Arsenic Treatment Research Articles

A new perspective on small-scale treatment systems for arsenic affected groundwater

This work provides a new perspective on small-scale treatment systems to remove arsenic from groundwater for potable applications in low-income communities. Data corroborated from the literature highlight a significant challenge to providing potable water in a financially sustainable manner in arsenic affected areas. Analysis of the literature also reveals notable deficiency in the current practice, especially the overfocus on household-scale treatment systems for arsenic affected groundwater without adequate maintenance, monitoring, and a systematic cost–benefit analysis. Accurate and reliable analysis of arsenic in water samples at relevant health guideline values is costly and technologically demanding for low-income communities. Significant discrepancy in the performance of household-scale treatment systems can be attributed to the lack of maintenance and systematic monitoring. Moreover, data on the maintenance and compliance monitoring cost of small-scale arsenic treatment systems are very limited in the literature, and the available data show an exponential increase in maintenance cost per treatment capacity unit as the treatment size decreases. On the other hand, significant opportunities exist to increase performance reliability and reduce water treatment cost by taking advantage of the current digital transformation of the water sector. The analysis in this work suggests the need to reframe current practice towards commune-scale treatment systems as an interim step before centralised water supply is available. • Arsenic contaminated groundwater significantly impacts low-income communities. • Co-contaminants must also be removed to meet drinking water standard. • Inadequate maintenance and monitoring of household-scale systems exists. • Beyond the minimum scale, performance is unreliable or unassessable. • Digitally enabled systems play an interim step before centralised water supply.

Silicon Modulates Molecular and Physiological Activities in Lsi1 Transgenic and Wild Lemont Rice Seedlings under Arsenic Stress

Arsenic is one of the most dangerous metalloids, and silicon is a helpful element supporting plants to withstand stress. In this study, three factors were considered, including rice accessions with three different lines, including Lsi1-RNAi line (LE-R), Lsi1 overexpression line (LE-OE), and their wild type (LE-WT), and silicon and arsenic treatments with two different levels. Analysis of variance in dry weight biomass, protein content, arsenic, and silicon concentration has shown a significant interaction between three factors. Further analysis showed that the silicon concentration of all rice seedlings under silicon treatments increased significantly. The LE-OE line has shown a higher ability to absorb silicon in hydroponic conditions than the wild type, and when the seedlings were exposed to arsenic, the concentration of arsenic in all lines increased significantly. Adding silicon to over-expressed rice lines with the Lsi1 gene creates better arsenic resistance than their wild type. These findings confirmed antagonism between silicon and arsenic, and seedlings exposed to arsenic showed a reduction in silicon concentration in all rice lines. RNA-seq analysis showed 106 differentially expressed genes in the LE-OE line, including 75 up-regulated genes and 31 down-regulated genes. DEGs in the LE-R line were 449 genes, including 190 up-regulated and 259 down-regulated genes. Adding treatment has changed the expression of Calcium-binding EGF domain-containing, Os10g0530500, Os05g0240200 in both LE-OE and LE-R roots. They showed that transgenic cultivars were more resistant to arsenic than wild-type, especially when silicon was added to the culture medium.

Structure-tunable trivalent Fe-Al-based bimetallic organic frameworks for arsenic removal from contaminated water

Arsenic pollution of groundwater and surface water has come to the attention of the public. To explore economically affordable and efficient adsorbents for the treatment of arsenic, bimetallic MOFs based on trivalent iron and aluminum were synthesized and used to capture arsenic from wastewater. Characterization methods including SEM, EDX, XRD, and N2 adsorption–desorption were applied to analyze the morphology and element content, crystal structure, porosity and specific surface area of the Fe/Al-BDC-NH2 materials. The microstructures of bimetallic MOFs were tuned through changing the ratio of Al and Fe in the precursor material. Adsorption results show that introducing aluminum into the iron-based material formed bimetallic Fe/Al-BDC-NH2 MOFs that had much better adsorption performance for arsenic than the monometallic Fe-BDC-NH2 or Al-BDC-NH2 MOF. The adsorption isotherm of bimetallic MOF materials for arsenic is in accordance with the Langmuir isotherm model, and the maximum adsorption capability of Fe/Al-BDC-NH2 (1:1) at 298 K was 146.8 mg g−1. The kinetics of arsenic adsorption follow the pseudo-second-order model. Also, the thermodynamics indicate that arsenic adsorption is endothermic. Fe/Al-BDC-NH2 (1:1) is suitable for removal of arsenic from wastewater in a relatively wide pH range (5.0–9.0). Within this pH range, Fe and Al are hardly dissolved in water after arsenic capture, and this indicates that Fe/Al-BDC-NH2 (1:1) is very stable and suitable for arsenic capture from water without generating secondary pollution. Furthermore, through FTIR and XPS analysis, ligand exchange was identified as the main adsorption mechanism of Fe/Al-BDC-NH2 (1:1) for arsenic.

An Accessible Alternative to Melarsomine: "Moxi-Doxy" for Treatment of Adult Heartworm Infection in Dogs.

Canine heartworm infection, caused by the filarial parasite Dirofilaria immitis, represents a serious and expanding animal welfare concern that is expected to increase due to the effects of climate change and the COVID-19 pandemic. A body of evidence has emerged to support the use of a non-arsenical adulticide treatment protocol, using moxidectin and doxycycline to kill adult heartworms over a prolonged period. While a three-dose protocol using the arsenical drug melarsomine is currently the safest and most effective treatment for heartworm infection, this drug is not available in some countries and is inaccessible for many owners and animal shelters. Moxidectin-doxycycline (moxi-doxy) provides a viable alternative to no treatment at all, in cases where arsenical treatment is not possible. Based on current evidence, the most effective non-arsenical treatment regimen is doxycycline 10 mg/kg PO q 12 or 24 h for 28 days, combined with topical moxidectin at label dose. Moxidectin is repeated monthly until no antigen detected (NAD) status is confirmed. Sustained release injectable moxidectin, in combination with doxycycline, may provide an alternative in remote regions or in settings where significant compliance or accessibility concerns exist, but more studies are needed. In moxi-doxy protocols, doxycycline should be repeated annually until NAD. This review summarizes the safety and efficacy of moxi-doxy, addresses controversies surrounding this treatment approach, and provides detailed recommendations for treatment regimens and post-treatment testing.

Persistence and reversibility of arsenic-induced gut microbiome and metabolome shifts in male rats after 30-days recovery duration.

The metabolites of gut microbiome are important host-health regulating factors and can be interrupted when the host is exposed to environmental pollutant via ingestion route. Arsenic contaminated drinking water is one of the most serious environmental health problems worldwide. Therefore, the arsenic-induced alterations of gut microbiome and metabolome, especially the persistence and reversibility of the alterations after the long-term arsenic exposure will be interesting to know. In this study, we investigated the relationship between gut microbiota and metabolites in male rats both after the 30-days arsenic treatment and 30-days recovery duration. The composition and diversity of gut microbiota were affected significantly by the treatment, but they presented partial improvement in recovery duration. Moreover, arsenic exposure induced the significant changes of 73 metabolites, which involved in the metabolism of glycerophospholipid, linoleic acid, as well as the biosynthesis of phenylalanine, tyrosine and tryptophan. Although it had a persistent effect, the restoration of glycerophospholipid metabolism was observed in the 30-days recovery. Integration analysis further correlated the arsenic impacting microbes with some important differential metabolites. Lactobacillus associated with the decreases of phosphatidylethanolamine(34:1), 16alpha-hydroxydehydroepiandrosterone 3-sulfate, seryltryptophan and alanyltyrosine in recovery duration. Lactobacillus strains have potential to work as protective agents against arsenic toxicity by restoring perturbed glycerophospholipid metabolism. In summary, arsenic significantly disrupted gut microbiome and metabolome, but the disruptions are reversible to some extent after a 30-days recovery.

Combining geophysics and material science for environmental remediation: Real-time monitoring of Fe-biochar arsenic wastewater treatment

In a column set-up, Fe modified biochar produced from date palm leaves was used to remove As (1 mg L−1) from a laboratory-prepared wastewater. The wastewater treatment process was monitored in real-time by spectral induced polarization (SIP), over a wide range of frequencies (0.01–1000 Hz). Both 5 and 10% biochar-amended columns achieved As removal exceeding 98%. The SIP parameters appear to be sensitive on As removal processes, with the recorded trend following the conventional geochemical monitoring, while offering higher temporal resolution.

Arsenic disrupts neuronal insulin signaling through increasing free PI3K-p85 and decreasing PI3K activity

Previously, we reported that prolonged arsenic exposure impaired neuronal insulin signaling. Here we have further identified novel molecular mechanisms underlying neuronal insulin signaling impairment by arsenic. Arsenic treatment altered insulin dose-response curve and reduced maximum insulin response in differentiated human neuroblastoma SH-SY5Y cells, suggesting that arsenic hindered neuronal insulin signaling in a non-competitive like manner. Mechanistically, arsenic suppressed insulin receptor (IR) kinase activity, as witnessed by a decreased insulin-activated autophosphorylation of IR at Y1150/1151. Arsenic decreased the level of insulin receptor substrate 1 (IRS1) but increased the protein ratio between PI3K regulatory subunit, p85, and PI3K catalytic subunit, p110. Interestingly, co-immunoprecipitation demonstrated that arsenic did not alter a level of PI3K-p110/PI3K-p85 complex while increased PI3K-p85 levels in a PI3K-p110 depletion supernatant resulted from PI3K-p110 immunoprecipitation. These results indicated that arsenic increased PI3K-p85 which was free from PI3K-p110 binding. In addition, arsenic significantly increased interaction between IRS1 and PI3K-p85 but not PI3K-p110, suggesting that there may be a fraction of free PI3K-p85 interacting with IRS1. In vitro PI3K activity demonstrated that arsenic lowered PI3K activity in both basal and insulin-stimulated conditions. These results suggested that the increase in free PI3K-p85 by arsenic might compete with PI3K heterodimer for the same IRS1 binding site, in turn blocking the activation of its catalytic subunit, PI3K-p110. Taken together, our results provide additional insights into mechanisms underlying the impairment of neuronal insulin signaling by arsenic through the reduction of IR autophosphorylation, the increase in free PI3K-p85, and the impeding of PI3K activity.

Removing co-occurring contaminants of arsenic and vanadium with full-scale arsenic adsorptive media systems.

The U.S. Environmental Protection Agency conducted an Arsenic Demonstration Program (ADP) whereby 50 full, small-scale arsenic removal treatment systems were evaluated for removing arsenic to below the maximum contaminant level of 10 μg/L and their operating cost for a minimum of 1 year. The majority (28) of the systems installed were adsorptive media (AM) technology with the media replaced when exhausted. This paper reports on the results of two ADP projects and two laboratory rapid small-scale column tests (RSSCTs) using the iron-based media, Bayoxide E33 (E33) AM for the removal of arsenic (As) and the co-occurring contaminants (COCs) of vanadium and to a lesser degree fluoride (F) and nitrate (NO3). The ADP studies found that the AM effectively removed the COC of V, but with a lower removal capacity than of As. One ADP study found the AM to be ineffective for the removal of F and NO3. The RSSCT conducted on two other source waters also found vanadium to be removed by the same AM. The study results suggested the AM selectively sequence of As > V > F = N. The study also investigated the AM to achieve an As limit of 5 μg/L. The AM was found to reduce As to below 5 μg/L with around 30% shorter treatment run lengths.

Estudio comparativo de un proceso químico y un proceso biotecnológico para la remoción de bismuto de concentrados mineros

In 2018, approximately 17.7 billion metric tons of minerals were produced worldwide, which represent a great importance in the industrial sector. However, most of the minerals are bound with metallic elements, which lower the price of the metals of interest. Secondary materials in valuable metal extraction processes can cause various problems in the mining industry, both economic and environmental. This research aimed evaluate two treatments for the reduction of the bismuth concentration in gold and silver mineral concentrates: Bioleaching and co- precipitation with trioxide arsenic treatment, in the first, native microorganisms of the mineral to be treated were used to reduce the concentration of bismuth; in the second, arsenic trioxide was added in order to form a precipitate that contained bismuth.. The results showed that the chemical co-precipitation treatment with arsenic trioxide can decrease the Bi concentration to a greater extent compared to the bioleaching treatment, up to 16% of the initial concentration, in addition to reducing the concentration of other undesirable elements in metals such as antimony and cadmium by 32 and 11% respectively. From this research work, a collaboration of two techniques can be proposed for a higher reduction of concentration and with greater efficiency.

The SLIM1 transcription factor is required for arsenic resistance in Arabidopsis thaliana.

The transcriptional regulators of arsenic-induced gene expression remain largely unknown. Sulfur assimilation is tightly linked with arsenic detoxification. Here, we report that mutant alleles in the SLIM1 transcription factor are substantially more sensitive to arsenic than cadmium. Arsenic treatment caused high levels of oxidative stress in the slim1 mutants, and slim1 alleles were impaired in both thiol accumulation and sulfate accumulation. We further found enhanced arsenic accumulation in roots of slim1 mutants. Transcriptome analyses indicate an important role for SLIM1 in arsenic-induced tolerance mechanisms. The present study identifies the SLIM1 transcription factor as an essential component in arsenic tolerance and arsenic-induced gene expression. Our results suggest that the severe arsenic sensitivity of the slim1 mutants is caused by altered redox status.

Arsenicals, the Integrated Stress Response, and Epstein-Barr Virus Lytic Gene Expression.

Following our observation that clofoctol led to Epstein–Barr virus (EBV) lytic gene expression upon activation of the integrated stress response (ISR), we decided to investigate the impact of As2O3 on viral lytic gene expression. As2O3 has also been reported to activate the ISR pathway by its activation of the heme-regulated inhibitor (HRI). Our investigations show that As2O3 treatment leads to eIF2α phosphorylation, upregulation of ATF4 and TRB3 expression, and an increase of EBV Zta gene expression in lymphoid tumor cell lines as well as in naturally infected epithelial cancer cell lines. However, late lytic gene expression and virion production were blocked after arsenic treatment. In comparison, a small molecule HRI activator also led to increased Zta expression but did not block late lytic gene expression, suggesting that As2O3 effects on EBV gene expression are also mediated through other pathways.

Electrochemically modified adsorbents for treatment of aqueous arsenic: Pore diffusion in modified biomass vs. biochar

Canola straw-based biomass and biochar adsorbents were electrochemically modified and used to remove arsenate (As(V)) from water. Studying the effects of the modification parameters on the As(V) adsorption capacity of the modified materials showed that the materials treated at lower pH (3) and drying temperatures (60 °C) had higher As(V) uptake. The modification conditions were optimized to obtain optimum modified biomass (OBM) and biochar (OBC) with the highest As(V) adsorption capacity. Characterization of the OBM and OBC indicated that the deposited iron oxide on the surface of the adsorbents was goethite. The adsorption isotherms and kinetic data suggested that a hybrid adsorption mechanism took place under the experimental conditions with a higher probability of heterogeneous multilayer chemisorption. Solid-phase speciation of the sorbed As(V) indicated a negligible reduction (2.5%) of As(V) to arsenite (As(III)) on OBM, while no reduction occurred on OBC. The liquid film mass transfer coefficient (kf) and effective pore diffusion coefficient (Dp) were estimated using a shrinking core model combined with a genetic algorithm. A higher tortuosity factor of 3.75 for the OBM was obtained as compared to 2.93 for the OBC. Overall, the applied electrochemical modification successfully enhanced the As(V) sorption capacity of both the biomass and biochar from 8 to 766 and 25 to 922 µg/g, respectively, indicating promising potential of this method for preparation of high performance adsorbents.

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.

Nature of sorption of trivalent arsenic on novel iron oxyhydroxide stabilized starch/OMMT composite: A mechanistic approach.

Materials which are chemically, energetically and operationally acceptable for arsenic water treatment are highly required. In this study a hybrid material (SICC) of aminated starch, oxyhydroxide of iron and OMMT clay has been demonstrated for arsenic treatment. This new material was highly efficient in arsenic water treatment which could reduce arsenic concentration far below detection limits. All binding interactions during material preparation and arsenic sorption were exclusively characterized with FT-IR, XRD and other spectroscopic tools. A molecular modeling on the basis of density functional theory was carried out to verify the above findings. Influence of material dose, treatment time, initial ion concentration, varying temperatures, etc., on extent of sorption was studied in detail. The thermodynamic parameters viz. ΔG (>-11 kJ/mol), ΔH (42.48 kJ/mol), ΔS (177.6 JK-1 mol-1) and E a (59.16 kJ/mol) determined the feasibility of the process, its endothermic behavior and most importantly the chemical nature of the sorption accompanied by ion-exchange to some extent. The sorption followed a monolayer chemisorption pattern as determined by the Langmuir model (R2 = 0.973, R L = 0.081) with a qmax = 2.04 at 303 K. The binding of As(III) on the material was governed by a pseudo second order kinetic model.

Alkali circulating leaching of arsenic from copper smelter dust based on arsenic-alkali efficient separation

Leaching arsenic from solid waste selectively and removing arsenic from alkaline leachate efficiently are two key points in alkali treatment of copper smelter dust, and the latter is challenging. In this study, composite salt precipitation of magnesium ammonium arsenate (NH4MgAsO4·6H2O), similar to magnesium ammonium phosphate (NH4MgPO4·6H2O), was proposed to solve the difficult problem of separation arsenic from alkali. Based on the thermodynamic analysis, the selective leaching of arsenic from copper smelting dust was carried out in the NaOH-Na2S system. In the alkali leaching system, more than 80% arsenic can be leached out from the dust with the diffusion-controlled type in the Avrami model, while the leaching rates of valuable metals are less than 0.5%. For the strong alkaline leachate containing arsenic obtained by alkali leaching, the selective removal of arsenic was achieved by adding magnesium salt and ammonium salt. With the change of the amount of magnesium salt and ammonium salt, the sedimentation performance and composition of the arsenic slag changed accordingly. At the mole ratio of NH4+: As = 8:1 and Mg2+: As = 1.5:1, 96.38% of arsenic was removed, and the content of arsenic in the arsenic slag composed of MgNH4AsO4·6H2O reached 28.96%. On this basis, the circulating alkali leaching of copper smelter dust based on arsenic-alkali separation was successfully carried out. The whole scheme is not only economical and safe, but also achieves the reuse of wastewater without secondary pollution, which provides an alternative solution for the treatment of arsenic containing solid waste.

Formation and in-situ dissociation of particulate arsenic in the zinc-containing flue gas from nonferrous metallurgy

Pyrometallurgy to collect crystalline arsenic trioxide is one of the most promising strategies to cut off the environmental risk of arsenic, while it is still difficult to realize the in-situ release and effective collection of arsenic trioxide in nonferrous metallurgy flue gas. Here the formation process of particulate arsenic was clarified, and the inlet sulfur dioxide and oxygen presented important effects on arsenic concentration and toxicity of the formed particulate arsenic. Moreover, we first proposed using pyrite as vulcanizing additive to promote the in-situ dissociation of particulate arsenic. The dissociation of particulate arsenic consisted of two-stepwise stages. First, zinc arsenate was transformed into zinc arsenite and zinc sulfide without the release of arsenic. Next, zinc arsenite was decomposed to zinc sulfide and arsenic trioxide, realizing the in-situ dissociation. Compared with the traditional vulcanization technology, pyrite was further exploited for its complete oxidation to provide all the sulfur. This study provides a facile and sustainable way for cleaning treatment of particulate arsenic in nonferrous metallurgy flue gas.

Effects of the Cooling Rate on the Solidified Structure and Toxic Leaching of an Arsenic Matte

The conversion of arsenic-containing waste residues into arsenic matte can be an important direction for arsenic treatment. In this paper, different parts of factory samples were first taken for study, and it was found that the leaching amount of arsenic at the chilling layer is noticeably low. Then, the effects of the cooling rate on the phase, microstructure, and chemical compositions and the subsequent toxicity leaching of the arsenic matte were studied. The results show that the alloy structure was obviously refined and the cavity size was also significantly reduced with an increase in cooling rate. Many large-strip FeS and arsenic-containing iron solid solutions were embedded in the matrix (Fe2As) of the furnace-cooled and air-cooled samples; additionally, the Fe–As–S phase was probably caused by an insufficient phase separation of FeS from Fe2As in the rapid cooling process of die cooling and water cooling. FeS in the factory samples was dissolved in the leaching solution, while Fe2As could resist the corrosion of the leaching solution; therefore, it was speculated that the dissolution of arsenic was caused by the dissolution of FeS. The leaching mechanism was also discussed in this paper. The cooling rate affects phase, microstructure, and chemical compositions and toxicity leaching of the arsenic matte, which speculated that the dissolution of arsenic was caused by the dissolution of FeS

Drinking Water Supply Options in Arsenic and Salinity Affected Areas of Bangladesh: A Case Study

Widespread groundwater arsenic contamination in south, south-western and north-eastern regions and high salinity in the south-western coastal region are the two major challenges for drinking water supply in Bangladesh. In this study, we assessed various water supply technologies used for mitigating arsenic and salinity in Laksam of Cumilla and Assasuni of Satkhira district. Water samples were analyzed for Arsenic, Iron, Chloride (indicator for salinity) and FC from different water extraction systems (shallow, deep and Tara tubewells), groundwater arsenic treatment units (SIDKO and READ-F), rainwater harvesting systems (RWH), pond sand filters (PSF), and managed aquifer recharge units. Most shallow tubewells, both in Laksam and Assasuni, have been found to produce arsenic contaminated water. But water from deep and Tara tubewells have been found arsenic-free, though high concentration of iron was observed in the wells in Laksam. Rainwater harvesting systems, PSF and MAR units in Assasuni have been found to provide water free from the common chemical contaminants but suffer from high bacterial contamination. Deep tubewell appear to be the most preferred option where a suitable aquifer is available. The community-scale groundwater treatment systems would require strong operation and maintenance support from the service providers to be successful.&#x0D; Environ. Sci. &amp; Natural Resources, 12(1&amp;2): 215-223, 2019

Differential effects of arsenic species on Nrf2 and Bach1 nuclear localization in cultured hepatocytes

Arsenic is a ubiquitous metalloid element present in both inorganic and organic forms in the environment. The liver is considered to be a primary organ of arsenic biotransformation and methylation, as well as the main target of arsenic toxicity. Studies have confirmed that Chang human hepatocytes have an efficient arsenic methylating capacity. Our previous studies have proven that arsenite activates nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in hepatocytes. This study aimed to explore the activation of the Nrf2 pathway upon treatment of arsenic in various forms, including inorganic and organic arsenic. Our results showed that inorganic arsenic—both As2O3 and Na2HAsO4 significantly induced the expression of Nrf2 protein and mRNA, enhanced the transcription activity of Nrf2, and induced the expression of downstream target genes. These results confirmed the inorganic arsenic-induced Nrf2 pathway activation in hepatocytes. Although all arsenic chemicals used in the study induced Nrf2 protein accumulation, the organic arsenic C2H7AsO2 did not affect the expression of Nrf2 downstream genes which were elevated by inorganic arsenic exposures. Through qRT-PCR and Nrf2 luciferase reporter assays, we further confirmed that C2H7AsO2 neither increased Nrf2 mRNA level nor activated the Nrf2 transcription activity. Mechanistically, our results confirmed inorganic arsenic-induced both the nuclear import of Nrf2 and export of Bach1 (BTB and CNC homology 1), which is an Nrf2 transcriptional repressor, while organic arsenic only induced Nrf2 translocation. The unique pattern of Nrf2 regulation by organic arsenic underlines the critical role of Nrf2 and Bach1 in the arsenic toxicology.

Research Progress on the treatment of arsenic pollution by manganese oxide

Arsenic is a kind of protoplasmic poison, which exists widely in the natural environment. Consuming too much arsenic can cause a number of health problems. Manganese oxide plays an important role in arsenic pollution removal technology. In this paper, arsenic hazard and its treatment methods and the application of manganese oxides in arsenic pollution treatment are summarized, and the prospect of research on arsenic pollution treatment by manganese oxides is put forward.