Arsenic and antimony: comparative approach on mechanistic toxicology

Development of an efficient electrochemical sensing platform based on ter-poly(luminol-o-anisidine-o-toluidine)/ZnO/GNPs nanocomposites for the detection of antimony (Sb3+) ions

A poly(luminol-o-anisidine-o-toluidine) terpolymer was synthesized, characterized, and modified with GNPs and ZnO NPs. The nanocomposites were then examined for their electroactivity and potential use as cationic electrochemical sensors for detecting Sb3+ ions in phosphate buffer on the surface of a glassy carbon electrode (GCE). Among the different compositions and the terpolymer, the GCE adapted with the PLAT/ZnO/GNPs-5% nanocomposite displayed the highest current response. The fabricated nanocomposite sensor exhibited high sensitivity, with a value of 21.4177 μA μM-1 cm-2, and a low detection limit of 95.42 pM. The analytical performance of the sensor was evaluated over the linear dynamic range (LDR) of 0.1 nM to 0.01 mM. The proposed sensor is effective in detecting and measuring carcinogenic Sb3+ ions in real environmental samples using an electrochemical approach, making it a promising tool for environmental monitoring.

Arsenic and antimony desorption in water treatment processes: Scaling up challenges with emerging adsorbents

The metalloids arsenic (As) and antimony (Sb) belong to the pnictogen group of the periodic table; they share many characteristics, including their toxic and carcinogenic properties; and rank as high-priority pollutants in the United States and the European Union. Adsorption is one of the most effective techniques for removing both elements and desorption, for further reuse, is a part of the process to make adsorption more sustainable and feasible. This review presents the current state of knowledge on arsenic and antimony desorption from exhausted adsorbents previously used in water treatment, that has been reported in the literature. The application of different types of eluents to desorb As and Sb and their desorption performance are described. The regeneration of saturated adsorbents and adsorbate recovery techniques are outlined, including the fate of spent media and possible alternatives for waste disposal of exhausted materials. Future research directions are discussed, as well as current issues including the lack of environmental impact analysis of emerging adsorbents.

Selective pressure of arsenic and antimony co-contamination on microbial community in alkaline sediments

Although response of microbial community to arsenic (As) and antimony (Sb) co-contamination has been investigated in neutral and acidic environments, little is known in alkaline environment. Herein, the microbial response and survival strategies under the stress of As and Sb co-contamination were determined in the alkaline sediments. Elevated concentrations of As (13700 ± 5012 mg/kg) and Sb (10222 ± 1619 mg/kg) were introduced into the alkaline sediments by the mine drainage, which was partially adopted in the aquatic environment and resulted in a relatively lower contamination (As, 6633 ± 1707 mg/kg; Sb, 6108 ± 1095 mg/kg) in the downstream sediments. The microbial richness was significantly damaged and the microbial compositions were dramatically shifted by the As and Sb co-contamination. Metagenomic analysis shed light on the survival strategies of the microbes under the pressure of As and Sb co-contamination including metal oxidation coupled with denitrification, metal reduction, and metal resistance. The representative microbes were revealed in the sediments with higher (Halomonas) and lower (Thiobacillus, Hydrogenophaga and Flavihumibacter) As and Sb concentration, respectively. In addition, antibiotic resistance genes were found to co-occur with metal resistance genes in the assembled bins. These findings might provide theoretical guidance for bioremediation of As and Sb co-contamination in alkaline environment.

Characterization of an antimony-resistant fungus Sarocladium kiliense ZJ-1 and its potential as an antimony bio-remediator

Antimony (Sb) is a toxic metalloid widely distributed in the natural environments. Microorganisms, especially fungi, could serve as ideal biomaterials for bioremediation of Sb-polluted soils and waters. In this study, we isolated an antimony-resistant fungus, Sarocladium kiliense ZJ-1, from a slag sample collected in Xikuangshan Sb mine in P. R. China. ZJ-1 showed an extremely high resistance to Sb, with a MIC level of > 175 mM for arsenite [Sb(Ⅲ)] and 40 mM for arsenate [Sb(V)]. Whole genomic analysis identified multiple Sb (Ⅲ)- and/or As(Ⅲ)-resistant genes on ZJ-1's genome, which may partially explain its hyper-resistance to Sb. The potential of ZJ-1 in removing Sb from Sb(Ⅲ) or Sb(V) solutions was also quantified. The average biosorption capacity of ZJ-1 for Sb(Ⅲ) and Sb(V) is 635.14 mg/g and 149.65 mg/g, respectively, in Sb aqueous solutions with an initial concentration of 2000 mg/L (16.43 mM). Besides, almost 99% of Sb(Ⅲ) in the growing system was removed with an initial concentration of 500 mg/L (4.11 mM). Furthermore, Fourier transformation infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) were used to probe the Sb adsorption mechanism on ZJ-1, and -OH, -NH2, -COOH, C-O and C-O-C were found to be the main surface functional groups of ZJ-1 cells to adsorb Sb.

Oxidation of Sb(III) by Shewanella species with the assistance of extracellular organic matter

Antimony (Sb) is a toxic substance that poses a serious ecological threat when released into the environment. The species and redox state of Sb determine its environmental toxicity and fate. Understanding the redox transformations and biogeochemical cycling of Sb is crucial for analyzing and predicting its environmental behavior. Dissolved organic matter (DOM) in the environment greatly affects the fate of Sb. Microbially produced DOM is a vital component of environmental DOM; however, its specific role in Sb(III) oxidation has not been experimentally confirmed. In this work, the oxidation capacity of several Shewanella strains and their derived DOM to Sb(III) was confirmed. The oxidation rate of Sb(III) shows a positive correlation with DOM concentration, with higher rates observed under neutral and weak alkaline conditions, regardless of the presence of light. Incubation experiments indicated that extracellular enzymes and common reactive oxygen species were not involved in the oxidation of Sb(III). Characteristics of DOM suggests that microbial humic acid-like and fulvic acid-like substances are the potential contributors to Sb(III) oxidation. These findings not only experimentally validate the role of bacterial-derived DOM in Sb(III) oxidation but also reveal the significance of Shewanella and biogenic DOM in the biogeochemical cycling of Sb.

Urine antimony and risk of cardiovascular disease - A prospective case-cohort study in Danish Non-Smokers

BACKGROUND

Limited evidence suggests that antimony induces vascular inflammation and oxidative stress and may play a role in cardiovascular disease (CVD) risk. However, few studies have examined whether environmental antimony from sources other than tobacco smoking is related with CVD risk. The general population may be exposed through air, drinking water, and food that contains antimony from natural and anthropogenic sources, such as mining, coal combustion, and manufacturing.

OBJECTIVES

To examine the association of urine antimony with incident acute myocardial infarction (AMI), heart failure, and stroke among people who never smoked tobacco.

METHODS

Between 1993 and 1997, the Danish Diet, Cancer and Health (DCH) cohort enrolled participants (ages 50-64 years), including n = 19,394 participants who reported never smoking at baseline. Among these never smokers, we identified incident cases of AMI (N = 809), heart failure (N = 958), and stroke (N = 534) using the Danish National Patient Registry. We also randomly selected a subcohort of 600 men and 600 women. We quantified urine antimony concentrations in samples provided at enrollment. We used modified Cox proportional hazards models to estimate adjusted hazard ratios (HR) for each incident CVD outcome in relation to urine antimony, statistically adjusted for creatinine. We used a separate prospective cohort, the San Luis Valley Diabetes Study (SLVDS), to replicate these results.

RESULTS

In the DCH cohort, urine antimony concentrations were positively associated with rates of AMI and heart failure (HR = 1.52; 95%CI = 1.12, 2.08 and HR = 1.58; 95% CI = 1.15, 2.18, respectively, comparing participants in the highest (>0.09 µg/L) with the lowest quartile (<0.02 µg/L) of antimony). In the SLVDS cohort, urinary antimony was positively associated with AMI, but not heart failure.

DISCUSSION

Among this sample of Danish people who never smoked, we found that low levels of urine antimony are associated with incident CVD. These results were partially confirmed in a smaller US cohort.

Maternal hair segments reveal metal(loid) levels over the course of pregnancy: a preliminary study in Southern China

Characterization of metal(loid) variation during pregnancy and identification of the affecting factors are important for assessing pregnancy exposures in epidemiological studies. In this study, maternal hair was collected in three segments (each 3 cm) from pregnant women in Guangzhou, China. Ten metal(loid)s, including six essential trace metal(loid)s and four toxic trace metal(loid)s, were analyzed to investigate the levels of various metal(loid)s during pregnancy and the factors that influence them. Strong pairwise correlations were observed between manganese (Mn), cobalt (Co), and vanadium (V), between selenium (Se), arsenic (As), and antimony (Sb), and between cadmium (Cd) and lead (Pb). All metal(loid)s except for Se, Mn, and Co showed strong correlations among the three hair segments, and most of the metal(loid)s had good reproducibility, with intraclass correlation coefficients (ICCs) ranging from 0.510 to 0.931, except for As (ICC = 0.334), Mn (ICC = 0.231), and Co (ICC = 0.235). Zn levels decreased, while Sb increased, in maternal hair during pregnancy. Maternal sociodemographic characteristics and dietary intake affected metal(loid) levels in maternal hair. These results provide foundational data for using maternal hair segmental analysis to evaluate exposure variation to metal(loid)s during pregnancy and the potential factors associated with them.

Widespread Distribution of the arsO Gene Confers Bacterial Resistance to Environmental Antimony

Microbial oxidation of environmental antimonite (Sb(III)) to antimonate (Sb(V)) is an antimony (Sb) detoxification mechanism. Ensifer adhaerens ST2, a bacterial isolate from a Sb-contaminated paddy soil, oxidizes Sb(III) to Sb(V) under oxic conditions by an unknown mechanism. Genomic analysis of ST2 reveals a gene of unknown function in an arsenic resistance (ars) operon that we term arsO. The transcription level of arsO was significantly upregulated by the addition of Sb(III). ArsO is predicted to be a flavoprotein monooxygenase but shows low sequence similarity to other flavoprotein monooxygenases. Expression of arsO in the arsenic-hypersensitive Escherichia coli strain AW3110Δars conferred increased resistance to Sb(III) but not arsenite (As(III)) or methylarsenite (MAs(III)). Purified ArsO catalyzes Sb(III) oxidation to Sb(V) with NADPH or NADH as the electron donor but does not oxidize As(III) or MAs(III). The purified enzyme contains flavin adenine dinucleotide (FAD) at a ratio of 0.62 mol of FAD/mol protein, and enzymatic activity was increased by addition of FAD. Bioinformatic analyses show that arsO genes are widely distributed in metagenomes from different environments and are particularly abundant in environments affected by human activities. This study demonstrates that ArsO is an environmental Sb(III) oxidase that plays a significant role in the detoxification of Sb(III).

Antimony(III) removal by biogenic manganese oxides formed by Pseudomonas aeruginosa PA-1: kinetics and mechanisms

In this study, Pseudomonas aeruginosa PA-1, a manganese-oxidizing bacterium screened from the soil at a manganese mining area, was found to be tolerated to Sb(III) stress during the Mn(II) oxidation, and the generated biological manganese oxide (BMO) outperformed the identical type of Abiotic-MnOX in terms of oxidation and adsorption of Sb(III). Adsorption kinetics and isotherm experiments indicated that Sb(III) was primarily adsorbed through chemisorption and multilayer adsorption on BMO; the maximum adsorption capacity of BMO was 143.15 mg·g-1. Removal kinetic studies showed that the Sb(III) removal efficiency by BMO was 72.38-95.71% after 15 min, and it could be up to 96.32-98.31% after 480 min. The removal procedure could be divided into two stages, fast (within 15 min) and slow (15 ~ 480 min), both of which exhibited first-order kinetic behavior. Dynamic fitting in two steps revealed that the removal speed correlated to the level of dissolved Sb(III) with low Sb(III) concentrations, but with the initial concentration being high, the removal speed rate was independent of dissolved Sb(III). During the whole process, the Sb(III) removal speed by BMO was also higher than that by the Abiotic-MnOX. Combining multiple spectroscopic techniques revealed that Sb(V) was generated through the Sb(III) oxidation by BMO and replacing surface metal hydroxyl groups to form the complex internal Mn-O(H)-Sb(V) or generating stable Mn(II)-antimonate precipitates on the surface. In addition, microbial metabolites, including tryptophan and humus, in BMO may be complex with Sb(III) and Sb(V) to achieve the treatment of Sb(III). This research investigates the factors and mechanisms influencing the adsorption and removal of Sb(III) by BMO, which could aid in its future engineering applications for the BMO.

Occurrences, sources and health hazard estimation of potentially toxic elements in the groundwater of Garhwal Himalaya, India

High concentrations of potentially toxic elements (PTEs) in potable water can cause severe human health disorders. Present study examined the fitness of groundwater for drinking purpose based on the occurrence of nine PTEs in a heavy pilgrim and tourist influx region of the Garhwal Himalaya, India. The concentrations of analyzed PTEs in groundwater were observed in the order of Zn > Mn > As > Al > Cu > Cr > Se > Pb > Cd. Apart from Mn and As, other PTEs were within the corresponding guideline values. Spatial maps were produced to visualize the distribution of the PTEs in the area. Estimated water pollution indices and non-carcinogenic risk indicated that the investigated groundwater is safe for drinking purpose, as the hazard index was < 1 for all the water samples. Assessment of the cancer risk of Cr, As, Cd, and Pb also indicated low health risks associated with groundwater use, as the values were within the acceptable range of ≤ 1 × 10-6 to 1 × 10-4. Multivariate statistical analyses were used to describe the various possible geogenic and anthropogenic sources of the PTEs in the groundwater resources although the contamination levels of the PTEs were found to pose no serious health risk. However, the present study recommends to stop the discharge of untreated wastewater and also to establish cost-effective as well as efficient water treatment facility nearby the study area. Present work's findings are vital as they may protect the health of the massive population from contaminated water consumption. Moreover, it can help the researchers, governing authorities and water supplying agencies to take prompt and appropriate decisions for water security.

Distribution, Metabolism, and Toxicity of Antimony Species in Wistar Rats. A Bio-Analytical Approach

This work studied the distribution, reactivity, and biological effects of pentavalent or trivalent antimony (Sb(V), Sb(III)) and N-methylglucamine antimonate (NMG-Sb(V)) in Wistar Rats. The expression of fibrosis genes such as α-SMA, PAI-1, and CTGF were determined in Liver, and Kidney tissues. Wistar rats were treated with different concentrations of Sb(V), Sb(III), As(V) and As(III), and MA via intra-peritoneal injections. The results indicated a noteworthy elevation in mRNA levels of plasminogen activator 1 (PAI-1) in the kidneys of rats that were injected. The main accumulation site for Sb(V) was observed to be the liver, from which it is primarily excreted in its reduced form (Sb(III)) through the urine. The generation of Sb(III) in the kidneys has been found to induce damage through the expression of α-SMA and CTGF, and also lead to a higher creatinine clearance compared to As(III).

Responses of potential ammonia oxidation and ammonia oxidizers community to arsenic stress in seven types of soil

Soil arsenic contamination is of great concern because of its toxicity to human, crops, and soil microorganisms. However, the impacts of arsenic on soil ammonia oxidizers communities remain unclear. Seven types of soil spiked with 0 or 100 mg arsenic per kg soil were incubated for 180 days and sampled at days 1, 15, 30, 90 and 180. The changes in the community composition and abundance of ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) were analyzed by terminal restriction fragment length polymorphism (T-RFLP) analysis, clone library sequencing, and quantitative PCR (qPCR) targeting amoA gene. Results revealed considerable variations in the potential ammonia oxidation (PAO) rates in different soils, but soil PAO was not consistently significantly inhibited by arsenic, probably due to the low bioavailable arsenic contents or the existence of functional redundancy between AOB and AOA. The variations in AOB and AOA communities were closely associated with the changes in arsenic fractionations. The amoA gene abundances of AOA increased after arsenic addition, whereas AOB decreased, which corroborated the notion that AOA and AOB might occupy different niches in arsenic-contaminated soils. Phylogenetic analysis of amoA gene-encoded proteins revealed that all AOB clone sequences belonged to the genus Nitrosospira, among which those belonging to Nitrosospira cluster 3a were dominant. The main AOA sequence detected belonged to Thaumarchaeal Group 1.1b, which was considered to have a high ability to adapt to environmental changes. Our results provide new insights into the impacts of arsenic on the soil nitrogen cycling.

Microbial Reduction of Antimony(V)-Bearing Ferrihydrite by Geobacter sulfurreducens

The reduction of Sb(V)-bearing ferrihydrite by Geobacter sulfurreducens was studied to determine the fate of the metalloid in Fe-rich systems undergoing redox transformations. Sb(V) added at a range of concentrations adsorbed readily to ferrihydrite, and the loadings had a pronounced impact on the rate and extent of Fe(III) reduction and the products formed. Magnetite dominated at low (0.5 and 1 mol%) Sb(V) concentrations, with crystallite sizes decreasing at higher Sb loadings: 37-, 25-, and 17-nm particles for no-Sb, 0.5% Sb, and 1% Sb samples, respectively. In contrast, goethite was the dominant end product for samples with higher antimony loadings (2 and 5 mol%), with increased goethite grain size in the 5% Sb sample. Inductively coupled mass spectrometry (ICP-MS) analysis confirmed that Sb was not released to solution during the bioreduction process, and X-ray photoelectron spectroscopy (XPS) analyses showed that no Sb(III) was formed throughout the experiments, confirming that the Fe(III)-reducing bacterium Geobacter sulfurreducens cannot reduce Sb(V) enzymatically or via biogenic Fe(II). These findings suggest that Fe (bio)minerals have a potential role in limiting antimony pollution in the environment, even when undergoing redox transformations. IMPORTANCE Antimony is an emerging contaminant that shares chemical characteristics with arsenic. Metal-reducing bacteria (such as Geobacter sulfurreducens) can cause the mobilization of arsenic from Fe(III) minerals under anaerobic conditions, causing widespread contamination of aquifers worldwide. This research explores whether metal-reducing bacteria can drive the mobilization of antimony under similar conditions. In this study, we show that G. sulfurreducens cannot reduce Sb(V) directly or cause Sb release during the bioreduction of the Fe(III) mineral ferrihydrite [although the sorbed Sb(V) did alter the Fe(II) mineral end products formed]. Overall, this study highlights the tight associations between Fe and Sb in environmental systems, suggesting that the microbial reduction of Fe(III)/Sb mineral assemblages may not lead to Sb release (in stark contrast to the mobilization of As in iron-rich systems) and offers potential Fe-based remediation options for Sb-contaminated environments.

A molecular level understanding of antimony immobilization mechanism on goethite by the combination of X-ray absorption spectroscopy and density functional theory calculations

A molecular level understanding of antimony (Sb) immobilization mechanism on Fe oxides is required to clarify the fate of Sb in the soil. In this study, macroscopic sorption experiments, combined with extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT), were utilized to explore the interaction between Sb and goethite. The ion strength has no effect on Sb sorption on goethite, indicating the inner-sphere complex Sb formed on goethite. Goethite has the higher sorption potential to Sb(III) than Sb(V), consistent with the higher thermodynamic stability of the geometry for Sb(III) formed on goethite than Sb(V) revealed by DFT calculations. By comparing the Sb-Fe distances obtained by EXAFS spectroscopy and DFT, eight kinds of Sb(III) surface complexes and nine kinds of Sb(V) surface complexes were considered to be the possible geometries Sb formed on different crystal planes of goethite, including monodentate mononuclear, bidentate mononuclear, bidentate binuclear, tridentate mononuclear, tridentate binuclear, tridentate four-nuclear complexes. The structural and energetic details of these filtered geometries provide comprehensive information on Sb immobilization mechanism on goethite, helpful in clarifying the fate of Sb in soils.

Silicon Actuates Poplar Calli Tolerance after Longer Exposure to Antimony

The presence of antimony (Sb) in high concentrations in the environment is recognized as an emerging problem worldwide. The toxicity of Sb in plant tissues is known; however, new methods of plant tolerance improvement must be addressed. Here, poplar callus (Populus alba L. var. pyramidallis) exposed to Sb(III) in 0.2 mM concentration and/or to silicon (Si) in 5 mM concentration was cultivated in vitro to determine the impact of Sb/Si interaction in the tissue. The Sb and Si uptake, growth, the activity of superoxide dismutase (SOD), catalase (CAT), guaiacol-peroxidase (G-POX), nutrient concentrations, and the concentrations of photosynthetic pigments were investigated. To elucidate the action of Si during the Sb-induced stress, the impact of short and long cultivations was determined. Silicon decreased the accumulation of Sb in the calli, regardless of the length of the cultivation (by approx. 34%). Antimony lowered the callus biomass (by approx. 37%) and decreased the concentrations of photosynthetic pigments (up to 78.5%) and nutrients in the tissue (up to 21.7%). Silicon supported the plant tolerance to Sb via the modification of antioxidant enzyme activity, which resulted in higher biomass production (increased by approx. 35%) and a higher uptake of nutrients from the media (increased by approx. 10%). Silicon aided the development of Sb-tolerance over the longer cultivation period. These results are key in understanding the action of Si-developed tolerance against metalloids.

Speciation, in vitro bioaccessibility and health risk of antimony in soils near an old industrial area

Antimony (Sb) contamination in soil has become a major environmental issue due to its adverse effects on ecosystems and human health. In this paper, 1255 soil samples were analyzed to investigate the distribution, speciation, in vitro oral bioaccessibility (8 soil samples) and human health risk of Sb in contaminated soils and its impacts on groundwater. The results showed that 4.38 % of the soil samples within the depth of 0-31 m exceeded the Risk Screening Values (RSV). Sb mainly existed in the residual fraction (38.05 % ∼ 94.22 %), Fe/Mn oxides (0.01 % ∼ 31.80 %) and the organic fraction (0.32 % ∼ 21.55 %) with poor mobility. The bioaccessibility of Sb was approximately <31 %. The total concentration of Sb (TSb) in soil was the dominant factor influencing the bioaccessible concentration of Sb (SbBio). Soil physiochemical properties such as Fe, Mn, and organic matter content (OM) also affected the magnitude of SbBio. Health risk assessment based on in vitro bioaccessibility suggested that the hazard quotient (HQ) of adults was within the acceptable level (HQ < 1) for industrial scenario, while the HQ of children and adults was greater than the acceptable level (HQ ≥ 1) for residential scenario, with a higher risk to children than adults. The results of the leaching experiment involving Dilution-Attenuation Factor (DAF) model suggested that the predicted maximum concentration of Sb in groundwater was 2.40 μg/L that is lower than the acceptable standard value (5 μg/L), implying that groundwater was not contaminated by Sb in soil. The findings of this study provide some insights into the speciation, in vitro bioaccessibility and health risk of toxic trace metals in contaminated soils and the potential environmental impacts.

Evaluation of Pollution Level, Spatial Distribution, and Ecological Effects of Antimony in Soils of Mining Areas: A Review

The first global-scale assessment of Sb contamination in soil that was related to mining/smelting activities was conducted based on 91 articles that were published between 1989 and 2021. The geographical variation, the pollution level, the speciation, the influencing factors, and the environmental effects of Sb that were associated with mining/smelting-affected soils were analyzed. The high Sb values mainly occurred in developed (Poland, Italy, Spain, Portugal, New Zealand, Australia) and developing (China, Algeria, Slovakia) countries. Sb concentrations of polluted soil from mining areas that were reported in most countries significantly exceeded the maximum permissible limit that is recommended by WHO, except in Turkey and Macedonia. The soil Sb concentrations decreased in the order of Oceania (29,151 mg/kg) > North Africa (13,022 mg/kg) > Asia (1527 mg/kg) > Europe (858 mg/kg) > South America (37.4 mg/kg). The existing extraction methods for Sb speciation have been classified according to the extractant, however, further research is needed in the standardization of these extraction methods. Modern analytical and characterization technologies, e.g., X-ray absorption spectroscopy, are effective at characterizing chemical speciation. Conditional inference tree (CIT) analysis has shown that the clay content was the major factor that influenced the soil Sb concentration. Non-carcinogenic risks to the public from soil Sb pollution were within the acceptable levels in most regions. An Sb smelter site at the Endeavour Inlet in New Zealand, an abandoned open-pit Sb mine in Djebel Hamimat, Algeria, an old Sb-mining area in Tuscany, Italy, and Hillgrove mine in Australia were selected as the priority control areas. Cynodon dactylon, Boehmeria, Pteris vittata, and Amaranthus paniculatus were found to be potential Sb accumulators. All of the values of bioaccumulation factors for the crops were less than one. However, ingestion of Sb through crop consumption posed potential non-carcinogenic health risks, which should not be neglected. The soil variables (pH, Eh, total sulfur, carbon nitrogen ratio, total organic carbon, and sulfate), the total Sb and the bioavailable Sb, and heavy metal(loid)s (As, Pb, and Fe) were the major parameters affecting the microbial community compositions.

The leaching of antimony and arsenic by simulated acid rain in three soil types from the world's largest antimony mine area

A simulated acid rain (SAR) experiment on leaching of antimony (Sb) and arsenic (As) in three soil types including paddy soils (PS), vegetable soils (VS) and slag based soils (SS) from Xikuangshan (XKS) Sb mine area was conducted. The SAR at pH 2.5, 3.5, 4.5 and 5.6 were sprayed to soil columns with intermittent pattern in a period of 50 days. Through the spraying duration, leaching Sb in PS, VS and SS showed decreasing trends regardless of pH values in SAR and were in the ranges of 0.026-0.064 mg L^-1, 0.19-2.18 mg L^-1 and 11.8-32.4 mg L^-1, respectively. By contrast, leaching As in these three soil types continuously increased at the initial five spraying times and then deeply decreased afterward, with ranges being 0-0.007 mg L^-1, 0.001-0.071 mg L^-1 and 0.17-1.07 mg L^-1, respectively. The leaching Sb in all the three soil types were extremely higher than the reference value in grade IV (0.01 mg L^-1) for groundwater quality of China (GB/T 14,848-2017). For leaching As, peck values in VS and all the values in SS were also greater than the corresponding reference value (0.05 mg L^-1). This indicated that leaching Sb and As could pollute the groundwater in XKS Sb mine area, especially those in slag based soils. The total leaching losses of Sb and As were affected by pH ambiguously, such as SAR at pH 2.5, 5.6 and 2.5 induced the greatest losses of Sb in PS, VS and SS, and pH 3.5, 5.6 and 2.5 resulted in the greatest leaching losses of As in these soils. After SAR treatment, the specific sorbed and Fe/Mn oxide-associated Sb and As significantly decreased. It demonstrated that these two fractions of both Sb and As were involved in leaching losses. The present study also found that the SAR treatment resulted in soil acidification in all the three soil types. In addition, available N, P and K in all the SAR treatments decreased regardless of pH values, except for available N and P in PS.

4-Chloro-1,2-phenylenediamine induced structural perturbation and genotoxic aggregation in human serum albumin

4-Chloro-1,2-phenylenediamine (4-Cl-OPD) is a halogenated aromatic diamine used as a precursor in permanent hair color production. Despite its well-documented mutagenic and carcinogenic effects in various in vitro and in vivo models, its role in fibrillar aggregate formation and their genotoxic effect in therapeutic proteins has received less attention. The significance of human serum albumin (HSA) arises from its involvement in bio-regulatory and transport processes. HSA misfolding and aggregation are responsible for some of the most frequent neurodegenerative disorders. We used various complementary approaches to track the formation of amyloid fibrils and their genotoxic effect. Molecular dynamics study demonstrated the complex stability. The impact of 4-Cl-OPD on the structural dynamics of HSA was confirmed by Raman spectroscopy, X-ray diffraction, HPLC and SDS-PAGE. Fibrilllar aggregates were investigated using Congo red assay, DLS, and SEM. The genotoxic nature of 4-Cl-OPD was confirmed using plasmid nicking assay and DAPI staining, which revealed DNA damage and cell apoptosis. 4-Cl-OPD provides a model system for studying fibrillar aggregation and their genotoxic potential in the current investigation. Future studies should investigate the inhibition of the aggregation/fibrillation process, which may yield valuable clinical insights.

Microbial community structures and their driving factors in a typical gathering area of antimony mining and smelting in South China

This study investigated soil microbial community in a typical gathering area of antimony mining and smelting in South China. The physical and chemical properties of different soils (mining waste dumps, flotation tailings, and smelting slag) and depths (0-20 cm, 40-60 cm, and 80-100 cm) were compared. The results showed that antimony (Sb) and arsenic (As) were the main pollutants, and their concentrations were 5524.7 mg/kg and 3433.7 mg/kg, respectively. Xanthates were found in the flotation tailings and smelting slag, and the highest concentration was 585.1 mg/kg. The microbial communities were analyzed by high-throughput sequencing, and it was shown that Proteobacteria, Acidobacteria, Chlorobacterium, Bacteroides, and Actinomycetes were the dominant taxa at the phylum level. There were obvious differences in microbial community structure in different sites. The dominant microorganism in the mining site was Chujaibacter. Subgroup_2_unclassified and Gemmatimonadaceae_unclassified were the prevalent microorganisms in the flotation and smelting sites, respectively. As, Sb, and xanthates were the main factors affecting the diversity and composition of bacteria in the flotation tailings and smelting slag areas. Therefore, this study provides experimental guidance and a theoretical basis for soil antimony pollution quality assessment, biological treatment, and environmental remediation.

Antimony redox processes in the environment: A critical review of associated oxidants and reductants

The environmental behavior of antimony (Sb) has recently received greater attention due to the increasing global use of Sb in a range of industrial applications. Although present at trace levels in most natural systems, elevated Sb concentrations in aquatic and terrestrial environments may result from anthropogenic activities. The mobility and toxicity of Sb largely depend on its speciation, which is dependent to a large extent on its oxidation state. To a certain extent, our understanding of the environmental behavior of Sb has been informed by studies of the environmental behavior of arsenic (As), as Sb and As have somewhat similar chemical properties. However, recently it has become evident that the speciation of Sb and As, especially in the context of redox reactions, may be fundamentally different. Therefore, it is crucial to study the biogeochemical processes impacting Sb redox transformations to understand the behavior of Sb in natural and engineered environments. Currently, there is a growing body of literature involving the speciation, mobility, toxicity, and remediation of Sb, and several reviews on these general topics are available; however, a comprehensive review focused on Sb environmental redox chemistry is lacking. This paper provides a review of research conducted within the past two decades examining the redox chemistry of Sb in aquatic and terrestrial environments and identifies knowledge gaps that need to be addressed to develop a better understanding of Sb biogeochemistry for improved management of Sb in natural and engineered systems.

Desulfurivibrio spp. mediate sulfur-oxidation coupled to Sb(V) reduction, a novel biogeochemical process

Antimony (Sb) contamination released from mine tailings represents a global threat to natural ecosystems and human health. The geochemical conditions of Sb tailings, which are oligotrophic and replete in sulfur (S) and Sb, may promote the coupled metabolism of Sb and S. In this study, multiple lines of evidence indicate that a novel biogeochemical process, S oxidation coupled to Sb(V) reduction, is enzymatically mediated by Desulfurivibrio spp. The distribution of Desulfurivibrio covaried with S and Sb concentrations, showing a high relative abundance in Sb mine tailings but not in samples from surrounding sites (i.e., soils, paddies, and river sediments). Further, the metabolic potential to couple S oxidation to Sb(V) reduction, encoded by a non-canonical, oxidative sulfite reductase (dsr) and arsenate reductase (arrA) or antimonate reductase (anrA), respectively, was found to be common in Desulfurivibrio genomes retrieved from metal-contaminated sites in southern China. Elucidation of enzymatically-catalyzed S oxidation coupled to Sb(V) reduction expands the fundamental understanding of Sb biogeochemical cycling, which may be harnessed to improve remediation strategies for Sb mine tailings.

“For Asia Market Only”: A Green Tattoo Ink between Safety and Regulations

Due to the increasing tattoo practicing in Eastern countries and general concern on tattoo ink composition and safety, the green tattoo inks Green Concentrate by Eternal, for European and “for Asia Market Only” were analyzed, under the premise that only the former falls under a composition regulation. A separation of the additives from the pigment was carried out by successive extraction in solvents of different polarities, i.e., water, acetone and dichloromethane. The solid residues were analyzed by IR and Raman spectroscopies, the liquid fractions by GC/mass spectrometry. The relative pigment load and element traces were also estimated. We found that the European and the Asian inks are based on the same pigment, PG7, restricted in Europe, though at different loads. They have a similar content of harmful impurities, such as Ni, As, Cd and Sb and both contain siloxanes, including harmful D4. Furthermore, they have different physical-chemical properties, the European ink being more hydrophilic, the Asian more hydrophobic. Additionally, the Asian ink contains harmful additives for the solubilization of hydrophobic matrices and by-products of the phthalocyanine synthesis. Teratogenic phthalates are present as well as chlorinated teratogenic and carcinogenic compounds usually associated to the laser treatment for removal purposes, to a larger extent in the European ink. The composition of the inks does not seem to reflect regulatory restrictions, where issued.

Role of Environmental Toxicants on Neurodegenerative Disorders

Neurodegeneration leads to the loss of structural and functioning components of neurons over time. Various studies have related neurodegeneration to a number of degenerative disorders. Neurological repercussions of neurodegeneration can have severe impacts on the physical and mental health of patients. In the recent past, various neurodegenerative ailments such as Alzheimer’s and Parkinson’s illnesses have received global consideration owing to their global occurrence. Environmental attributes have been regarded as the main contributors to neural dysfunction-related disorders. The majority of neurological diseases are mainly related to prenatal and postnatal exposure to industrially produced environmental toxins. Some neurotoxic metals, like lead (Pb), aluminium (Al), Mercury (Hg), manganese (Mn), cadmium (Cd), and arsenic (As), and also pesticides and metal-based nanoparticles, have been implicated in Parkinson’s and Alzheimer’s disease. The contaminants are known for their ability to produce senile or amyloid plaques and neurofibrillary tangles (NFTs), which are the key features of these neurological dysfunctions. Besides, solvent exposure is also a significant contributor to neurological diseases. This study recapitulates the role of environmental neurotoxins on neurodegeneration with special emphasis on major neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease.

Migration and transformation of Sb are affected by Mn(III/IV) associated with lepidocrocite originating from Fe(II) oxidation

Antimony (Sb) is a recognized priority pollutant with toxicity that is influenced by its migration and transformation processes. Oxidation of Fe(II) to Fe(III) oxides, which is a common phenomenon in the environment, is often accompanied by the formation of Mn(III/IV) and might affect the fate of Sb. In this study, incorporated Mn(III) and sorbed/precipitated Mn(III/IV) associated with lepidocrocite were prepared by adding Mn(II) during and after Fe(II) oxidation, respectively, and the effects of these Mn species on Sb fate were investigated. Our results indicated that the association of these Mn species with lepidocrocite obviously enhanced Sb(III) oxidation to Sb(V), while concomitantly inhibiting Sb sorption due to the lower sorption capacity of lepidocrocite for Sb(V) than Sb(III). Additionally, Mn oxide equivalents increased in the presence of Sb, indicating that Sb oxidation by Mn(III/IV) associated with lepidocrocite was a continuous recycling process in which Mn(II) released from Mn(III/IV) reduction by Sb(III) could be oxidized to Mn(III/IV) again. This recycling process was favorable for effective Sb(III) oxidation. Moreover, Sb(V) generated from Sb(III) oxidation by Mn(III/IV) enhanced Mn(II) sorption at the beginning of the process, and thus favored Mn(III/IV) formation, which could further promote Sb(III) oxidation to Sb(V). Overall, this study elucidated the effects of Mn(III/IV) associated with lepidocrocite arisen from Fe(II) oxidation on Sb migration and transformation and revealed the underlying reaction mechanisms, contributing to a better understanding of the geochemical dynamics of Sb.

Availability, Toxicology and Medical Significance of Antimony

Antimony has been known and used since ancient times, but its applications have increased significantly during the last two centuries. Aside from its few medical applications, it also has industrial applications, acting as a flame retardant and a catalyst. Geologically, native antimony is rare, and it is mostly found in sulfide ores. The main ore minerals of antimony are antimonite and jamesonite. The extensive mining and use of antimony have led to its introduction into the biosphere, where it can be hazardous, depending on its bioavailability and absorption. Detailed studies exist both from active and abandoned mining sites, and from urban settings, which document the environmental impact of antimony pollution and its impact on human physiology. Despite its evident and pronounced toxicity, it has also been used in some drugs, initially tartar emetics and subsequently antimonials. The latter are used to treat tropical diseases and their therapeutic potential for leishmaniasis means that they will not be soon phased out, despite the fact the antimonial resistance is beginning to be documented. The mechanisms by which antimony is introduced into human cells and subsequently excreted are still the subject of research; their elucidation will enable us to better understand antimony toxicity and, hopefully, to improve the nature and delivery method of antimonial drugs.

Insight into the Adsorption Behaviors of Antimony onto Soils Using Multidisciplinary Characterization

Antimony (Sb) pollution in soils is an important environmental problem, and it is imperative to investigate the migration and transformation behavior of Sb in soils. The adsorption behaviors and interaction mechanisms of Sb in soils were studied using integrated characterization techniques and the batch equilibrium method. The results indicated that the adsorption kinetics and isotherms of Sb onto soils were well fitted by the first-order kinetic, Langmuir, and Freundlich models, respectively, while the maximum adsorbed amounts of Sb (III) in soil 1 and soil 2 were 1314.46 mg/kg and 1359.25 mg/kg, respectively, and those of Sb (V) in soil 1 and soil 2 were 415.65 mg/kg and 535.97 mg/kg, respectively. In addition, pH ranging from 4 to 10 had little effect on the adsorption behavior of Sb. Moreover, it was found that Sb was mainly present in the residue fractions, indicating that Sb had high geochemical stability in soils. SEM analysis indicated that the distribution positions of Sb were highly coincident with Ca, which was mainly due to the existence of calcium oxides, such as calcium carbonate and calcium hydroxide, that affected Sb adsorption, and further resulted in Sb and Ca bearing co-precipitation. XPS analysis revealed the valence state transformation of Sb (III) and Sb (V), suggesting that Fe/Mn oxides and reactive oxygen species (ROS) served as oxidant or reductant to promote the occurrence of the Sb redox reaction. Sb was mobile and leachable in soils and posed a significant threat to surface soils, organisms, and groundwater. This work provides a fundamental understanding of Sb adsorption onto soils, as well as a theoretical guide for studies on the adsorption and migration behavior of Sb in soils.

Metagenomic analysis reveals the response of microbial community in river sediment to accidental antimony contamination

The mining of deposits containing metals like antimony (Sb) causes serious environmental issues that threaten human health and ecological systems. However, information on the effect of Sb on freshwater sediment microorganisms and the mechanism of microbial Sb resistance is still very limited. This was the first attempt to explore microbial communities in river sediments impacted by accidental Sb spill. Metagenomic analysis revealed the high relative abundance of Proteobacteria and Actinobacteria in all the studied river sediments, showing their advantage in resistance to Sb pollution. Under Sb stress, microbial functions related to DNA repair and ion transport were enhanced. Increase in heavy metal resistance genes (HMRGs), particularly Sb transport-related arsB gene, was observed at Sb spill-impacted sites. HMRGs were significantly correlated with ARGs and MGEs, and the abundant MGEs at Sb spill-impacted sites might contribute to the increase in HMRGs and ARGs via horizontal gene transfer. Deinococcus, Sphingopyxis and Paracoccus were identified as potential tolerant genera under Sb pressure and might be related to the transmission of HMRGs and ARGs. This study can add new insights towards the effect of accidental metal spill on sediment microbial community.

Kinetics of antimony biogeochemical processes under pre-definite anaerobic and aerobic conditions in a paddy soil

While the transformation of antimony (Sb) in paddy soil has been previously investigated, the biogeochemical processes of highly chemical active Sb in the soil remain poorly understood. In addition, there is a lack of quantitative understanding of Sb transformation in soil. Therefore, in this study, the kinetics of exogenous Sb in paddy soils were investigated under anaerobic and aerobic incubation conditions. The dissolved Sb(V) and the Sb(V) extracted by diffusive gradient technique decreased under anaerobic conditions and then increased under aerobic conditions. The redox reaction of Sb occurred, and Sb bioavailability significantly decreased after 55 days of incubation. The kinetics of Fe and the scanning transmission electron microscopy analysis revealed that the Fe oxides were reduced and became dispersed under anaerobic conditions, whereas they were oxidized and re-aggregated during the aerobic stage. In addition, the redox processes of sulfur and nitrogen were detected under both anaerobic and aerobic conditions. Based on these observations, a simplified kinetic model was established to distinguish the relative contributions of the transformation processes. The bioavailability of Sb was controlled by immobilization as a result of S reduction and by mobilization as a result of Fe reductive dissolution and S oxidation, rather than the pH. These processes coupled with the redox reaction of Sb jointly resulted in the complex behavior of Sb transformation under anaerobic and aerobic conditions. The model-based method and findings of this study provide a comprehensive understanding of the Sb transformation in a complex soil biogeochemical system under changing redox conditions.

Relationships between urinary antimony concentrations and depressive symptoms in adults

BACKGROUND

Antimony is widely used in industrial production. The general population may be exposed to long-term low-dose antimony, and there are no studies on antimony and depression symptoms. This study aims to explore the relationships between urinary antimony concentrations and depressive symptoms in adults.

METHODS

We conducted a cross-sectional study using data from U.S. National Health and Nutrition Examination Survey (NHANES) 2007-2016 for urinary antimony (N = 8538). Depressive symptoms were assessed through Patient's Health Questionnaire (PHQ-9). In order to determine the relationships between urinary antimony concentrations and depressive symptoms, binary logistic regression model and restricted cubic spline were used. Dominance analysis was used to explore the relative importance between variables associated with depressive symptoms.

RESULTS

There was a significant positive relationship between urinary antimony concentrations and depressive symptoms in the general population, and OR with 95% CI was 1.72 (1.15, 2.60). This relationship also occurred in participants without disease status, and OR with 95% CI was 2.05 (1.10, 3.82). After stratified gender, the urinary antimony concentrations were positively correlated with depressive symptoms in the highest tertiles of female participants, and OR with 95% CI was 1.74 (1.06, 2.86). After adjusted urinary lead, arsenic, cadmium, and mercury as covariates, the result was still statistically significant, and OR with 95% CI was 1.83 (1.23, 2.72). Restricted cubic spline showed a nonlinear positive relationship between urinary antimony and depressive symptoms. Based on the result of dominance analysis, the relative importance of urinary antimony concentration accounted for 3.58%.

CONCLUSION

This study indicated that urinary antimony was positively related to depressive symptoms, especially in female.

Antimony Immobilization in Primary-Explosives-Contaminated Soils by Fe-Al-Based Amendments

Soils at primary explosives sites have been contaminated by high concentrations of antimony (Sb) and co-occurring heavy metals (Cu and Zn), and are largely overlooked and neglected. In this study, we investigated Sb concentrations and species and studied the effect of combined Fe- and Fe–Al-based sorbent application on the mobility of Sb and co-occurring metals. The content of Sb in soil samples varied from 26.7 to 4255.0 mg/kg. In batch experiments, FeSO₄ showed ideal Sb sorption (up to 97% sorption with 10% FeSO₄·7H₂O), whereas the sorptions of 10% Fe⁰ and 10% goethite were 72% and 41%, respectively. However, Fe-based sorbents enhanced the mobility of co-occurring Cu and Zn to varying levels, especially FeSO₄·7H₂O. Al(OH)₃ was required to prevent Cu and Zn mobilization. In this study, 5% FeSO₄·7H₂O and 4% Al(OH)₃ mixed with soil was the optimal combination to solve this problem, with Sb, Zn, and Cu stabilizations of 94.6%, 74.2%, and 82.2%, respectively. Column tests spiked with 5% FeSO₄·7H₂O, and 4% Al(OH)₃ showed significant Sb (85.85%), Zn (83.9%), and Cu (94.8%) retention. The pH-regulated results indicated that acid conditioning improved Sb retention under alkaline conditions. However, no significant difference was found between the acidification sets and those without pH regulation. The experimental results showed that 5% FeSO₄·7H₂O + 4% Al(OH)₃ without pH regulation was effective for the stabilization of Sb and co-occurring metals in primary explosive soils.

Silicon alleviates antimony phytotoxicity in giant reed (Arundo donax L.)

Silicon enhances photosynthetic efficiency, biomass, and lignification of root structures possibly limiting antimony translocation and mitigating phytotoxicity in giant reed plants. Antimony (Sb) is a non-essential metalloid causing toxic effects in plants. Silicon has been reported to impart tolerance against biotic and abiotic stress in plants. Fast-growing plant, giant reed (Arundo donax L.) is a promising energy crop, can be a suitable plant for phytoremediation. However, information regarding the tolerance capacity with respect to Sb toxicity and potential of Si to mitigate the Sb phytotoxicity in giant reed are very scarce. Rhizomes of giant reed were grown for ten weeks in hydroponics exposed to Sb, Si, and their combination wherein treatment without Sb/Si served as control. Effect of these treatments on rate of net photosynthesis and photosynthetic pigments, phytoextraction ability of Sb, Si and Sb uptake, plant biomass, and lignification and suberization of roots along with localization of Sb and Si were analysed. We found that Si considerably improved the growth and biomass of giant reed under Sb toxicity. Antimony reduced the photosynthesis and decreased the content of photosynthetic pigments, which was completely alleviated by Si. Silicon amendment to Sb treated plants enhanced root lignification. Silicon enhanced lignification of root structures probably restricted the Sb translocation. However, co-localization of Sb with Si has not been observed neither at the shoot nor at the root levels. Similarly, Sb was also not detected in leaf phytoliths. These findings suggest that Si treatment promotes overall plant growth by improving photosynthetic parameters and decreasing Sb translocation from root to shoot in giant reed by improving root lignification.

Evaluation of toxic effects induced by arsenic trioxide or/and antimony on autophagy and apoptosis in testis of adult mice

Arsenic trioxide (ATO) and antimony (Sb) are well-known ubiquitous environmental contaminants and cause unpromising male reproductive effects in target and non-target exposed organisms. The main objective of this study was to investigate the effects of ATO or/and Sb on process of autophagy, apoptosis, and reproductive organ in adult mice. For this reason, a total of 32 adult mice were randomly divided into different groups like control group, ATO-treated group, Sb-treated group, and combined group. The duration of current experimental trial was 2 months. Various adverse effects of ATO or/and Sb on sperm parameters, oxidative stress, autophagy, and apoptosis were determined in testis of mice. Results indicated that parameters of sperm quality for organ coefficient, sperm count, ratio of sperm survival, testosterone level, and germ cells were significantly decreased, while malformation rate and vacuolization significantly increased in mice exposed to different treatments. Furthermore, the status of antioxidant index of T-AOC, SOD, and MsrB1 levels was reduced, while MDA increased significantly in ATO + Sb group. Results on TEM investigation determined that the autophagosomes, autolysosome, nuclear pyknosis, and chromatin condensation were prominent ailments, and the levels of autophagy and pro-apoptosis indictors including Beclin1, Atg-5, LC3B/LC3A, caspase-8, cytc, cleaved caspase-3, p53, and Bax were up-regulated in treated group, while the content of an anti-apoptosis maker (Bcl-2) was down-regulated. In conclusion, the results of our experiment suggested that abnormal process of autophagy and apoptosis was triggered by arsenic and antimony, and intensity of toxic effects increased in combined treatments of ATO and Sb.

Arsenic and antimony co-induced nephrotoxicity via autophagy and pyroptosis through ROS-mediated pathway in vivo and in vitro

Arsenic (As) and antimony (Sb) are commonly accumulated environmental pollutants that often coexist in nature and cause serious widespread biological toxicity. To investigate the nephrotoxicity induced by As and Sb in detail, we explored the mechanism by which As and Sb cotreatment induced autophagy and pyroptosis in vivo and in vitro. In this study, mice were treated with 4 mg/kg arsenic trioxide (ATO) or/and 15 mg/kg antimony trichloride (SbCl₃) by intragastric intubation for 60 days. TCMK-1 cells were treated with ATO (12.5 μM), SbCl₃ (25 μM) or a combination of As and Sb for 24 h. The results of the in vivo experiment demonstrated that As or/and Sb exposure could induce histopathological changes in the kidneys, and increase the levels of biochemical indicators of nephrotoxicity. In addition, As and Sb can co-induce oxidative stress, which further activate autophagy and pyroptosis. In an in vitro experiment, As and/or Sb coexposure increased ROS generation and decreased MMP. Moreover, the results of related molecular experiments further confirmed that As and Sb coactivated autophagy and pyroptosis. In conclusion, our results indicated that As and Sb co-exposure could cause autophagy and pyroptosis via the ROS pathway, and these two metals might have a synergistic effect on nephrotoxicity.

Effects of antimony on anaerobic methane oxidization and microbial community in an antimony-contaminated paddy soil: A microcosm study

Anaerobic methane oxidation (AOM) plays an important role in sinking global methane and thereby in constraining climate change. Anthropogenic activities in antimony (Sb) mines have resulted in Sb contamination in rice fields, which are among the dominant methane sources. However, the knowledge of effects of Sb on AOM in paddy soils and the microbiota involved in this process remains limited. Herein, Sb was amended into the paddy soil to investigate the effects of Sb contamination on AOM and the microbial communities such as methanotrophs. Significant inhibition of AOM was observed in the treatment with Sb addition in comparison with the treatment without Sb addition. The significant increases in the abundance of the mcrA genes, responsible for methane production and oxidation, were observed in the treatment with/without Sb addition. In contrast, no significant increases in the copy number of the mcrA gene were detected in the treatment with the addition of the methanogenic and methanotrophic inhibitor 2-bromoethanesulfonate (BES). These results suggested that Sb contamination might inhibit only AOM but not methane production. In addition, amplicon high-throughput sequencing showed that the Sb addition impaired the diversity of microbial communities and impacted the biotic interactions in the soil. However, the abundance of bacterial methane-oxidizing phylum NC10 and its biotic connections with other microbes were enhanced by the addition of Sb. Pseudogulbenkiania and Methanosarcina dominated the bacterial and archaeal communities in the treatment without Sb addition, while the bacteria Ramlibacter and Geothrix and the archaea Methanomethylovorans were the most abundant genera in the treatment with Sb addition. These analyses of microbial communities indicated that Sb addition had significant effects on both the compositions of bacterial and archaeal communities. This study expands our knowledge of the effects of Sb contamination on AOM and the microbial (especially methanotrophs) diversity and composition in paddy soils.

Mobilisation of hazardous elements from arsenic-rich mine drainage ochres by three Aspergillus species

Natural ferric ochres that precipitate in streambeds at abandoned mining sites are natural scavengers of various metals and metalloids. Thus, their chemical and structural modification via microbial activity should be considered in evaluation of the risks emerging from probable spread of contamination at mining sites. Our results highlight the role of various aspergilli strains in this process via production of acidic metabolites that affect mobility and bioavailability of coprecipitated contaminants. The Mössbauer analysis revealed subtle structural changes of iron in ochres, while the elemental analysis of non-dissolved residues of ochres that were exposed to filamentous fungi suggest coinciding bioextraction of arsenic and antimony with extensive iron mobilisation. However, the zinc bioextraction by filamentous fungi is less likely dependent on iron leaching from ferric ochres. The strain specific bioextraction efficiency and subsequent bioaccumulation of mobilised metals resulted in distinct tolerance responses among the studied soil fungal strains. However, regardless the burden of bioextracted metal(loid)s on its activity, the Aspergillus niger strain has shown remarkable capability to decrease pH of its environment and, thus, bioextract significant and environmentally relevant amounts of potentially toxic elements from the natural ochres.

Antimonate sequestration from aqueous solution using zirconium, iron and zirconium-iron modified biochars

Antimony (Sb) is increasingly being recognized as an important contaminant due to its various industrial applications and mining operations. Environmental remediation approaches for Sb are still lacking, as is the understanding of Sb environmental chemistry. In this study, biosolid biochar (BSBC) was produced and utilized to remove antimonate (Sb(V)) from aqueous solution. Zirconium (Zr), Zirconium-iron (Zr-Fe) and Fe-O coated BSBC were synthesized for enhancing Sb(V) sorption capacities of BSBC. The combined results of specific surface area, FTIR, SEM-EDS, TEM-EDS, and XPS confirmed that Zr and/or Zr-Fe were successfully coated onto BSBC. The effects of reaction time, pH, initial Sb(V) concentration, adsorbate doses, ionic strength, temperature, and the influence of major competitive co-existing anions and cations on the adsorption of Sb(V) were investigated. The maximum sorption capacity of Zr-O, Zr-Fe, Zr-FeCl3, Fe-O, and FeCl3 coated BSBC were 66.67, 98.04, 85.47, 39.68, and 31.54 mg/g respectively under acidic conditions. The XPS results revealed redox transformation of Sb(V) species to Sb(III) occurred under oxic conditions, demonstrating the biochar's ability to behave as an electron shuttle during sorption. The sorption study suggests that Zr-O and Zr-O-Fe coated BSBC could perform as favourable adsorbents for mitigating Sb(V) contaminated waters.

Antimony (V) Adsorption at the Hematite–Water Interface: A Macroscopic and In Situ ATR-FTIR Study

The environmental mobility of antimony (Sb) is largely unexplored in geochemical environments. Iron oxide minerals are considered major sinks for Sb. Among the different oxidation states of Sb, (+) V is found more commonly in a wide redox range. Despite many adsorption studies of Sb (V) with various iron oxide minerals, detailed research on the adsorption mechanism of Sb (V) on hematite using macroscopic, spectroscopic, and surface complexation modeling is rare. Thus, the main objective of our study is to evaluate the surface complexation mechanism of Sb (V) on hematite under a range of solution properties using macroscopic, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic, and surface complexation modeling. The results indicate that the Sb (V) adsorption on hematite was highest at pH 4–6. After pH 6, the adsorption decreased sharply and became negligible above pH 9. The effect of ionic strength was negligible from pH 4 to 6. The spectroscopic results confirmed the presence of inner- and outer-sphere surface complexes at lower pH values, and only outer-sphere-type surface complex at pH 8. Surface complexation models successfully predicted the Sb (V) adsorption envelope. Our research will improve the understanding of Sb (V) mobility in iron-oxide-rich environments.

Evaluating the cytotoxicity of Ge–Sb–Se chalcogenide glass optical fibres on 3T3 mouse fibroblasts

In vivo cancer detection based on the mid-infrared molecular fingerprint of tissue is promising for the fast diagnosis and treatment of suspected cancer patients. Few materials are mid-infrared transmissive, even fewer, which can be converted into functional, low-loss optical fibres for in vivo non-invasive testing. Chalcogenide-based glass optical fibres are, however, one of the few. These glasses are transmissive in the mid-infrared and are currently under development for use in molecular sensing devices. The cytotoxicity of these materials is however unknown. The cytotoxicity of Ge–Sb–Se chalcogenide optical glass fibres on 3T3 mouse fibroblast cells is here investigated. Fibres exposed to four different pre-treatment conditions are used: as-drawn (AD), propylamine-etched (PE), oxidised-and-washed (OW) and oxidised (Ox). To achieve the latter two conditions, fibres are treated with H₂O₂(aqueous (aq.)) and dried to produce a surface oxide layer; this is either washed off (OW) or left on the glass surface (Ox). Cellular response is investigated via 3 day elution and 14 day direct contact trials. The concentration of the metalloids (Ge, Sb and Se) in each leachate was measured via inductively coupled plasma mass spectrometry. Cell viability is assessed using the neutral red assay and scanning electron microscopy. The concentration of Ge, Sb and Se ions after a 3 day dissolution was as follows. In AD leachates, Ge: 0.40 mg L⁻¹, Sb: 0.17 mg L⁻¹, and Se: 0.06 mg L⁻¹. In PE leachates, Ge: 0.22 mg L⁻¹, Sb: 0.15 mg L⁻¹, and Se: 0.02 mg L⁻¹. In Ox leachates, Ge: 823.8 mg L⁻¹, Sb: 2586.6 mg L⁻¹, and Se: 3750 mg L⁻¹. Direct contact trials show confluent cell layers on AD, PE and OW fibres after 14 days, while no cells are observed on the Ox surfaces. A >50% cell viability is observed in AD, PE and OW eluates after 3 days, when compared with Ox eluates (<10% cell viability). Toxicity in Ox is attributed to the notable pH change, from neutral pH 7.49 to acidic pH 2.44, that takes place on dissolution of the surface oxide layer in the growth media. We conclude, as-prepared Ge–Sb–Se glasses are cytocompatible and toxicity arises when an oxide layer is forced to develop on the glass surface.

We present a study that aims to evaluate the cytotoxicity of Ge₂₀Sb10Se₇₀ at% glass optical fibres on 3T3 mouse fibroblast cells. To observe the toxicity of these optical fibres, 3T3 fibroblast proliferation was investigated.

Differential distribution of and similar biochemical responses to different species of arsenic and antimony in Vetiveria zizanioides

Vetiver grass (Vetiveria zizanioides L. Nash) has a great application potential to the phytoremediation of heavy metals pollution. However, few studies explored the bioavailability and distribution of different speciations of As and Sb in V. zizanioides. This study aimed to clarify the allocation and accumulation of two inorganic species arsenic (As(III) and As(V)) and antimony (Sb(III) and Sb(V)) in V. zizanioides, to understand the self-defense mechanisms of V. zizanioides to these metal(loids) elements. Thus, an experiment was conducted under greenhouse conditions to identify distribution of As and Sb in plant roots and shoots. Antioxidant enzymes (superoxide dismutase, SOD) and changes of subcellular structures were tested to evaluate metal(loids) tolerance capacities of V. zizanioides. This study demonstrated that V. zizanioides had higher capacity to accumulate Sb than As. For Sb absorption, Sb(III) content is significantly higher than Sb(V) in tissues of V. zizanioides under all concentration levels, despite the oxidation of Sb(III) on the nutrient solution surface. Additional Sb was mainly accumulated in plant roots due to Sb immobilization by transforming it into precipitates. As was more easily transferred to aerial tissues and had low accumulation rates, probably due to its restricted uptake rather than restricted transport. In many cases, two inorganic species of As and Sb showed almost same biotoxicity to V. zizanioides estimated from its biomass, SOD activity, and MDA content as well as functional groups. In summary, the results of this study provide new insights into understanding allocation, accumulation and phytotoxicity effects of arsenic and antimony in V. zizanioides. Schematic diagram of distribution of and biochemical responses to As(III), As(V), Sb(III), and Sb(V) in tissue of V. zizanioides.

Speciation of antimony in representative sulfidic hot springs in the YST Geothermal Province (China) and its immobilization by spring sediments

As a well-known toxic element, antimony occurred in a wide range of concentrations in the geothermal waters discharging from Rehai and Daggyai, two representative hydrothermal areas in the Yunnan-Sichuan-Tibet Geothermal Province of China. Antimony speciation in different types of the hot springs in Rehai and Daggyai varied greatly as well, and tri- and tetrathioantimonate were detected in most neutral to alkaline Rehai hot springs. Neutral to alkaline pH, high sulfide concentrations, and high sulfide to antimony ratios were the critical factors promoting the formation of thioantimonates. The fact that no thioantimonates were detected in neutral to alkaline Daggyai hot springs is attributed to high concentrations of coexistent arsenic capable of inhibiting the thiolation of oxyantimony anions, because thioantimonates are kinetically more labile than thioarsenates. Upon discharge of the hot springs, both total aqueous antimony and arsenic decreased rapidly and substantially via immobilization to the sediments in the spring vents and their outflow channels. Some of the common iron-bearing minerals in the spring sediments, like pyrite and goethite, are known sinks for antimony and arsenic. Yet, an interesting difference was observed with antimony and iron contents in the sediment samples showing a significant correlation that was lacking for arsenic and iron contents. The explanation might be that for arsenic, sorption affinities are known to vary significantly with aqueous arsenic speciation and mineral phases. Typically, thiolation increases, and oxidation decreases arsenic mobility. Sorption experiments for antimony conducted in the present study, in contrast, showed that different antimony species were comparably sorbed to pyrite over a wide range of initial antimony concentrations and to goethite at relatively low initial antimony concentrations (but still covering the concentration range of antimony in common natural waters), so neither thiolation nor oxidation contributed significantly to the mobility of antimony in the hot springs investigated in this study.

Factors influencing the uptake and speciation transformation of antimony in the soil-plant system, and the redistribution and toxicity of antimony in plants

Antimony (Sb) is not an essential element for humans and plants although it can be used to treat some human diseases, such as schistosomiasis. Sb contamination has been documented in many regions around the world, particularly in China. The Sb contamination in the environment often stems from anthropogenic activities such as mining, smelting, and shooting. Within the latest decade, great progress has been made in research examining the physiochemical behavior of Sb in the environment, including 1) the extent of Sb pollution around the world particularly in China; 2) the mechanisms and factors influencing Sb migration in soils, especially the adsorption/desorption of Sb by minerals or organic materials; 3) the transformations influencing speciation catalyzed by soil microbes; 4) to a lesser extent, the toxicity of Sb to plants and soil animals. In this review, we highlighted the current knowledge with respect to 1) how soil physicochemical properties (including water regimes, pH, organic materials and Eh), and soil organisms will affect the soil bioavailability of Sb, and subsequently the uptake of Sb by plants; 2) the uptake pathway of antimonite and antimonate, the translocation of Sb from roots to shoots, and the redistribution and toxicity of Sb in plants.

Investigation of the Ecological Roles of Putative Keystone Taxa during Tailing Revegetation

Metal contamination released from tailings is a global environmental concern. Although phytoremediation is a promising remediation method, its practice is often impeded by the adverse tailing geochemical conditions, which suppress biological activities. The ecosystem services provided by indigenous microorganisms could alter environmental conditions and facilitate revegetation in tailings. During the process, the keystone taxa of the microbial community are assumed an essential role in regulating the community composition and functions. The identity and the environmental functions of the keystone taxa during tailing revegetation, however, remain unelucidated. The current study compared the microbial community composition and interactions of two contrasting stibnite (Sb₂S₃) tailings, one revegetated and one unvegetated. The microbial interaction networks and keystone taxa were significantly different in the two tailings. Similar keystone taxa were also identified in other revegetated tailings, but not in their corresponding unvegetated tailings. Metagenome-assembled genomes (MAGs) indicated that the keystone taxa in the revegetated tailing may use both organic and inorganic energy sources (e.g., sulfur, arsenic, and antimony). They could also facilitate plant growth since a number of plant-growth-promoting genes, including phosphorus solubilization and siderophore production genes, were encoded. The current study suggests that keystone taxa may play important roles in tailing revegetation by providing nutrients, such as P and Fe, and promoting plant growth.

The antimony sorption and transport mechanisms in removal experiment by Mn-coated biochar

A method of Mn-coated biochar production was developed, which showed great removal ability of trivalent antimony (Sb(III)) (0.94 mg g^-1) and pentavalent antimony (Sb(V)) (0.73 mg g^-1), and the adsorption capacity was stable under different pH. According to the adsorption kinetics and isotherm, the adsorption process of both Sb(III) and Sb(V) was chemisorption, which was both monolayer and poly layers heterogeneous chemisorption process. X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy analyses indicated that the main oxides and functional groups involved in the adsorption were manganese oxides (MnO_x), carboxyl and hydroxyl groups and Sb(V) was combined with Mn-coated biochar by inner-sphere complexation. Sb(III) was oxidized by oxygen and MnO_x which was both on the surface of biochar and dissolved in solution. Furthermore, X-ray absorption near-edge structure (XANES) showed that Sb(V) was the main species after Sb(III) and Sb(V) adsorbed on the Mn-coated biochar. Extended X-ray absorption fine structure (EXAFS) analysis indicated that Sb(III) and MnO_x formed the monodentate mononuclear and corner-sharing complexes with a structure of Mn-O-Sb on Mn-coated biochar. While Sb(V) and MnO_x formed inner-sphere complexes including edge-sharing and corner-sharing complexes. The new synthetic material can contribute to develop new remediation strategies for treating Sb-contaminated water.

Emission control strategies of hazardous trace elements from coal-fired power plants in China

China's energy dependents on coal due to the abundance and low cost of coal. Coal provides a secure and stable energy source in China. Over-dependence on coal results in the emission of Hazardous Trace Elements (HTEs) including selenium (Se), mercury (Hg), lead (Pb), arsenic (As), etc., from Coal-Fired Power Plants (CFPPs), which are the major toxic air pollutants causing widespread concern. For this reason, it is essential to provide a succinct analysis of the main HTEs emission control techniques while concurrently identifying the research prospects framework and specifying future research directions. The study herein reviews various techniques applied in China for the selected HTEs emission control, including the technical, institutional, policy, and regulatory aspects. The specific areas covered in this study include health effects, future coal production and consumption, the current situation of HTEs in Chinese coal, the chemistry of selected HTEs, control techniques, policies, and action plans safeguarding the emission control. The review emphasizes the fact that China must establish and promote efficient and clean ways to utilize coal in order to realize sustainable development. The principal conclusion is that cleaning coal technologies and fuel substitution should be great potential HTEs control technologies in China. Future research should focus on the simultaneous removal of HTEs, PM, SOx, and NOx in the complex flue gas.

Effect of redox variation on the geochemical behavior of Sb in a vegetated Sb(V)-contaminated soil column

This study examined the geochemical behavior of antimony (Sb) in a vegetated contaminated soil column consisting of unsaturated rhizosphere and a waterlogging layer. The results showed a reducing condition (Oxidation-Reduction Potential (ORP) of -171 mV) was formed in about 5 days in the waterlogging zone. The amount of Sb released was higher under the oxidizing unsaturated-rhizosphere compared to that in the waterlogging zone possibly because of the weaker affinity of Sb(V) to Mn- and/or Fe-oxides in soil. The fraction of Sb(III) in the dissolved total Sb increased with time when soil redox states were subjected to a further reduction. Solid phase Sb K-edge X-ray absorption spectroscopy (XAS) of soils showed that Sb(III) fraction of the deeper layer soil increased while the unsaturated upper soil solely composed Sb(V). In this study, 250 mg/kg of Sb pollution did not significantly affect plant growth and no significant transport of Sb occurred from the soil to plant. However, changes in redox conditions within the soil column induced a shift in soil microbial communities. Consequently, the importance of redox states of soil on geochemical behavior of Sb and the effects of soil flooding or waterlogging deserve attention in the management of Sb-contaminated soil.