Organic Arsenic Research Articles

Arsenic in medicine: past, present and future.

Arsenicals are one of the oldest treatments for a variety of human disorders. Although infamous for its toxicity, arsenic is paradoxically a therapeutic agent that has been used since ancient times for the treatment of multiple diseases. The use of most arsenic-based drugs was abandoned with the discovery of antibiotics in the 1940s, but a few remained in use such as those for the treatment of trypanosomiasis. In the 1970s, arsenic trioxide, the active ingredient in a traditional Chinese medicine, was shown to produce dramatic remission of acute promyelocytic leukemia similar to the effect of all-trans retinoic acid. Since then, there has been a renewed interest in the clinical use of arsenicals. Here the ancient and modern medicinal uses of inorganic and organic arsenicals are reviewed. Included are antimicrobial, antiviral, antiparasitic and anticancer applications. In the face of increasing antibiotic resistance and the emergence of deadly pathogens such as the severe acute respiratory syndrome coronavirus 2, we propose revisiting arsenicals with proven efficacy to combat emerging pathogens. Current advances in science and technology can be employed to design newer arsenical drugs with high therapeutic index. These novel arsenicals can be used in combination with existing drugs or serve as valuable alternatives in the fight against cancer and emerging pathogens. The discovery of the pentavalent arsenic-containing antibiotic arsinothricin, which is effective against multidrug-resistant pathogens, illustrates the future potential of this new class of organoarsenical antibiotics.

Comparative Study of Roxarsone Reduction by Shewanella oneidensis MR-1 and Cellulomonas sp. Strain Cellu-2a

Roxarsone, an organoarsenic compound, has been used extensively as an additive in poultry feed to promote animal growth. Although roxarsone is moderately toxic, it can be converted into more toxic compounds upon exposure to the environment, resulting in human health risks. This article reports on a comparative study of roxarsone reduction by fermentative, anaerobic Cellulomonas sp. Cellu-2a and a widely distributed metal-reducing bacterium, Shewanella oneidensis MR-1. The strain Cellu-2a showed a faster roxarsone reduction capability by fermentative growth than by MR-1 in anaerobic respiration. With an environmentally relevant mineral, hydrous ferric oxide (HFO) included in the incubations, there was a rather rapid abiotic (indirect, heterogeneous) reduction of roxarsone by the solid phase Fe(II) in HFO generated by reduction of Fe(III) of HFO by MR-1, while still direct reduction was major reaction by Cellu-2a even with HFO. This study provides evidence of direct and/or indirect bacterial reduction of roxarsone in fermentative conditions as well as in anaerobic respiration conditions, at exposure to the environment, which would assist understanding of environmental behaviors of roxarsone in biological settings with HFO, a naturally occurring ubiquitous mineral class.

Adsorptive remediation of organic pollutant and arsenic (V) ions from water using Fe3O4-MnO2 nanocomposite

The presence of various pollutants in water poses a threat to human health. In this study, we focused on the removal of organic pollutant methylene blue (MB) and As(V) from the water by using Fe3O4-MnO 2 nanocomposite. The surface area of the as-prepared nanocomposite was found to be 237.39 m2/g. The nanocomposite was further characterized by using analytical techniques like powder XRD, SEM, VSM and transmission electron microscope. The results of the transmission electron microscope (TEM) showed Fe3O4 cores coated by a MnO 2 shell. VSM analysis showed that the Fe3O4-MnO 2 nanocomposite has ferromagnetic behavior. The efficiency of Fe3O4-MnO 2 nanocomposite for the removal of methylene blue (MB) and As(V) from the water was studied by varying the pollutant concentration and contact time. The results showed a maximum adsorption capacity of 146.1 mg/g for MB and 16.6 mg/g for As(V). The sorption equilibrium data fitted to Langmuir adsorption model for both MB and As(V) adsorption. The nanocomposite was magnetically separable and tested for five consecutive adsorption–desorption cycles. The Fe3O4-MnO 2 nanocomposite retained 70% of its adsorption capacity over five consecutive cycles of regeneration for MB as well as As(V). The result obtained suggest that Fe3O4-MnO 2 nanocomposite can be a promising adsorbent for the removal of methylene blue and As(V) present in water.

Recent progress on arsenic-containing functional polymers

Heteroatom-fused polymer materials can realize structures, functions, and reactivities that cannot be achieved with polymers that lack fused heteroatoms in their structure. Although numerous elements have been used that impart unique properties to polymer materials, arsenic has typically been avoided because of the lack of safe and facile synthetic methods for organoarsenic compounds. Recently, practical As–C bond formation reactions have been developed, resulting in advances in functional organoarsenic chemistry. In this minireview, arsenic-containing polymer materials were discussed.

Organoarsenic compounds in water samples – the problem of hydride generation atomic absorption spectroscopic method

Organoarsenic compounds in water samples – the problem of hydride generation atomic absorption spectroscopic method

Global genomic analysis of microbial biotransformation of arsenic highlights the importance of arsenic methylation in environmental and human microbiomes

Arsenic is a ubiquitous toxic element, the global cycle of which is highly affected by microbial redox reactions and assimilation into organoarsenic compounds through sequential methylation reactions. While microbial biotransformation of arsenic has been studied for decades, the past years have seen the discovery of multiple new genes related to arsenic metabolism. Still, most studies focus on a small set of key genes or a small set of cultured microorganisms. Here, we leveraged the recently greatly expanded availability of microbial genomes of diverse organisms from lineages lacking cultivated representatives, including those reconstructed from metagenomes, to investigate genetic repertoires of taxonomic and environmental controls on arsenic metabolic capacities. Based on the collection of arsenic-related genes, we identified thirteen distinct metabolic guilds, four of which combine the aio and ars operons. We found that the best studied phyla have very different combinations of capacities than less well-studied phyla, including phyla lacking isolated representatives. We identified a distinct arsenic gene signature in the microbiomes of humans exposed or likely exposed to drinking water contaminated by arsenic and that arsenic methylation is important in soil and in human microbiomes. Thus, the microbiomes of humans exposed to arsenic have the potential to exacerbate arsenic toxicity. Finally, we show that machine learning can predict bacterial arsenic metabolism capacities based on their taxonomy and the environment from which they were sampled.

Assessment of the effects of organic vs. inorganic arsenic and mercury in Caenorhabditis elegans

Exposures to mercury and arsenic are known to pose significant threats to human health. Effects specific to organic vs. inorganic forms of these toxic elements are less understood however, especially for organic dimethylarsinic acid (DMA), which has recently been detected in pups of rodent dams orally exposed to inorganic sodium (meta)arsenite (NaAsO2). Caenorhabditis elegans is a small animal alternative toxicity model. To fill data gaps on the effects of DMA relative to NaAsO2, C. elegans were exposed to these two compounds alongside more thoroughly researched inorganic mercury chloride (HgCl2) and organic methylmercury chloride (meHgCl). For timing of developmental milestone acquisition in C. elegans, meHgCl was 2 to 4-fold more toxic than HgCl2, and NaAsO2 was 20-fold more toxic than DMA, ranking the four compounds meHgCl > HgCl2 > NaAsO2 ≫ DMA for developmental toxicity. Methylmercury induced significant decreases in population locomotor activity levels in developing C. elegans. DMA was also associated with developmental hypoactivity, but at >100-fold higher concentrations than meHgCl. Transcriptional alterations in native genes were observed in wild type C. elegans adults exposed to concentrations equitoxic for developmental delay in juveniles. Both forms of arsenic induced genes involved in immune defense and oxidative stress response, while the two mercury species induced proportionally more genes involved in transcriptional regulation. A transgenic bioreporter for activation of conserved proteosome specific unfolded protein response was strongly activated by NaAsO2, but not DMA at tested concentrations. HgCl2 and meHgCl had opposite effects on a bioreporter for unfolded protein response in the endoplasmic reticulum. Presented experiments indicating low toxicity for DMA in C. elegans are consistent with human epidemiologic data correlating higher arsenic methylation capacity with resistance to arsenic toxicity. This work contributes to the understanding of the accuracy and fit-for-use categories for C. elegans toxicity screening and its usefulness to prioritize compounds of concern for further testing.

Mitochondrial Toxicity of Organic Arsenicals.

Arsenic is either notorious toxicant or miracle cure for acute promyelocytic leukemia and several other diseases. It interacts with mitochondria directly or indirectly, by interacting with mitochondrial enzymes, such as respiratory chain complexes and tricarboxylic acid cycle proteins, or affecting mitochondrial homeostasis via ROS or mitochondrial outer membrane permeabilization. Given the ubiquitous presence of mitochondria and indispensable role in cellular metabolism, arsenical-mitochondrial interactions may manifest clinical importance by revealing mechanism of disease curation, preventing severe side effects, and foreseeing potential health issues. Here, we described the interaction between isolated mitochondria and arsenicals.

4种蚯蚓肠道微生物对砷毒性的响应差异研究

蚯蚓肠道是微生物多样性的一个潜在存储库。砷对蚯蚓肠道微生物群落的影响已被证实，但砷在不同蚯蚓肠道菌群中生物转化的差异仍不清楚。为了进一步阐述土壤中广泛存在的低浓度砷（浓度为5，15，25 mg/kg）对不同种类蚯蚓肠道微生物影响的差异，将4种典型蚯蚓暴露于砷污染土壤后，测定其肠道微生物组成变化，并分析砷对不同蚯蚓肠道内砷富集、形态和砷生物转化基因的影响。结果显示，所有蚯蚓组织内均存在明显的砷富集，其富集系数由高到低依次为：安德爱胜蚓（1.93） > 加州腔蚓（0.80） > 通俗腔蚓（0.78） > 湖北远盲蚓（0.52），蚯蚓组织和肠道内砷形态主要以无机砷为主，其中As （III）含量比例> 80%，部分蚯蚓组织内还发现少量有机砷。4种蚯蚓肠道微生物群落在门水平上主要以变形菌、厚壁菌和放线菌为主，并与周围土壤细菌群落组成存在显著差异。同时，在土壤和肠道内共检测到17个砷转化基因，其中蚯蚓肠道内As （V）还原和砷转运相关基因相对丰度较高，而砷（去）甲基化基因丰度较低。此外，低浓度砷污染对蚯蚓生长无显著影响，却能引起蚯蚓肠道微生物群落的紊乱。蚯蚓种类和砷污染是引起蚯蚓肠道微生物群落组成变化的主要因素。综上，蚯蚓肠道是一个微生物介导的砷生物转化的重要热区，本研究拓展了我们对土壤动物肠道内砷生物地球化学行为的认知。;Earthworm guts are thought as a potential reservoir of microbial diversity. Low concentrations of arsenic are widespread in soil and the effect of arsenic contaminant on earthworm gut microbiota has been confirmed. However, shifts of arsenic biotransformation in different earthworm gut are largely unknown. In this study, four species of earthworms were exposed to arsenic-contaminated soils to explore the difference and universality of the effects of low concentrations of arsenic (i.e., concentrations of 5, 15, and 25 mg/kg) on the gut microbiota characteristics using Illumina high-throughput sequencing, and to examine the relationships between arsenic enrichments, arsenic species and arsenic biotransformation genes in different earthworm gut. Our results demonstrated that significant arsenic bioaccumulations in all earthworm body tissues were observed. Eisenia Andrei had the highest arsenic bioaccumulation, in which the bioconcentration factor of arsenic was 1.93, followed by Metaphire californica (0.80), Metaphire vulgaris (0.78), and Amynthas hupeiensis (0.52). Inorganic arsenic (As (V) and As (III)) was predominant in earthworm body tissues and guts, where the percentage of As (III) was more than 80%. A few of organic arsenic was also observed in E. Andrei and A. hupeiensis body tissues. Gut microbial communities in four species of earthworms were dominated by Proteobacteria (22.7%), Firmicutes (25.9%), and Actinobacteria (28.0%) at the phylum level, and were significantly different from those in the surrounding soil. In addition, a total of 17 ABGs were quantified in soil and earthworm gut samples by high throughput quantitative polymerase chain reaction (HT-qPCR), a higher relative abundance of genes involved in As (V) reduction and arsenic transport, and a lower abundance of genes involved in arsenic methylation and demethylation were observed in all earthworm gut samples. The earthworm gut can be a reservoir of microbes with the capability of reducing As (V) and extruding As (III), but with little methylation and demethylation of arsenic, suggesting that ABGs played important roles in the biotransformation and bioaccumulation of arsenic. Moreover, low concentrations of arsenic did not significantly alter the survival and growth of earthworms, but it could disturb the bacterial community of earthworm gut. Changes of microbial community in the earthworm gut were mainly influenced by earthworm species and arsenic contamination. In short, this study suggested that earthworm gut was an important hotspot for the microbe-mediated arsenic biotransformation, and the findings of this study could broaden our understanding of the biogeochemical behavior of arsenic in the gut of soil animals.

Diphenylarsinic acid induced activation of MAP kinases, transcription factors, and oxidative stress-responsive factors and hypersecretion of cytokines in cultured normal human cerebellar astrocytes

Diphenylarsinic acid (DPAA) is a non-natural pentavalent organic arsenic and was detected in well water in Kamisu, Ibaraki, Japan in 2003. Individuals that had consumed this arsenic-contaminated water developed cerebellar symptoms such as myoclonus. We previously revealed that DPAA exposure in rats in vitro and in vivo specifically affected astrocytes rather than neurons among cerebellar cells. Here, we evaluated adverse effects of DPAA in cultured normal human cerebellar astrocytes (NHA), which were compared with those in normal rat cerebellar astrocytes (NRA) exposed to DPAA at 10 μM for 96 h, focusing on aberrant activation of astrocytes; increase in cell viability, activation of MAP kinases (ERK1/2, p38MAPK, and SAPK/JNK) and transcription factors (CREB, c-Jun, and c-Fos), upregulation of oxidative stress-responsive factors (Nrf2, HO-1, and Hsp70), and also hypersecretion of brain cytokines (MCP-1, adrenomedullin, FGF-2, CXCL1, and IL-6) as reported in NRA. While DPAA exposure at 10 μM for 96 h had little effect on NHA, a higher concentration (50 μM for 96 h) and longer exposure (10 μM for 288 h) induced similar aberrant activation. Moreover, exposure to DPAA at 50 μM for 96 h or 10 μM for 288 h in NHA induced hypersecretion of cytokines induced in DPAA-exposed NRA (MCP-1, adrenomedullin, FGF-2, CXCL1, and IL-6), and IL-8 besides into culture medium. These results suggested that aberrantly activated human astrocytes by DPAA exposure might play a pivotal role in the pathogenesis of cerebellar symptoms, affecting adjacent neurons, microglia, brain blood vessels, or astrocyte itself through these brain cytokines in human.

Validation of an analytical method for the determination of inorganic, organic, and total arsenic in fish sauce based on hydride generation atomic absorption spectrometry

An atomic absorption spectrometric (AAS) method was performed to determine the total, inorganic, and organic arsenic in fish sauce. The total organic arsenic was calculated from the total and inorganic arsenic values quantified using the hydride generation AAS (HG-AAS). Under optimal experimental conditions at the absorbance wavelength of 193.7 nm, the concentration of inorganic arsenic in fish sauce ranged from 0.05 to 1.2 mg/L, with a limit of detection (LOD) of 0.015 mg/L. The detectable total arsenic concentrations varied widely, ranging from 0.03 to 2.5 mg/L with the LOD of as low as 0.01 mg/L. The practical applicability of the method was demonstrated with the recovery in the range from 97 to 102% for inorganic arsenic, and 97 to 101% for organic arsenic. The method was applied to the analysis of commercial products from Nha Trang, Phan Thiet, and Phu Quoc City, Vietnam. The total organic arsenic in fish sauce samples determined by HG-AAS was compared with the results of liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP/MS). The f-test and t-test showed null hypothesis for acceptable variance and mean at a confidence level of 95%. The results showed that the HG-AAS method had high efficiency, accuracy, and sensitivity in quantifying inorganic and total organic arsenic in fish sauce using simple instrumentation.

A preliminary study of metal accumulation in fish from Cimanuk and Cimandiri, West Java, Indonesia

Fish is known to be a source of animal protein consisting of low cholesterol and non fatty acid. It also promotes sustainable consumption in coastal communities. Metal contamination in aquatic bodies, particularly rivers and oceans, is made more likely by anthropogenic factors. Metal may accumulate in fish as a result of the food web, posing a health risk to humans. Metal contamination in ingested fish should be monitored as part of risk mitigation. The goal of this research was to investigate six elements (Cr, Cu, Se, Pb, Cd, and As) in the edible tissues of fish from Cimanuk and Cimandiri, West Java. Karangsong and Palabuhan Ratu were two locus of fishing ports in Cimanuk and Cimandiri, respectively. In April of 2017, commercial demersal fish were obtained. Three fish from Palabuhan ratu and four fish from Karangsong were captured. Metal analysis was conducted using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP OES). The results revealed that the non-essential elements such as cadmium (Cd) and arsenic (As) had exceeded the permissible limits of the BPOM. Practically, organic arsenic (arsenobetain) is the most common arsenic found in fish (90-95%), and relatively safe compared to inorganic arsenic. Indications of Cd enrichment can come from anthropogenic factors and reinforce the necessity for environmental monitoring of habitats around fishing areas. Essential metals like selenium, copper, and chromium are maintained at a certain concentration based on metabolic activity and vary according to fish body homeostasis.

In-situ production and activation of H2O2 for enhanced degradation of roxarsone by FeS2 decorated resorcinol-formaldehyde resins

Fenton technology performs well in high-risk roxarsone (ROX) removal, but it is limited by the high H2O2 transportation and storage risks. Herein, FeS2 decorated resorcinol-formaldehyde resins (FeS2-RFR) were successfully prepared to in-situ produce and utilize H2O2 for efficient removal of ROX. Under solar light illumination, resorcinol-formaldehyde resins (RFR) efficiently generated a high concentration of H2O2, with a yield of 500 μmol g−1 h−1. FeS2 can in-situ decompose H2O2 to generate ·OH, participating in the oxidation of ROX. As a result, the FeS2-RFR catalyst degraded more than 97% of ROX within 2 h and ROX was selectively degraded into low-toxic As(V), which can be simply removed by traditional adsorption or precipitation processes. During the degradation of ROX, ·OH played a dominant role. Moreover, the cations (Na+, K+, and Ca2+), anions (SO42−, Cl−), and humic acid had no noticeable inhibition effect on ROX removal. Furthermore, FeS2-RFR can still remove 70% of ROX even after three cycles, proving that this in-situ photo-Fenton system exhibited stability. This study innovatively proposed a double-active site FeS2-RFR photocatalyst for in-situ production and activation of H2O2 and showed a sustainable and eco-friendly way for organoarsenic compounds degradation.

N-S co-doped TiO2 synthesized by microwave precipitation method: Effective photocatalytic performance for the removal of organoarsenic compounds

The N-S co-doped TiO2 (N-S/TiO2) photocatalyst was successfully prepared by microwave precipitation method using titanium oxysulfate and urea precursors. The material was characterized by XRD, UV-Vis diffuse reflectance spectroscopy, FTIR, SEM, TEM, N2 physisorption, elemental chemical analysis, photoluminescence (PL), and zetametry. The removal of p-arsanilic acid (p-ASA), and roxarsone (ROX) solution in a mixture at pH 9 under UV light (365 nm) evaluated the photocatalytic activity of N-S/ TiO2. The commercial TiO2 P25 was additionally assessed for comparative purposes. The N-S/TiO2 showed the anatase crystalline phase, mesoporous structure, and surface area of 27.1 m2/g. The N-S/TiO2 material presented surface hydroxyl groups, adsorbed NH3 species, and N and S impurities incorporated in an interstitial and substitutional way, respectively (0.54 and 6.74 wt. %). The non-metals doping into TiO2 extended the absorption spectra towards the visible region (λ = 409 nm) and produced defects that improved the adsorption and photocatalytic properties of the prepared catalyst. The N-S/TiO2 material exhibited a significantly enhanced activity than pure TiO2 P25 under UV and visible light. The N-S/TiO2 material resulted in the highest photocatalytic activity allowing the complete removal of p-ASA, and ROX species, 67% mineralization, and simultaneous adsorption of released inorganic arsenic (AsO43-, 96.2%) within 240 min. A decrease in the toxicity of the effluent evaluated by the in vitro Vibrio fischeri toxicity test was observed (13%) at the end of the reaction compared with its initial value (25%), evidencing the potential application of the photocatalytic treatment using N-S/TiO2 catalyst in the removal of phenylated arsenic compounds.

Adsorption of organic and inorganic arsenic from aqueous solution: Optimization, characterization and performance of Fe–Mn–Zr ternary magnetic sorbent

Arsenic is a highly toxic pollutant and exists in inorganic and organic forms in groundwater and industrial wastewater. It is of great importance to reduce the arsenic content to lower levels in the water (e.g., <10 ppb for drinking) in order to minimize risk to humans. In this study, a Fe–Mn–Zr ternary magnetic sorbent was fabricated via precipitation for removal of inorganic and organic arsenate. The synthesis of sorbent was optimized by Taguchi method, which leads to an adsorbent with higher adsorption capacity. The adsorption of As(V) was pH dependent; the optimal removal was achieved at pH 2 and 5 for inorganic and organic As(V), respectively. Contact time of 25 h was sufficient for complete adsorption of both inorganic and organic As(V). The adsorption isotherm study revealed that the adsorbent performed better in sequestration of inorganic As(V) than that of organic As(V); both adsorption followed the Langmuir isotherm with maximum adsorption capacities of 81.3 and 16.98 mg g−1 for inorganic and organic As(V), respectively. The existence of anions in the water had more profound effect on the adsorption of organic As(V) than the inorganic As(V). The co-existing silicate and phosphate ions caused significantly negative impacts on the adsorption of both As(V). Furthermore, the existence of humic acid caused the deterioration of inorganic As(V) removal but showed insignificant impact on the organic As(V) adsorption. The mechanism study demonstrated that ion exchange and complexation played key roles in arsenic removal. This study provides a promising magnetic adsorptive material for simultaneous removal of inorganic and organic As(V).

Distribution and speciation of arsenic in seasonally stratified reservoirs: Implications for biotransformation mechanisms governing interannual variability

HPLC-ICPMS was used to analyze the spatiotemporal variation of As species in different sections and tributaries of the Aha Reservoir over four seasons, and the migration and transformation mechanisms were clarified by combined analysis of hydrochemical parameters and microbial composition. The results showed that the internal release of As from the reservoir sediments is mainly due to the reduction of iron oxide and the release of adsorbed As(V). The average proportion of As(III) increased from 27.2% in autumn to 46.5% in summer, 68.9% in winter, and up to 70.8% in spring. In spring and summer, the high concentration of As(III) and organic arsenic in the epilimnion under phosphorus restriction was caused by the reductive metabolism of phytoplankton after intake of As(V). The arsenic species in the metalimnion were mainly affected by the oxidation-reduction potential (ORP). In summer and autumn, As-oxidizing bacteria used As(III) as an electron donor, and nitrate played an important role as an electron acceptor, maintaining the dominance of As(V) in the hypolimnion. However, in winter and spring, temperature-controlled ORP was the main process, which was dominated by As(III). In conclusion, As species show annual cycles in different layers of seasonally thermal stratified reservoirs. It provides a systematic mechanism of As species transformation in reservoirs, especially the effect of biological transformation mechanism.

Seasonal distribution of antibiotic resistance genes in the Yellow River water and tap water, and their potential transmission from water to human

The prevalence and transmission of antibiotic resistance genes (ARGs) and opportunistic pathogens in water environments can pose great threat to public health. However, the dissemination of ARGs and opportunistic pathogens from water environments to humans has been poorly explored. Here, we employed 16S rRNA gene sequencing and high-throughput quantitative PCR techniques to explore the seasonal distribution of ARGs and opportunistic pathogens in the Yellow River water (source water) and tap water, as well as their relationships with healthy humans at Lanzhou, China. Physiochemical analysis was applied to detect water quality parameters and heavy metal contents. The absolute abundance and diversity of ARGs in the Yellow River and tap water demonstrated distinct seasonal patterns. In winter, the Yellow river water had the highest ARG abundance and diversity, while tap water owned the lowest. Mobile genetic elements (MGEs) were the predominant driver of ARG profiles in both the Yellow river and tap water. Null model analysis showed that ARG assembly in the Yellow River was more influenced by stochastic processes than tap water and this was independent of seasons. Total organic carbon and arsenic contents exhibited positive correlations with many ARGs. Opportunistic pathogens Aeromonas and Pseudomonas may be potential hosts for ARGs. Approximately 80% of detected ARGs were shared between water samples and the human gut. These persistent ARGs could not be entirely eliminated through drinking water treatment processes. Thus, it is crucial to protect sources of tap water from anthropogenic pollution and improve water treatment technologies to reduce the dissemination of ARGs and ensure drinking-water biosafety for human health.

Arsenic contamination caused by roxarsone transformation with spatiotemporal variation of microbial community structure in a column experiment

Arsenic contamination from roxarsone in livestock manure is common, and livestock manure continuously accumulates in the open environment. Evaluations of the environmental processes of As mobilization and transformation are critical for predicting the fate of As compounds after roxarsone degradation. In this study, spatiotemporal variations in As species and microbial community structure were characterized using laboratory column experiments with background soil collected from Yanggu County (northern Shandong Plain, China), a region of intense poultry production. Organic and inorganic arsenic were detected by high-performance liquid chromatography (HPLC) and HPLC with hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS), respectively. High-throughput sequencing technology was used to describe microbial diversity. Results showed that roxarsone was transformed completely within 7 days, and As(Ⅲ) and As(Ⅴ) were the major degradation products. The concentration of As(Ⅲ) was much lower than that of As(Ⅴ). The As(Ⅲ) concentration increased significantly after Day 14, whereas the As(Ⅴ) concentration increased significantly after Day 84, indicating that As(Ⅲ) was initially produced. The microbial community structure changed significantly as roxarsone transformed into various As compounds. A critical and dominant bacterial strain, norank_f__Family_XVⅢ, was found to be related to the degradation of roxarsone into As(Ⅲ). This study improves our understanding of the fate of As species released from poultry litter to soil and groundwater, which is a threat to human health and environment.

Elemental Composition of Algae-Based Supplements by Energy Dispersive X-ray Fluorescence.

The aim of this study is to evaluate the elemental composition of fifteen algae-based supplements commonly sold in the Portuguese market, by energy dispersive X-ray fluorescence. Despite the fact that the majority of Kelp samples were a good source of iodine, the levels observed might well contribute to an excess in the human body, which can cause dysfunction of the thyroid gland. Furthermore, the presence of lead in Sea spaghetti, Arame, Hijiki and Wakame caused a considerable risk to public health vis a vis possible ingestion of a high daily dose. Regarding arsenic, great variability was observed in all the samples with concentrations equal to or above 60 μg/g in the case of Arame, KelpJ and Hijiki. Although algae mainly accumulate organic arsenic, some also contain high levels of its inorganic form, as is commonly pointed out for Hijiki. Thus, regular ingestion of these supplements must also take into account the mentioned facts. There is no doubt that these supplements are also good sources of other nutrients, but the lack of accurate regulations and control should alert consumers to avoid indiscriminate use of these types of products.

Efficient removal of roxarsone and emerging organic contaminants by a solar light-driven in-situ Fenton system

High-risk roxarsone (ROX) can be converted to highly toxic arsenite (As(III)) through biological and abiotic processes, which can cause severe arsenic contamination of water and crops. Traditional oxidation processes can only treat organic arsenic compounds instead of releasing inorganic arsenic (iAs). Herein, an Fe(II)/resorcinol formaldehyde resin (RF) solar light-driven in-situ Fenton system was applied to remove ROX and its released iAs. Under solar light illumination, RF can reduce oxygen to produce H2O2 through a two-electron reduction pathway. Fe(II) simultaneously catalyzed the decomposition of H2O2 to generate ·OH, participating in the oxidation of ROX. The C-As bond of ROX was preferentially attacked by ·OH to form 2-nitrohydroquinone and As(III). Moreover, As(III) was further converted to low-toxicity arsenate (As(V)) through further oxidation with oxygen bubbling. Finally, the released As(III) (1.9%) and As(V) (98.1%) were removed by adsorption onto the surface of ferric hydroxide. As a result, more than 99.9% of ROX was degraded by the Fe(II)/RF in-situ Fenton system during the pre-oxidation process. The total organic carbon (TOC) removal efficiency of ROX and total arsenic removal efficiency of the Fe(II)/RF-O2 in-situ Fenton system reached 75% and more than 97%, respectively. Furthermore, the residual arsenic in this Fenton system was less than 12.5 µg/L, which met the recommended limit for arsenic (100 µg/L) in reclaimed water. In addition to the removal of ROX, the Fe(II)/RF in-situ Fenton system showed excellent general applicability in the removal of emerging organic contaminants (EOCs). The TOC removal rate of EOCs was approximately 50%–64%. Thus, the Fe(II)/RF-O2 solar light-driven in-situ Fenton system provides a novel strategy for the high-efficiency removal of organoarsenic compounds and EOCs.