Sb Contamination Research Articles

Efficient removal of Sb(Ⅴ) from water using sulphidated ferrihydrite via tripuhyite (FeSbO4) precipitation and complexation

Elevated concentrations of antimony (Sb) in the ecological environment have received considerable attention due to the harmful consequence involved. This study synthesized sulphidated ferrihydrite with different S:Fe molar ratios to efficiently remove Sb(V) from water. As the S:Fe molar ratio ranged from 0.00 to 1.48, the removal efficiency of Sb(V) by sulphidated ferrihydrite first decreased before increasing considerably. Sulphidated ferrihydrite with an S:Fe molar ratio of 0.74 exhibited a strong affinity towards Sb(V) with an optimal removal capacity of 963.74 mg Sb/g, which was 3.2−fold higher than that of ferrihydrite. In the kinetic experiments, the removal behavior of Sb(V) was well described by the pseudo−second−order model, suggesting that the removal process was controlled via chemisorption. Moreover, Sb(V) was efficiently removed over a wide pH range of 3.00–11.00, and coexisting anions (NO3−, Cl−, SO42−, SiO32−, CO32− and PO43−) exhibited marginal impact on the Sb(V) removal by sulphidated ferrihydrite (S:Fe ≥ 0.44). The characterization results of XRD, SEM, TEM mapping and etched XPS revealed goethite to be the dominant phase of sulphidated ferrihydrite with an S:Fe molar ratio of 0.15, while a mixed constitution of mixed−valent iron (hydro)oxides and iron sulphide was formed when the S:Fe molar ratio exceeded 0.44. Moreover, sulphidated ferrihydrite acted as a donor for Fe and S for the effective retention of Sb(V) by two main pathways: precipitation (tripuhyite, FeSbO4) and complexation (≡S–H and ≡Fe–OH). Therefore, sulphidated ferrihydrite is a promising material for eliminating Sb(V) contamination from water.

Different responses of bacteria and fungi to environmental variables and corresponding community assembly in Sb-contaminated soil

Bacterial communities in antimony (Sb) polluted soils have been well addressed, whereas the important players fungal communities are far less studied to date. Here, we report different responses of bacterial and fungal communities to Sb contamination and the ecological processes controlling their community assembly. Soil samples in the Xikuangshan mining area were collected and subjected to high through-put sequencing of 16S rRNA and ITS1 to investigate bacterial and fungal communities, respectively, along an Sb gradient. Sb speciation in the soil samples and other physicochemical parameters were analyzed as well. Bacterial communities were dominated by Deltaproteobacteria in the soil with highest Sb concentration, whereas Chloroflexi were dominant in the soil with lowest Sb concentration. Fungal communities in high-Sb soils were predominated by unclassified Fungi, whilst Leotiomycetes were dominant in low-Sb soil samples. Multivariate analysis indicated that Sb, pH and soil texture were the main drivers to strongly impact microbial communities. We further identified Sb-resistant microbial groups via correlation analysis. In total, 18 bacterial amplicon sequence variants (ASVs) were found to potentially involve in biogeochemical cycles such as Sb oxidation, sulfur oxidation or nitrate reduction, whereas 12 fungal ASVs were singled out for potential heavy metal resistance and plant growth promotion. Community assembly analysis revealed that variable selection contributed 100% to bacterial community assembly under acidic or high Sb concentration conditions, whereas homogeneous selection dominated fungal community assembly with a contribution over 78.9%. The community assembly of Sb-resistant microorganisms was mainly controlled by stochastic process. The results offer new insights into microbial ecology in Sb-contaminated soils, especially on the different responses of microbial communities under identical environmental stress and the different ecological processes underlining bacterial and fungal community assembly.

Source, degree and potential health risk of metal(loid)s contamination on the water and soil in the Söke Basin, Western Anatolia, Turkey.

Water and soil quality are the two most important parameters for sustainable agriculture and regional development in the basin. This study focused on the causes of soil and water contamination and the potential impact of drinking water on community health. Reasons for metal(loid)s enrichment in the water and soil in the Söke Basin were examined by considering anthropogenic and geogenic inputs. Four rock samples in the drainage network, 28 soil samples, and 29 water samples in the Söke Plain were collected. All samples were analyzed for metal(loid)s by inductively coupled plasma-mass spectrometry (ICP-MS). The carcinogenic and non-carcinogenic effects of water on human health were calculated mathematically. Potential ecological risk index (PERI), enrichment factor (EF), and ecological risk (ER) were calculated for the soil samples. In addition, principal component analysis (PCA) with Varimax rotation and Kaiser normalization was applied to the soil data set. Cr, Ni, and Cd contamination in soils was associated with anthropogenic inputs, while arsenic contamination was related to both anthropogenic and geogenic inputs. As, B, Ba, Pb, and Sb contamination was found in some drinking water. As contamination has been clearly found to be caused by natural geological processes in and around Lake Azap. It was determined that metal(loid)s enrichment occurred in drinking water due to the mixing of geothermal waters affected by seawater intrusion with surface and groundwater. Contamination inputs were geogenic, but their negative impacts appearing in surface water and drinking water occurred due to human influence.

Recycling the steel pickling waste liquor to produce a low-cost material for immobilization of heavy metal(loid)s

This work aims to demonstrate the practicability of employing Iron (Fe)-manganese (Mn) binary oxide (FMBO) synthesized from pickling wastewater to immobilize arsenic (As(V)) and antimony (Sb(V)). Visual MINTEQ software was used to simulate the speciation of As(V) and Sb(V) under different pH values. The adsorption performance of FMBO for Sb(V) and As(V) were examined by batch experiments, the pH impact, sorption kinetics, sorption isotherms and the reuse of the adsorbent were investigated. The pH impact results demonstrated that the absorption capacity decreased dramatically as the pH value increased, the maximum adsorption capacities As(V) and Sb(V) were obtained at pH value of 4 as 95.24 and 147.1 mg/g, respectively. The kinetic results indicated that the pseudo-second order model could fit the kinetic data of Sb(V) and As(V) well. Equilibrium studies displayed that the adsorption of Sb(V) and As(V) on FMBO could be appropriately described by Freundlich model. Results of the binary adsorption indicated that Sb(V) exhibited ∼ 5% improvement for As(V) when the initial Sb(V) content raised from 0 to 500 mg/L, while As(V) showed a significant hindrance for Sb(V) adsorption. Moreover, utilization of FMBO could also effectively reduce the TCLP extractable and easy mobile As and Sb in contaminated soil, thus reducing their bioavailability. In view of the advantages of cost-effective, eco-friendly and excellent sorption performance, the steel pickling waste liquor-derived FMBO could be regarded as a promising amendment for remediating As and Sb contamination in environment. • A new low-cost adsorbent (FMBO) was prepared from steel pickling waste liquor. • FMBO exhibited an excellent performance for sorption of As(V) and Sb(V). • The existence of Sb(V) favor As(V) sorption, while As(V) showed opposite effect on Sb(V). • The FMBO could also effectively reduce the bioavailability of soil As and Sb.

Geochemical Baseline and Contamination Level Assessment of Antimony (Sb) in Sediment around Agbaou Gold Mine, Côte d’Ivoire

Agbaou is one of the most recent gold mine exploitation sites in Côte d’Ivoire. Little studies are discussed on the geochemical baseline concentration of trace metals in the wetland sediments around Agbaou gold mine. The main objectives of this study were to establish geochemical baseline values and to assess the pollution status of antimony (Sb). The geochemical baseline concentration of Sb (GBCSb) was estimated using linear regression method. In this study, total Sb concentration was analysed in sediment (10 sediment samples) collected around Agbaou gold mine site. The average Sb concentration was 5.63 ± 2.50 µg.g-1 ranging from 2.50 to 11.3 µg.g-1. The spatial distribution of Sb showed a tendency to accumulate near gold mine site. Moreover, the GBCSb (5.72 µg.g-1) was slightly higher than the average concentration found in sediments. GBC of Sb was used to calculate the anthropogenic contribution rate (R) which exhibited a positive value (R > 0) for all samples, indicating that the sediments were influenced by gold mining activities. Due to lack of local baseline value in the study area, the GBCSb obtained could be used as reference value for Sb contamination level assessment in the sediments.

Synergistic Impacts of Arsenic and Antimony Co-contamination on Diazotrophic Communities.

Nitrogen (N) shortage poses a great challenge to the implementation of in situ bioremediation practices in mining-contaminated sites. Diazotrophs can fix atmospheric N2 into a bioavailable form to plants and microorganisms inhabiting adverse habitats. Increasing numbers of studies mainly focused on the diazotrophic communities in the agroecosystems, while those communities in mining areas are still not well understood. This study compared the variations of diazotrophic communities in composition and interactions in the mining areas with different extents of arsenic (As) and antimony (Sb) contamination. As and Sb co-contamination increased alpha diversities and the abundance of nifH encoding the dinitrogenase reductase, while inhibited the diazotrophic interactions and substantially changed the composition of communities. Based on the multiple lines of evidence (e.g., the enrichment analysis of diazotrophs, microbe-microbe network, and random forest regression), six diazotrophs (e.g., Sinorhizobium, Dechloromonas, Trichormus, Herbaspirillum, Desmonostoc, and Klebsiella) were identified as keystone taxa. Environment-microbe network and random forest prediction demonstrated that these keystone taxa were highly correlated with the As and Sb contamination fractions. All these results imply that the above-mentioned diazotrophs may be resistant to metal(loid)s.

Exploring distribution of potentially toxic elements in soil profiles to assess the geochemical background and contamination extent in soils of a metallurgical and industrial area in Kosovo

This geochemical study explored the distribution of potentially toxic elements (PTEs), such as As, Cd, Co, Cr, Cu, Ni, Pb, Sb, Tl, U, and Zn, along soil profiles of a metallurgical and industrial area in Kosovo, with the aim of assessing geochemical background and contamination threshold of PTEs in soil, and defining surface and vertical level and extent of soil contamination by PTEs. The geochemical background was assessed by exploratory data analysis of PTE concentrations in soil profiles. The upper limit of geochemical background (contamination threshold) was used as reference value to calculate the single pollution index and establish the PTE contamination level. Cadmium, Pb, Sb, Zn were the primary soil contaminants and As, Cu, Tl the secondary ones. The main sources of soil contaminants were the Zvecan smelter for Pb, Sb, As, Cu, Tl, and the Trepca industrial complex for Cd and Zn. The highest levels of Pb and Sb contamination were found up to depths between 30 and 60 cm in soil profiles within 5 km north and south-east of the Zvecan smelter. Contamination by Pb and Sb decreased with depth and affected the whole thickness of soil profiles closer the smelter. Cadmium and Zn contamination declined with distance from the Trepca industrial complex and decreased with depth, extending down to depths of 40–90 cm and 30–70 cm, respectively. Anomalous natural concentrations of Co, Cr, and Ni were found in soils collected in the northern part of the study area, where the geology consists mainly of ultrabasic and basic magmatic rocks.

Effects of antimony (III/V) on microbial activities and bacterial community structure in soil

Antimony (Sb) primarily exists in trivalent (III) and pentavalent (V) speciation in the soil environment and poses a potential threat to ecological soil function as a toxic metalloid element. To evaluate the ecological effect of Sb in soil, the effects of different concentrations of Sb(III) and Sb(V) on microbial biomass carbon (MBC), soil basal respiration (SBR), potential nitrification rate (PNR), five enzyme activities and bacterial community structure were investigated using biochemical methods and high-throughput sequencing technology during the 1st and 8th weeks of exposure. The results of these experiments indicated that MBC and SBR were influenced, and PNR, FDA hydrolysis activity and urease activity were significantly inhibited by Sb(III) and Sb(V), while the activities of dehydrogenase, acid phosphatase and β-glucosidase had no clear effects on the amounts of Sb(III) or Sb(V). Meanwhile, there are some discrepancies regarding the effects of Sb(III) and Sb(V) on the same microbial indicators, and incubation time is not a neglected factor. Sequencing analysis revealed that Sb(III) decreased the bacterial diversity indexes and abundances of specific bacteria at the phylum level, whereas Sb(V) had little effect on them. The bacterial community structure at the genus level was altered by Sb(III) and Sb(V), in which the abundances of some functional microbes were increased, while the abundances of some functional microbes were reduced under Sb pollution. In general, PNR, FDA hydrolysis activity, urease activity and the abundances of specific functional microbes (i.e., Nitrospira) could be considered as sensitive indicators of Sb contamination. This study highlights the ecological effect of Sb(III) and Sb(V) on agricultural soil and will provides references for environmental monitoring and assessment.

Effects of different antimony contamination levels on paddy soil bacterial diversity and community structure

To clarify the response mechanism of paddy soil microorganisms to contamination caused by antimony (Sb) alone, we added K(SbO)C4H4O6.1/2 H2O with different contents to uncontaminated paddy soil and carried out related studies. 16S rRNA was sequenced in V3-V4 regions of paddy soil bacteria with different Sb contamination levels. Then, α diversity and species enrichment and separation of paddy soil microorganisms were analyzed. The biochemical behavior and the influences of Sb fractions on bacterial communities and ecological function were explored in paddy soil with different contamination levels. The results showed that the contents of Sbtot and Sb(V) increased with the increase of contamination level, and the difference was significant among the groups. For Sbexe and Sbsrp there were slight differences between S100 and S200 groups, but significant differences among other groups. The diversity index increased with the increase of Sb concentration, which reached the maximum value in S200 group and the minimum value in control group (SC). The relative importance analysis demonstrated that Sb(III) and Sbsrp were the main Sb fractions affecting the diversity index of bacterial community. In addition, the results of principal coordinate analysis (PCoA) showed that there were significant differences between the bacterial communities in SC and in the soil with different Sb contamination levels. Based on diversity analysis, it was found that Proteobacteria, Actinobacteria and Bacteroidetes were the main dominant phyla in paddy soil with different Sb concentrations, and their enrichment and separation were greater than those of other dominant phyla. Though the Static Bayesian network inference, it was shown that Sbtot affected Sphingomonadaceae, and Sbsrp affected Burkholderiaceae, Xanthomonadaceae and Acidobacteriale to further affect bacterial communities, while Sb(V) mainly affected Flavobacteriaceae, Rhodopirillaceae and Acidobacteriale. The above results provide a scientific basis for the biochemical restoration potential of paddy soils with different Sb contamination levels.

Effects of antimony contamination on bioaccumulation and gut bacterial community of earthworm Eisenia fetida

Antimony (Sb) contamination has brought great environmental problems to the surrounding soils. However, few studies focused on the response of bacterial communities in earthworm gut to Sb. Eisenia fetida was cultured in four soils with Sb contents (5,25,50,100 mg•kg−1) to investigate the distribution of Sb species in earthworm gut and the response mechanism of bacterial communities to Sb contamination. The results showed that Sb accumulated in the gut and tissues of earthworms, and the mortality of earthworms showed a dose-response relationship with the increase of Sb content. Sb(III) and Sbexe were the major species in gut, whereas Sb(V) and Sbsrp were predominant in surrounding soil. There were significant differences in bacterial diversity between earthworm gut and soil, but there was no significant between the two with different Sb content. The network constructed by gut bacterial community of earthworm was less stable and more sensitive to Sb species than that in soil. Sb(III) had the greatest influence on the gut bacterial community of earthworm, which not only directly affected the community through Xanthomonadaceae, Rhodomicrobiaceae and Anaerolineaceae, but also indirectly influenced through Chthoniobacteraceae. This study fills a research gap on the effect of Sb contamination on the gut bacterial community of earthworm.

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.

Interaction of aqueous antimony(III) with synthetic ferrous sulfide

Ferrous sulfide (FeS) is an important carrier for metal(loid)s in anoxic environments, but the effect of FeS on the behavior of Sb is poorly understood. This work investigated the interaction of Sb(III) with FeS under anoxic condition. FeS was synthesized and both equilibrium and kinetic experiments on the interaction of Sb(III) with synthesized FeS were conducted at various pH values. The final solid phases were examined by SEM, XRD, TEM, and XPS. The results showed that the uptake of Sb(III) by FeS increased as pH decreased. The kinetic experiment at pH 5 obviously showed that the temporal decrease of Sb(III)aq coincide with the partial dissolution of FeS. In contrast, both the concentrations of Sb(III)aq and FeS in the kinetic experiment at pH 9 did not vary with time. The examination of the solid phases revealed the formation of amorphous Sb2S3 in the experiments at pH 5 and 7.5. Different mechanisms were suggested to affect the interaction of Sb(III) with FeS under acidic and alkaline conditions. At pH 9, adsorption dominated in the interaction. The decrease of Sb(III)aq and the concomitant partial dissolution of FeS at pH 5 indicated the replacement of FeS by Sb2S3, which was more significant at lower pH. The replacement of FeS by Sb2S3 was a relatively slow process compared to the acidic dissolution of FeS. The result of this study helps understand the mobility of Sb in anoxic environments and may favor the remediation of Sb contamination by the use of FeS.

Bacteria responsible for antimonite oxidation in antimony-contaminated soil revealed by DNA-SIP coupled to metagenomics.

Antimony (Sb), the analog of arsenic (As), is a toxic metalloid that poses risks to the environment and human health. Antimonite (Sb(III)) oxidation can decrease Sb toxicity, which contributes to the bioremediation of Sb contamination. Bacteria can oxidize Sb(III), but the current knowledge regarding Sb(III)-oxidizing bacteria (SbOB) is limited to pure culture studies, thus underestimating the diversity of SbOB. In this study, Sb(III)-oxidizing microcosms were set up using Sb-contaminated rice paddies as inocula. Sb(III) oxidation driven by microorganisms was observed in the microcosms. The increasing copies and transcription of the arsenate-oxidizing gene, aioA, in the microcosms during biotic Sb(III) oxidation indicated that microorganisms mediated Sb(III) oxidation via the aioA genes. Furthermore, a novel combination of DNA-SIP and shotgun metagenomic was applied to identify the SbOB and predict their metabolic potential. Several putative SbOB were identified, including Paracoccus, Rhizobium, Achromobacter and Hydrogenophaga. Furthermore, the metagenomic analysis indicated that all of these putative SbOB contained aioA genes, confirming their roles in Sb(III) oxidation. These results suggested the concept of proof of combining DNA-SIP and shotgun metagenomics directly. In addition, the identification of the novel putative SbOB expands the current knowledge regarding the diversity of SbOB.

Bacteria responsible for nitrate-dependent antimonite oxidation in antimony-contaminated paddy soil revealed by the combination of DNA-SIP and metagenomics

Antimonite (Sb(III)) oxidation (SbO) can decrease the toxicity of antimony (Sb) and its uptake into rice, thus serving an ecological role in bioremediation of Sb contamination in rice paddies and decreasing the translocation and accumulation of Sb in rice. Nitrate as the electron acceptor can be coupled to SbO in anoxic environments, which, however, has not been reported in paddy soils. Here we investigate the potential for nitrate-dependent SbO in Sb-contaminated rice paddies and identify nitrate-dependent Sb(III)-oxidizing bacteria (SbOB) using stable isotope probing (SIP) coupled with amplicon and shotgun metagenomic sequencing. Anaerobic SbO was exclusively observed in the paddy soil amended with both Sb(III) and NO3−, whereas no apparent SbO was detected in the soil amended with Sb(III) only. The increasing abundance of the arsenite oxidase gene (aioA) suggests that nitrate-dependent SbO was catalysed by microorganisms harbouring the aioA gene. After 60-day DNA-SIP incubation, an obvious shift in the relative abundance of aioA gene to heavy DNA fractions occurred only in the treatment amended with 13C–NaHCO3, Sb(III) and NO3−, suggesting the incorporation of 13C by nitrate-dependent SbOB. Accordingly, a number of putative nitrate-dependent SbOB were identified in the paddy soil, including Azoarcus, Azospira and Chelativorans. Metagenomic analysis further revealed that they contained aioA genes and genes involved in denitrification and carbon fixation, supporting their capability for nitrate-dependent SbO. These observations suggested the occurrence of nitrate-dependent SbO in paddy soils. A number of putative nitrate-dependent SbOB (i.e., Azoarcus, Azospira and Chelativorans) were reported here, which expands our current knowledge regarding the diversity of nitrate-dependent SbOB. In addition, this study provides a proof of concept using DNA-SIP to identify nitrate-dependent SbOB.

New insight in adsorption of Sb(III)/Sb(V) from waters using magnetic nanoferrites: X-ray absorption spectroscopy investigation

Antimony (Sb) is widely used in many agricultural and industrial application. However, Sb contamination can threaten ecosystem and human health. This study attempts to find a simple and fast way in removing Sb, especially for severely toxic Sb(III) from waters. Six kinds of magnetic nanoferrites (CuFe2O4, MnFe2O4, CoFe2O4, NiFe2O4, ZnFe2O4, Fe3O4) were synthesized to investigate their ability in removing Sb(III) and Sb(V) from aquatic systems. Sb K-edge XANES spectra indicated that Sb(V) was adsorbed on the surface of ZnFe2O4 and would not be converted to more toxic Sb(III). Contrarily, Sb(III) was observed to be adsorbed on ZnFe2O4 and ZnFe2O4 could oxidize Sb(III) to Sb(V). O K-edge XANES analyses showed the downswing of Fe 3d-O 2p characteristic peak after adsorption, which proved again that ZnFe2O4 had the great potential to adsorb and oxidize Sb(III) in aqueous solutions. EXAFS revealed that the peaks on k-space and R-space were quite different, implying that Sb(III) and/or Sb(V) did not replace Fe and/or Zn during the adsorption process. Additionally, XRD spectrum showed that after adsorption of Sb(III) and/or Sb(V), the structure of ZnFe2O4/Fe3O4 remained as fcc spinel structure (Fd-3m), indicating that these nanoferrites possessed good structural stability. This study provided essential information for designing a rapid and effective Sb removal technique in treating Sb-contaminated river water, tap water, and groundwater.

Distribution and speciation of Sb and toxic metal(loid)s near an antimony refinery and their effects on indigenous microorganisms

Although several studies have investigated the effects of Sb contamination on surrounding environments and indigenous microorganisms, little is known about the effect of co-contamination of Sb and toxic metal(loid)s. In this study, the occurrence of Sb and other toxic metal(loid)s near an operating Sb refinery and near-field landfill site were investigated. Topsoil samples near the refinery had high Sb levels (∼3250 mg kg−1) but relatively low concentrations of other toxic metal(loid)s. However, several soil samples taken at greater depth from the near-field landfill site contained high concentrations of As and Pb, as well as extremely high Sb contents (∼21,400 mg kg−1). X-ray absorption fine structure analysis showed that Sb in the soils from both sites was present as Sb(V) in the form of tripuhyite (FeSbO4), a stable mineral. Three-dimensional principal coordinate analysis showed that microbial community compositions in samples with high toxic metal(loid)s concentrations were significantly different from other samples and had lower microbial populations (∼104 MPN g−1). Sequential extraction results revealed that Sb is present primarily in the stable residual fraction (∼99 %), suggesting low Sb bioavailability. However, microbial redundancy analysis suggested that the more easily extractable Pb might be the major factor controlling microbial community compositions at the site.

Comparative characterization of microbial communities that inhabit arsenic-rich and antimony-rich contaminated sites: Responses to two different contamination conditions

Due to extensive mining and industrial activities, arsenic (As) and antimony (Sb) contaminations are becoming a global environmental concern. Both As and Sb are toxic and carcinogenic metalloids from the group 15 in the periodic table. Since As and Sb share many similar geochemical properties, it is often assumed that they exert similar environmental pressure on the native microbial communities. This hypothesis, however, still requires further confirmation. In the current study, a systematic comparison of microbial responses to As and Sb contamination were conducted. The results suggested that regular geochemical parameters, such as pH, nitrate, and TOC, were the driving forces for shaping the microbial community. In correspondence, two heavily contaminated groups showed similar microbial community compositions and the same microbial populations were enriched. The interactions between the contaminant fractions (As and Sb related fractions) and the individual OTUs, however, suggested the different and more diverse impacts of As comparing to Sb fractions, with more taxa significantly impacted by As species comparing to Sb species. The identification of the keystone taxa in the heavily contaminated samples revealed a group of microbial populations that could survive in both As and Sb heavily contaminated conditions and may providing critical environmental services to the community. Further investigation of these key microbial populations may provide valuable insights on employing these microorganisms for remediation applications.

Synthesis of Fe3O4 magnetic nanoparticles coated with cationic surfactants and their applications in Sb(V) removal from water

Antimony (Sb) pollution was an emerging environmental risk in several contaminated waters, whereas its removal still presented as a severe challenge due to the lack of efficient adsorbent and its further removal mechanism. In this study, synthesized absorbents, Fe3O4 magnetic nanoparticles (Fe-MNPs) modified and dispersed with commonly used cationic surfactants, were applied to remove Sb contamination in real surface waters, its synthesized conditions, removal performance and mechanism were investigated by using batch experiments and characterization analyses. Optimum conditions on Sb(V) (the dominant form is Sb(OH)6−) removal by modified adsorbents were obtained as: cetylpyridinium chloride (CPC) coated on Fe-MNPs, mass ratio of Fe-MNPs: CPC = 4:1 and pH = 3–5. Magnetic properties of synthesized adsorbent were not affected, dispersibility was enhanced after fabrication of CPC, that indicated the Fe-MNPs@CPC could be separated and reused with external magnetic field. The adsorption efficiency of this low-cost adsorbent coated with CPC was superior than several traditional adsorbents. The practical application of Fe-MNPs@CPC in five types real waters from the Xikuangshan (XKS) Sb mine area and regeneration experiments by 1 M (mol/L) NaOH solution further confirm its practicability and reusability. Removal experiment results, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) spectra suggested that electrostatic attraction and surface bonding might responsible for the Sb(V) removal by Fe-MNPs modified with cationic surfactants.

Characteristics of Bacterial Community and Function in Paddy Soil Profile around Antimony Mine and Its Response to Antimony and Arsenic Contamination.

Research of bacterial communities and metabolism potential of paddy soils contaminated by antimony (Sb) and arsenic (As) are vital to acquire understanding for their bioremediation. Here, the relative abundance of Sb and As metabolism genes, the diversity and composition of the bacterial community, and the influences of geochemical properties and the bacterial community and metabolism potential have been researched by Tax4Fun2 prediction and high-throughput sequencing. LEfSe (linear discriminant analysis effect size) analysis shown different taxa were enriched in dissimilar soil layers. RDA (Redundancy analysis) and relative importance analysis indicated the main properties including total sulfur (TS), total organic carbon (TOC), pH, and the bioavailable fractions of Sb and As affects the bacterial community, which Sbrec, Astot, and Asrec had greater impact on the bacterial taxonomic community. For example, Asrec, Astot, and Sbrec had a positive correlation with Chloroflexi and Rokubacteria, but negatively correlated with Proteobacteria and Actinobacteria. Obtaining metabolic function genes by using the tax prediction method. RDA, relative importance analysis, and co-occurrence network analysis showed the geochemical properties and bacterial community affected Sb and As related bacterial functions. The partial least squares path model (PLS-PM) analysis indicated Sb and As contamination fractions had negative effects on ecological function, bacterial community structure had positive influences on ecological function, and the direct effects of geochemical properties on ecological function was greater than community structure. The direct impact of As contamination fractions on bacterial community structure was greater than Sb, while the direct impact of Sb contamination fractions on bacterial function was more remarkable than As. Obviously, this study provides a scientific basis for the potential of biochemical remediation of Sb and As contamination in paddy soils profile.

Environmental interaction of antimony and arsenic near busy traffic nodes

Antimony (Sb) and arsenic (As) are elements with similar chemistry, toxicity and binding properties, but different environmental risks and prevailing anthropogenic sources. A significant source of Sb contamination is associated with braking in extremely loaded traffic areas, where the produced abrasion dust contains up to 5% wt. of Sb2S3. In these same exposure areas, As still originates mostly from the combustion of fossil fuels. Heavily loaded crossroads from three different regions of the Czech Republic (Central Europe) were monitored for Sb content in road dusts, topsoils and reference soils during a two-year season (2016–2017). The same samples were also tested for As content to evaluate current contamination trends of both elements in exposed urban areas. The concentration of Sb varied from 5 to 70 µg g−1 in topsoils, and from 20 to 350 µg g−1 in road dusts with the preference for binding to the fine particle fraction (<0.1 mm). The average Sb concentration was up to 60 times the background value and decreased in the order: brake abrasion (103 µg g−1) > road dust (102 µg g−1)> topsoils (101 µg g−1) >> reference soils (<1 µg g−1). The concentration of As in road dust, topsoils and reference soils had about the same level, 101 µg g−1 indicating a more regional character of As pollution. Correlation factors for Sb/As versus iron (Fe)/organic matter (OM) indicated a more robust correlations in soils compared to road dusts and generally better correlations of Sb compared to As. While arsenic contamination has recently decreased thanks to a massive decline of arsenic emissions, antimony contamination indicates a dangerous trend due to growing automotive traffic.