Antimony speciation in soil samples along two Austrian motorways by HPLC-ID-ICP-MS

Transcriptomic and metabolomic insights into the antimony stress response of tall fescue (Festuca arundinacea)

Antimony (Sb) is a toxic heavy metal that severely inhibits plant growth and development and threatens human health. Tall fescue, one of the most widely used grasses, has been reported to tolerate heavy metal stress. However, the adaptive mechanisms of Sb stress in tall fescue remain largely unknown. In this study, transcriptomic and metabolomic techniques were applied to elucidate the molecular mechanism of the Sb stress response in tall fescue. These results showed that the defense process in tall fescue was rapidly triggered during the early stages of Sb stress. Sb stress had toxic effects on tall fescue, and the cell wall and voltage-gated channels are crucial for regulating Sb permeation into the cells. In addition, the pathway of glycine, serine and threonine metabolism may play key roles in the Sb stress response of tall fescue. Genes such as ALDH7A1 and AGXT2 and metabolites such as aspartic acid, pyruvic acid, and biuret, which are related to biological processes and pathways, were key genes and compounds in the Sb stress response of tall fescue. Therefore, the regulatory mechanisms of specific genes and pathways should be investigated further to improve Sb stress tolerance.

Fate of antimony contamination generated by road traffic - A focus on Sb geochemistry and speciation in stormwater ponds

Although antimony (Sb) contamination has been documented in urban areas, knowledge gaps remain concerning the contributions of the different sources to the Sb urban biogeochemical cycle, including non-exhaust road traffic emissions, urban materials leaching/erosion and waste incineration. Additionally, details are lacking about Sb chemical forms involved in urban soils, sediments and water bodies. Here, with the aim to document the fate of metallic contaminants emitted through non-exhaust traffic emissions in urban aquatic systems, we studied trace element contamination, with a particular focus on Sb geochemistry, in three highway stormwater pond systems, standing as models of surface environments receiving road-water runoff. In all systems, differentiated on the basis of lead isotopic signatures, Sb shows the higher enrichment factor with respect to the geochemical background, up to 130, compared to other traffic-related inorganic contaminants (Co, Cr, Ni, Cu, Zn, Cd, Pb). Measurements of Sb isotopic composition (δ¹²³Sb) performed on solid samples, including air-exposed dusts and underwater sediments, show an average signature of 0.07 ± 0.05‰ (n = 25, all sites), close to the δ¹²³Sb value measured previously in certified reference material of road dust (BCR 723, δ¹²³Sb = 0.03 ± 0.05‰). Moreover, a fractionation of Sb isotopes is observed between solid and dissolved phases in one sample, which might result from Sb (bio)reduction and/or adsorption processes. SEM-EDXS investigations show the presence of discrete submicrometric particles concentrating Sb in all the systems, interpreted as friction residues of Sb-containing brake pads. Sb solid speciation determined by linear combination fitting of X-Ray Absorption Near Edge Structure (XANES) spectra at the Sb K-edge shows an important spatial variability in the ponds, with Sb chemical forms likely driven by local redox conditions: "dry" samples exposed to air exhibited contributions from Sb(V)-O (52% to 100%) and Sb(III)-O (<10% to 48%) species whereas only underwater samples, representative of suboxic/anoxic conditions, showed an additional contribution from Sb(III)-S (41% to 80%) species. Altogether, these results confirm the traffic emission as a specific source of Sb emission in surface environments. The spatial variations of Sb speciation observed along the road-to-pond continuum likely reflect a high geochemical reactivity, which could have important implications on Sb transfer properties in (sub)surface hydrosystems.

Valency distributions and geochemical fractions of arsenic and antimony in non-ferrous smelting soils with varying particle sizes

Arsenic and antimony are common toxic metalloids found in associated minerals. These metalloids generally cause high-concentration pollution in non-ferrous metal smelting soils; however, few studies have investigated the pollution characteristics of these two metalloids at non-ferrous smelting sites using varying soil particle sizes. In this study, the valency distributions and geochemical fractions were investigated with varying soil particle sizes (≤ 0.05, 0.05-0.25, 0.25-1, and 1-2 mm). Soils were mainly concentrated in ≤ 0.05 and 0.05-0.25 mm with mass percentages of 32.97% and 29.02%, respectively. The highest total As and Sb concentrations in ≤ 0.05 mm were found to be 20,350 and 3655 mg/kg, respectively. In addition, As(Ⅲ), As(Ⅴ), Sb(Ⅲ), and Sb(Ⅴ) concentrations in this soil particle size were found to be 224, 19,813, 1036, and 24 mg/kg, respectively. The geochemical fractions of As and Sb in varying soil particle sizes were mainly residual, accounting for 50% and 90% in the ≤ 0.05 mm. Soil may bind ≤ 0.25 mm due to the disparity found in the geochemical compositions and valency distributions of arsenic and antimony. X-ray diffraction and scanning electron microscopy/energy dispersive system analysis confirmed that arsenolite accumulated in particle sizes of ≤ 0.05 and 0.05-0.25 mm. The results of this study may provide a scientific reference for risk assessment and restoration strategies for non-ferrous metal smelting soils.

Review of the interactions between vehicular emitted potentially toxic elements, roadside soils, and associated biota

Given the large size of the world road network, the land area affected by vehicular emissions is extensive. This review provides the first global picture of the relationships between vehicular emitted potentially toxic elements, roadside soils, and risks to associated biota. The following potentially toxic elements that accumulate in roadside soils have been examined in this review: As, Co, Cr, Cu, Mn, Mo, Ni, Pb, Pd, Pt, Rh, Se, Sb, Sn, Sr, Ti and Zn. The meta-analysis undertaken demonstrated an increase in concentrations of Cd, Pb, Zn, Pt, Pd and Rh in roadside soils compared to the mean global crustal concentrations. Positive correlations between potentially toxic element concentrations in roadside soil, plants, microbes, and animals were observed. Roadside studies have found increased potentially toxic element concentrations in plants and animals with increasing proximity to roads. The mean concentrations of Pb in roadside plants and vertebrates were at values above the World Health Organisation guidelines. Research has shown a range of impacts of potentially toxic elements in roadside soils on microbial activity including decreased litter decomposition, nitrogen fixation, nutrient cycling and enzyme synthesis. However, aside from the impact on microbial communities, there has been little research investigating the impacts of roadside soil elements on the associated biota. Thus, there is a need for research that investigates the toxicity of elements in roadside soils to plants and animals and to investigate the transfer of roadside elements through the food chain, and thus, risks posed to human health and the environment.

Bioaccessibility of antimony and other trace elements from lead shot pellets in a simulated avian gizzard environment

Many studies have used grit (in the form of lead (Pb) pellets) presence in avian gizzards as an indicator of Pb shot exposure. However, due to nearly complete pellet absorption in gizzards or rapid passage of pellets, the absence of Pb shot presence in a gizzard does not confirm lack of Pb shot exposure. This study provides the basis for an additional technique to identify if elevated tissue Pb concentration is due to Pb shot exposure. Bioaccessibility of Pb and trace elements (Sb, As, and Sn) present in Pb shot were quantified to determine if any of these elements would be useful as a secondary marker of Pb shot exposure. An avian physiologically based extraction test (PBET) was used to determine pellet dissolution rate and bioaccessible concentrations of Pb, Sb, As, and Sn in a simulated gizzard environment. Of the three trace elements, only Sb concentrations (44–302 μg/mL) extracted into the gizzard solution were greater than environmental background levels (US soil average 0.48 μg/g); thus, no natural source likely provides this amount of Sb. Therefore, there is evidence that Sb can be extracted from Pb shot in bird gizzards at detectable concentrations (above natural background). While further studies are needed to delineate the mechanisms of absorption and distribution, this study lends credence to the hypothesis that Sb may be a useful marker of Pb shot exposure in biological tissues, particularly when Pb pellets are not present nor observed in avian tissues.

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.

Traffic-related distribution of antimony in roadside soils

Vehicular emissions have become one of the main source of pollution of urban soils; this highlights the need for more detailed research on various traffic-related emissions and related distribution patterns. Since the banning of asbestos in the European Union, its substitution with antimony (Sb) in brake linings has led to increased inputs of this toxic metalloid to environmental compartments. The objective of this study was to provide detailed information about the spatial distribution patterns of Sb and to assess its mobility and bioavailability. Roadside soils along an arterial road (approx. 9000 vehicles per day) in Cologne (Germany) were studied along five transects, at four soil depths and at seven sampling points set at varying distances from the road (n = 140). For all samples, comprehensive soil characterization was performed and inverse aqua regia-extractable trace metal content was determined being pseudo-total contents. Furthermore, for one transect, also total Sb and a chemical sequential extraction procedure was applied (n = 28). Pseudo-total Sb for all transects decreased significantly with soil depth and distance from the road, reflecting a distribution pattern similar to that of other trace metals associated with brake lining emissions. Conversely, metals associated with exhaust emissions showed a convex distribution. The geochemical fractionation of Sb revealed the following trends: i) non-specifically sorbed Sb was <5%; ii) specifically sorbed Sb was only detected within 1 m distance from the road and decreased with depth; iii) Sb associated with poorly-crystalline Fe oxides decreased with distance from the road; and iv) content of Sb bounded to well-crystalline Fe oxides, and Sb present in the residual fraction remained relatively constant at each depth. Consequently, roadside soils appear to inhibit brake lining-related Sb contamination, with significant but rather low ecotoxicological potential for input into surface and groundwater.

Organically complexed iron enhances bioavailability of antimony to maize (Zea mays) seedlings in organic soils

Antimony (Sb) is a metalloid belonging to group 15 of the periodic table. Chemical similarities between arsenic (As) and Sb produce concerns about potential health effects of Sb and enrichment in the environment. Antimony is found in oxic environments predominately as an oxyanionic species, antimonite (Sb[OH](6-)). As a result of its net negative charge, Sb[OH](6-) was not initially predicted to have strong interactions with natural organic matter. Oxyanionic species could bind the negatively charged organic matter via a ternary complexation mechanism, in which cationic metals mediate the strong association between organic matter functional groups and oxyanions. However, these interactions are poorly understood in how they influence the bioavailability of oxyanionic contaminants to plants. Iron (Fe) additions to organic soils have been found to increase the number of organically complexed Fe sites suitable for Sb exchange, resulting in a reduced bioavailable fraction of Sb. The bioavailability of Sb to maize seedlings as a function of organically complexed Fe was examined using a greenhouse study. A significant increase in plant tissue Sb was observed as organically complexed Fe increased, which was not predicted by methods commonly used to assess bioavailable Sb. Extraction of soils with organic acids common to the maize rhizosphere suggested that organic acid exudation can readily mobilize Sb bound by organic Fe complexes.

Application of hyphenated techniques in speciation analysis of arsenic, antimony, and thallium

Due to the fact that metals and metalloids have a strong impact on the environment, the methods of their determination and speciation have received special attention in recent years. Arsenic, antimony, and thallium are important examples of such toxic elements. Their speciation is especially important in the environmental and biomedical fields because of their toxicity, bioavailability, and reactivity. Recently, speciation analytics has been playing a unique role in the studies of biogeochemical cycles of chemical compounds, determination of toxicity and ecotoxicity of selected elements, quality control of food products, control of medicines and pharmaceutical products, technological process control, research on the impact of technological installation on the environment, examination of occupational exposure, and clinical analysis. Conventional methods are usually labor intensive, time consuming, and susceptible to interferences. The hyphenated techniques, in which separation method is coupled with multidimensional detectors, have become useful alternatives. The main advantages of those techniques consist in extremely low detection and quantification limits, insignificant interference, influence as well as high precision and repeatability of the determinations. In view of their importance, the present work overviews and discusses different hyphenated techniques used for arsenic, antimony, and thallium species analysis, in different clinical, environmental and food matrices.

Relevance of Sb(III), Sb(V), and Sb-containing nano-particles in urban atmospheric particulate matter

A quick and reliable analytical method for the separation and quantification of extractable Sb(III) and Sb(V) in atmospheric particulate matter (PM) by ion chromatography(IC)-inductively coupled plasma-mass spectrometry (ICP-MS) has been optimized, validated on pairs of real, equivalent PM(10) samples and applied to a field monitoring campaign in a urban site. Both Sb(III) and Sb(V) forms were detected in real samples with Sb(III)/Sb(V) ratios up to 1.5. These two Sb species accounts only for a portion, of variable magnitude, of the total extractable Sb (10-70%); anyway, no other soluble Sb species were detected in the samples. The analysis of size-segregated samples collected by a 13-stage impactor showed that the recovery of [Sb(III) + Sb(V)] versus total extractable Sb is almost quantitative in the coarse fraction while it is below than 10% in the fine fraction. In the extracted solution from particles below 1 mum we could highlight the presence of Sb-containing suspended solid nano-particles, which probably constitute the missing fraction. The contribution of nano-particles can be estimated as the difference between ICP-MS and IC-ICP-MS data, as small size solid bodies are able to pass through the nebulizer and reach the plasma torch, while they are retained by the chromatographic column. The aggregation state of these nano-particles seems to be easily altered when they are suspended in a water solution; a similar behavior could be hypothesized when in contact with biological fluids. It has been confirmed that brake pad abrasion is the prevalent source of Sb(III) in PM and that Sb(V) may be formed by oxidation during the braking processes. Differing from other environmental matrices, there is no evidence of any spontaneous oxidative conversion within the two species.

Methylantimony and -arsenic species in sediment pore water tested with the sediment or fauna incubation experiment

In this study, the speciation of arsenic (As) and antimony (Sb) across a water-sediment interface and the formation of mono-, di-, and trimethylated species overtime in a microfiltered pore water solution were examined. We used an experimental technique, known as the sediment or fauna incubation experiment (SOFIE), which enables the determination of chemical speciation across redox zones in undisturbed systems. Five different incubation experiments were run: Over a 76 day incubation period, pore water was sampled and speciated 5 times. These experiments revealed the complete methylated species pattern for arsenic and antimony in the microfiltered sediment pore water. This constitutes the first report of methylated As and Sb species in a true pore water solution of sediments. Predominant organic species were dimethylantimony (DMSb up to 2.7 microg/L) and dimethylarsenic (DMAs up to 4.3 microg/L) followed by monomethylated species (MMAs and MMSb). These data (i) indicate that methylation significantly influences the translocation of As and Sb in sediments, (ii) demonstrate good agreement between the occurrence of methylantimony and the occurrence of methylarsenic in the pore water, (iii) reveal that As transformation in sediments is faster than Sb transformation but is more susceptible to disturbances from acidification, and (iv) regarding the translocation of these elements and antimony in particular, methylation is clearly a relevant, and perhaps as yet underestimated, factor.

Speciation analysis of antimony in extracts of size-classified volcanic ash by HPLC–ICP-MS

Although there is concern about the presence of toxic elements and their species in environmental matrices, for example water, sediment, and soil, speciation analysis of volcanic ash has received little attention. Antimony, in particular, an emerging element of environmental concern, has been less studied than other potentially toxic trace elements. In this context, a study was undertaken to assess the presence of inorganic Sb species in ash emitted from the Copahue volcano (Argentina). Antimony species were extracted from size-classified volcanic ash (<36 microm, 35-45 microm, 45-150 microm, and 150-300 microm) by use of 1 mol L(-1) citrate buffer at pH 5. Antimony(III) and (V) in the extracts were separated and quantified by high-performance liquid chromatography combined on-line with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Antimony species concentrations (microg g(-1)) in the four fractions varied from 0.14 to 0.67 for Sb(III) and from 0.02 to 0.03 for Sb(V). The results reveal, for the first time, the occurrence of both inorganic Sb species in the extractable portion of volcanic ash. Sb(III) was always the predominant species.