress than those of the wild type (WT). When exposed to As(V), mutation of OsNLA1 resulted in 30% greater As accumulation in roots and shoots of the WT. Although OsPT8 expression was induced after As(V) exposure, the amount of its protein was reduced. Unexpectedly, the osnla1 mutant showed a significant increase in punctate structures of OsPT8-GFP in response to As(V) stress, while the amount of the OsPT8-GFP protein in the osnla1 mutant was greater than in the WT. Combining OsNLA1 mutation with OsPT8 overexpression resulted in As(V) hypersensitivity, As hyperaccumulation, and higher shoot to root ratio of As in rice. These results indicated that OsNLA1 plays an important role in arsenate uptake and tolerance, mainly via regulating the amount of Pi transporters., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

In this study, Mn-doped MgAl-layered double hydroxides (LDHs) were successfully synthesized for efficient removal arsenate from aqueous solution. The structure and composition of Mn-doped MgAl-LDHs intercalated by different ions such as CO 3 2- , Cl - , or NO 3 adsorption-desorption presented that the Mn-doped MgAl-LDHs (donated as Mn-LDHs) have very similar physical morphologies and properties to the MgAl-Cl-LDHs (donated as Mg-LDHs). However, the Mn-LDHs exhibits more preferable arsenate adsorption than Mg-LDHs. The As(V) removal kinetics data of Mn-LDHs is followed pseudo-second-order expression. The adsorption capacity of As(V) on Mn-LDHs via Langmuir isotherm model was 166.94 mg g - were investigated. The characterizations of XRD, ATR FT-IR, SEM, TG-DTA, and N 2 adsorption-desorption presented that the Mn-doped MgAl-LDHs (donated as Mn-LDHs) have very similar physical morphologies and properties to the MgAl-Cl-LDHs (donated as Mg-LDHs). However, the Mn-LDHs exhibits more preferable arsenate adsorption than Mg-LDHs. The As(V) removal kinetics data of Mn-LDHs is followed pseudo-second-order expression. The adsorption capacity of As(V) on Mn-LDHs via Langmuir isotherm model was 166.94 mg g -1 . The results of XPS revealed that the enhanced removal mechanism can be attributed to surface complexation of As(V) with Mn on the surface of Mn-LDHs. These results prove that Mn-doped LDHs can be considered as a potential material for adsorption As(V) from wastewater.

High levels of inorganic arsenic (iAs) exposure are associated with severe health effects. Less clear are effects of lower exposure levels on neurodevelopment. Relative to maternal intake, there is limited lactational transfer of arsenic in humans or rodents, yet there are few rodent studies which directly exposed preweaning animals. To more clearly determine iAs developmental neurotoxicity, 28 pregnant Sprague-Dawley rats were exposed to arsenate (AsV) via drinking water (0, 23.6, 47.7, 71.0 ppm) (n = 5-7/group) from gestational day (GD) 6 through GD 22 with targeted doses of 0, 2.33, 4.67, 7.00 mg/kg/day, respectively. Offspring were dosed by gavage daily with the same mg/kg AsV dose as intended for their dam from postnatal day (PND) 1 to 21. Gestational water intake was reduced at all AsV doses, but returned to control levels on lactational day (LD) 1 when control water was returned. Gestational body weight was reduced only at the highest dose on GD 22 and lactational body weight was unaffected. Food intake was unaffected. iAs exposure did not alter offspring body weight (PNDs 1-21) or age at fur development and bilateral ear opening. Incisor eruption, however, was significantly delayed in offspring of the 4.67 and 7.00 mg/kg groups. Further, all iAs groups were significantly delayed in bilateral eye opening. Righting reflex (PNDs 3-6) was unaffected, while slant board performance (PNDs 8-11) was significantly poorer at the highest dose. Brains of culled pups (PND 1) showed dose-dependent increases of iAs. There were no significant AsV-related effects on PND 21 brain regional concentrations of dopamine, DOPAC, HVA, 5-HT or 5-HIAA. These hazard identification results will guide the study designs of developmental iAs exposure at human-relevant levels essential for risk-assessment., (Published by Elsevier Inc.)

This paper reports a simple, facile and rapid preparation of 3‑mercapto‑propanoic acid (MPA) modified cellulose filter paper (MPA-Cell paper) for arsenate removal from drinking water. The MPA was covalently grafted to the cellulose filter paper (Cell) by esterification process through the formation of O‑acylisourea intermediate and characterized by the FTIR, SEM, EDS and XPS analyses. The arsenate adsorption efficiency was studied for batch and semi-continuous systems while exploring the adsorption kinetics, isotherm and the effect of pH for the former. The experimental data fitted well with Langmuir, Dubinin-Radushkevich (DR) and pseudo second order kinetic models. The mechanism of adsorption was studied by FTIR spectroscopy utilizing the adsorption isotherm, kinetic model and XPS results. The modified filter paper performed well at nearly neutral pH in arsenate removal through adsorption and demonstrated a significant arsenate uptake capacity of 92.59 mg/g. The DR and FTIR results indicated that the adsorption of arsenate ion occurred through ion exchange process. The MPA-Cell paper could have a potential use as low-cost but efficient commercial adsorbent for arsenate abatement from contaminated drinking water by both batch as well as semi-continuous operating systems. The MPA-Cell paper could purify ground water containing high level of arsenate., (Copyright © 2018. Published by Elsevier B.V.)

Nitric oxide (NO) and reactive oxygen species (ROS) are important signaling molecules regulating development of plants. However under metal stress, in developmental processes of plants their implications are not largely known. Therefore, in the present study, role of NO and ROS crosstalk in the regulation of formation of new adventitious roots (NARs) and primary root biomass accumulation (PRBA) has been investigated in rice seedlings under arsenate (As V ) stress. Addition of sodium nitroprusside (SNP, a donor of NO) induced formation of NARs, increased PRBA, and maintained the redox status of ascorbate and cell cycle dynamics. However, addition of NG-nitro-l-arginine methyl ester (L-NAME, an inhibitor of nitric oxide synthase) and 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO, a NO scavenger) either in presence of SNP or in its absence blocked formation of NARs and reduced PRBA. Further, to decipher crosstalk of NO and ROS, we used diphenylene iodonium (DPI, an inhibitor of NADPH oxidase), and even in presence of SNP it blocked formation of NARs which indicate that ROS are also essential for formation of NARs. Further a connection of NO-ROS signaling with the redox status of ascorbate and the cell cycle dynamics, governing formation of NARs and PRBA in rice seedlings under As V stress is discussed., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Manganese dioxide (MnO 2 ) synthesized by solid-state reaction was characterized and sorption of As(III) and As(V) on it was studied in batch mode using 76 As radiotracer. Arsenic removal efficiency was ∼98 % in the pH range of 3-9. Solvent extraction study indicated that >95% of arsenic is present as As(V) after sorption. A new electrochemical method was developed for explaining the arsenic-manganese interactions. Cyclic voltammetry and chronopotentiometry measurements were carried out which indicated the difference in the interaction of As(III) and As(V) with MnO 2 . X-ray Photoelectron Spectroscopy (XPS) was carried out in which the 3p 3/2 binding energy peak of As(III) and As(V) standards was compared with the binding energy peaks observed for arsenic sorbed on manganese dioxide. The binding energy peaks of arsenic on MnO 2 were matching with that of As(V), irrespective of the oxidation state of arsenic taken for sorption. The study confirmed that irrespective of the initial oxidation state, arsenic was sorbed on MnO 2 as As(V); during the oxidation of As(III) by MnO 2 , manganese was reduced to Mn(II) and the Mn(II) formed during sorption was sorbed on the surface creating fresh surface promoting further sorption. Based on the observations, a mechanism of sorption has been proposed.

The modification of the fly ash (FA) by magnetite (M) was performed to obtain FAM adsorbent with improved adsorption efficiency for arsenate removal from water. The novel low cost adsorbents are characterized by liquid nitrogen porosimetry (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD), Mössbauer spectroscopy (MB) and Fourier transform infrared (FTIR) spectroscopy. The optimal conditions and key factors influencing the adsorbent synthesis are assessed using the response surface method (RSM). The adsorption experiment was carried out in a batch system by varying the contact time, temperature, pH, and mass of the adsorbent. The adsorption capacity of the FAM adsorbent for As(V), calculated by Langmuir model, was 19.14 mg g -1 . The thermodynamic parameters showed spontaneity of adsorption with low endothermic character. The kinetic data followed the pseudo-second-order kinetic model (PSO), and Weber-Morris model indicated intra-particle diffusion as rate limiting step. Alternative to low desorption capability of the FAM was found by five consecutive adsorption/magnetite precipitation processes which gave exhausted layered adsorbent with 65.78 mg g -1 capacity. This research also has shed light on the mechanism of As(V)-ion adsorption, presenting a promising solution for the valorization of a widely abundant industrial waste., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In the eukaryotic model yeast Saccharomyces cerevisiae, arsenic (As) detoxification is regulated by two transcriptional factors, Yap8 and Yap1. Yap8 specifically controls As extrusion from the cell, whether Yap1 avoids arsenic-induced oxidative damages. Accordingly, cells lacking both Yap1 and Yap8 are more sensitive to arsenate than cells lacking each regulator individually. Strikingly enough, the same sensitivity pattern was observed under anoxia, suggesting that Yap1 role in As detoxification might not be restricted to the regulation of the oxidative stress response. This finding prompted us to study the transcriptomic profile of wild-type and yap1 mutant cells exposed to arsenate. Interestingly, we found that, under such conditions, several genes involved in the biogenesis of FeS proteins were upregulated in a Yap1-dependent way. In line with this observation, arsenate treatment decreases the activity of the mitochondrial aconitase, Aco1, an FeS cluster-containing enzyme, this effect being even more pronounced in the yap1 mutant. Reinforcing the relevance of FeS cluster biogenesis in arsenate detoxification, the overexpression of several ISC and CIA machinery genes alleviates the deleterious effect of arsenate caused by the absence of Yap1 and Yap8. Altogether our data suggest that the upregulation of FeS biogenesis genes regulated by Yap1 might work as a cellular shield against arsenate toxicity., (Copyright © 2018. Published by Elsevier B.V.)

Arsenate and phosphate have similar properties due to their electrochemical structures, but their environmental impacts are unique. The abundance and competition of arsenate and phosphate determine their bioavailability and leachability; thus, it is essential to understand their fate in the soil environment. In this study, the effects of pH and surface loading on the competitive adsorption of arsenate and phosphate on four iron (hydr)oxides were evaluated by employing the Langmuir isotherm, competitive sorption ratio (CSR), and competition effect (CE). The stability and transformation of the iron (hydr)oxides were also assessed. Various adsorption patterns were observed in the single and mixed treatments by controlling the addition of oxyanions, pH, surface loading, and type of iron (hydr)oxides. Arsenate was preferentially adsorbed at a low pH, whereas phosphate showed the opposite trend. The CE As(V),P(V) was close to zero at low surface density (no competition) and sequentially changed to negative or positive values with increasing surface density, indirectly indicating the sequential development of promotive and competitive effects. Transformation in goethite was identified at a high pH with the presence of oxyanions, except that no transformation was observed upon the addition of oxyanions and with pH change. However, the stability of the iron (hydr)oxides decreased at a low pH and with the presence of phosphate, arsenate, or both. The hematite showed a significant promotive effect regardless of the pH. Our study revealed that the pH, surface loading, and type of iron (hydr)oxides are intercorrelated and simultaneously affect the adsorption characteristics of oxyanions and the stability of iron (hydr)oxides.

Arsenic (As) is a ubiquitous metalloid and toxic to plants. Chemical similarity between arsenate and phosphate (P) indicates possible antagonism between them in uptake and transportation. However, there is little study to reveal the interaction of As and P at transcriptional level. In this study RNA-sequencing was conducted on the two barley genotypes differing in As tolerance. A total of 2942 differentially expressed genes (DEGs) were inclusively expressed in both genotypes under As (100 μM) and As (100 μM) + P (50 μM), and these DEGs included hormonal signaling, stress responsive, transport related and transcription factors. P addition in the culture solution inhibited the KEGG pathways related to ABC transporters, ether lipid metabolism, linolenic acid metabolism, endocytosis and RNA transport. ZDB160 had a higher expression of DEGs associated with hormone signaling, secondary metabolites and stress defense under P conditions compared to ZDB475, which might explain its tolerance mechanism to As under P condition. The abscisic acid, jasmonic acid and salicylic acid signaling pathways were also significantly regulated under As + P conditions, which may also account for genotypic differences. Finally we drew up a hypothetical model of high As + P stress tolerance mechanism in ZDB160. It may be concluded that ZDB160 achieves its tolerance to As under P by up-regulating P transporters, resulting in more P uptake and less As translocation. The identified candidate genes related to As + P tolerance may provide insights into understanding As tolerance under limited P conditions., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

The treatment of the geothermal water discharged through mining activity is a critical issue because the rate of discharge is 12,000 m 3 per day and the discharge contains high concentrations of borate (>20 mg/L) and arsenate (ca. 0.4 mg/L) as well as silicate and carbonate. The simultaneous reduction of borate and arsenate concentrations to acceptable levels was successfully performed by co-precipitation with hydroxyapatite (HAp). Although the coexisting high concentrations of carbonate act as a disturbing element, the co-precipitation equilibrium of borate was shifted to lower values by adjusting the P/Ca molar ratio, and the removal rate of borate was accelerated by using Al 3+ additives, resulting in the efficient reduction of borate within 1 h. The initially immobilized boron in HAp is in the tetragonal form, which probably occupies the hydroxyl sites in HAp, gradually transforming into the trigonal form in the solid state, as interpreted by 1 H NMR and 11 B-NMR. The coexisting silicate was also immobilized in an ellestadite form, as confirmed by 29 Si-NMR measurements. Arsenate and silicate were immobilized before borate in geothermal water. A dissolution assay of borate in the solid residues after co-precipitation with HAp verified the acceptable stability of borate, which is independent of the amount of added Al 3+ ., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Arsenic (As) is a ubiquitous metalloid and a health hazard to millions of people worldwide. The presence of As in groundwater poses a threat as it not only affects crop productivity but also contaminates food chain. Therefore, it is essential to understand molecular mechanisms underlying uptake, transport and accumulation of As in plants. In recent past, natural variation in Arabidopsis thaliana has been utilized to understand molecular and genetic adaptation under different stresses. In this study, responses of Arabidopsis accessions were analyzed at biochemical and molecular levels towards arsenate [As(V)] stress. On the basis of reduction in root length, accessions were categorized into tolerant and sensitive ones towards As(V). Root length analysis led to the identification of Col-0 (<10% reduction) and Slavi-1 (>60% reduction) as the most tolerant and sensitive accessions, respectively. Comparative genome-wide expression analysis revealed differential expression of 168 and 548 genes in Col-0 and Slavi-1, respectively, with 120 common differentially expressed genes. A number of genes associated with defense and stress-response, transport system, regulatory mechanisms and biochemical processes showed differential expression in contrasting accessions. The study provides an insight into the molecular mechanisms associated with stress response and processes involved in adaptation strategies towards As stress., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Arsenic impairs male reproductive functions. However, it is not clear whether different arsenic compounds similarly affect fertility. In this study, we compared the impact of sodium arsenite and arsenate on sperm quality and fertility. After 56 d exposure, male Wistar rats were mated and pregnant females were evaluated by fertility indexes. Clearly, exposure to 10 mg/L arsenite reduced daily sperm production via H 2 O 2 overproduction and germ cells loss. Animals from this group also showed a decrease in epididymal sperm counts and percentage of sperm with intact membranes. Moreover, they presented low fertility potential and high preimplantation loss. In contrast, 10 mg/L arsenate caused oxidative stress in testis, mineral imbalance in epididymis, and sperm membranes damage, with no effects on fertility. Both arsenic compounds at 0.01 mg/L altered reproductive parameters. We concluded that arsenite is more harmful than arsenate to sperm quality and male fertility, with negative influences in early pregnancy., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The arsenate (As(V)) biotransformation by Microcystis aeruginosa in a medium with different concentrations of nitrogen (N) and phosphorus (P) has been studied under laboratory conditions. When 15μg/L As(V) was added, N and P in the medium showed effective regulation on arsenic (As) metabolism in M. aeruginosa, resulting in significant differences in the algal growth among different N and P treatments. Under 0.2mg/L P treatment, increases in N concentration (4-20mg/L) significantly stimulated the cell growth and therefore indirectly enhanced the production of dimethylarsinic acid (DMA), the main As metabolite, accounting for 71%-79% of the total As in the medium. Meanwhile, 10-20mg/L N treatments accelerated the ability of As metabolization by M. aeruginosa, leading to higher contents of DMA per cell. However, As(V) uptake by M. aeruginosa was significantly impeded by 0.5-1.0mg/L P treatment, resulting in smaller rates of As transformation in M. aeruginosa as well as lower contents of As metabolites in the medium. Our data demonstrated that As(V) transformation by M. aeruginosa was significantly accelerated by increasing N levels, while it was inhibited by increasing P levels. Overall, both P and N play key roles in As(V) biotransformation processes., (Copyright © 2017. Published by Elsevier B.V.)

Inorganic P i is involved in all major biochemical pathways. Here we describe a previously unreported activity of P i We show that P i and its structural mimics, vanadate and arsenate, enhance nascent transcript cleavage by RNA polymerase (RNAP). They engage an Mg 2+ ion in catalysis and activate an attacking water molecule. P i , vanadate, and arsenate stimulate the intrinsic exonuclease activity of the enzyme nearly 2,000-fold at saturating concentrations of the reactant anions and Mg 2+ This enhancement is comparable to that of specialized transcript cleavage protein factors Gre and TFIIS (3,000- to 4,000-fold). Unlike these protein factors, P i and its analogs do not stimulate endonuclease transcript cleavage. Conversely, the protein factors only marginally enhance exonucleolytic cleavage. P i thus complements cellular protein factors in assisting hydrolytic RNA cleavage by extending the repertoire of RNAP transcript degradation modes., Competing Interests: The authors declare no conflict of interest., (Copyright © 2018 the Author(s). Published by PNAS.)

The contribution of the phosphate transporters (PHTs) in uptake of arsenate (As 5+ ) and phosphate (P) is a widely recognized mechanism. Here we investigated how P regulates the uptake of As 5+ and the subsequent effects on growth and relative expression of PHTs. The study was conducted on 3 barley genotypes differing in As tolerance (ZDB160, As-tolerant; ZDB115, moderately tolerant; ZDB475, As-sensitive) using a hydroponic experiment. There were 3 As 5+ (0, 10 and 100µM) and 3P (0, 50 and 500µM) levels. The results showed that the negative effect of As stress on plant growth, photosynthesis and cell ultra-structure is As dose and barley genotype dependent, confirming the distinctly genotypic difference in As tolerance. As uptake and accumulation in plant tissues are closely associated with inhibited extent of growth and photosynthesis, with the tolerant genotype ZDB160 having lower As content than other two genotypes. The toxic effect caused by As stress could be alleviated by P addition, mainly due to reduced As uptake. Moreover, the tolerant genotype showed relatively lower expression PHTs than sensitive ones upon exposure to both As stress and P addition, suggesting regulation of PHTs expression is a major mechanism for relative uptake of As and P, in subsequence affecting As tolerance. Moreover, among 6 PHTs examined in this study, the expressions of PHT1.3, PHT1.4 and PHT1.6 showed the marked difference among the three barley genotypes in responses to As stress and P addition, indicating further research on the contribution of phosphate transporters to As and P uptake should be focused on these PHTs., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Relations between phosphate and arsenate are important but inconsistent to influence arsenic (As) phytotoxicity depending on many plant and soil factors. Present research aimed to investigate the phosphate and arsenate interactions in sunflower (Helianthus annuus L.) grown in alkaline calcareous soil for 18 weeks under natural environmental conditions at three arsenate [0 (As 0 ), 40 (As 40 ), and 80 (As 80 ) mg As kg -1 soil as sodium arsenate] and three phosphate [0 (P 0 ), 100 (P 100 ), and 200 (P 200 ) mg P 2 O 5  kg -1 soil as diammonium phosphate] levels. The plants were grown in pots according to completely randomized design with five replications. Ionic and physiological parameters were measured at 40 days after treatment completion. Arsenic contamination with As 40 and As 80 increased root and shoot As concentration with relatively higher concentration in roots, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) while decreased plant P, chlorophyll, protein, and glutathione (GSH), and consequently plant growth, yield, and yield attributes. Addition of P 100 and P 200 under As stress reduced As transfer from soil to roots to shoots, MDA concentration, SOD, CAT, and POD activities while increased GSH, leaf protein, chlorophyll, and growth characteristics as well as achene yield compared to As-treated plants without additional P. In conclusion, P-induced inhibition of As transfer from soil to roots to shoots and reduction in MDA concentration accompanied with an increase in the synthesis of protein, chlorophyll, and GSH could be the main mechanisms responsible for lowered As toxicity in sunflower, leading to mitigation of potential risks of As contamination to food chain and human health.

Arsenic contamination in drinking water is a worldwide issue, posing threat to human health. Arsenic is an endocrine system disruptor, however, limited information is available regarding its long-term effects on thyroid endocrine system at low exposure. In this study, we assessed the thyroid toxicity of arsenate (AsV) and arsenite (AsIII) at 10-100 μg L -1 in juvenile mice after 8-week of exposure via drinking water. After 1-2 week, AsV and AsIII had little influence on thyroxine (T4) level (56.3-64.7 μg L -1 ) in mouse blood compared to control mice at 57.3-60.7 μg L -1 . However, after 4-8 weeks, 10 μg L -1 AsIII or AsV increased T4 levels to 83.8-88.8 μg L -1 compared to control treatment at 77.2-80.0 μg L -1 , while 100 μg L -1 AsV or AsIII decreased T4 levels except for 100 μg L -1 AsIII for 8 weeks. Based on transmission electron microscopy, exposure to 100 μg L -1 AsIII or AsV for 8 weeks caused thyroid gland damage. In addition, exposure to AsV or AsIII at 10 or 100 μg L -1 impacted gene transcription of hypothalamic-pituitary-thyroid axis including thyroid stimulating hormone and iodothyronine deiodinases. Our data demonstrated that exposing to low levels of AsIII or AsV disrupted T4 homeostasis, influenced the related gene transcription and damaged the thyroid glands in juvenile mice., (Published by Elsevier Ltd.)

The adsorption reactions of arsenate with ferric hydroxide minerals and amorphous ferric hydroxide play an important role in affecting the transport and fate of arsenate in the environment. Previous studies have investigated formation of mono- and bidentate complexes between arsenate and ferric hydroxide. Based on AsFe coordination numbers, there is spectroscopic evidence that arsenate may also form tridentate complexes with ferric hydroxide. However, the nature of these complexes and the reaction energies and activation barriers for their formation have not been investigated. This research used density functional theory (DFT) calculations to determine the structure of possible tridentate complexes and to determine reaction energies and activation barriers for forming different structures. Tridentate binding between arsenate and ferric hydroxide was found to be thermodynamically favorable for arsenate binding to two or three adjacent dioctahedral ferric hydroxide clusters. In addition, arsenate was also observed to form AsOAs bonds simultaneously to forming bidentate binuclear bonds with ferric hydroxide. The AsFe distances in the tridentate complexes differed from those calculated for bidentate complexes by an average distance of only 0.045 Å. This suggests that spectroscopic methods (EXAFS) may not be able to distinguish bidentate from tridentate complexes based on interatomic distances. Formation of tridentate complexes required overcoming activation barriers ranging from 13 to 51 kcal/mol. Breaking of tridentate complexes had even greater activation barriers ranging from 18 to 62 kcal/mol. This suggests that tridentate complexation may contribute to previously observed extremely slow adsorption and desorption reactions of arsenate with ferric hydroxide., (Copyright © 2017 Elsevier Ltd. All rights reserved.)