Arsenic speciation of terrestrial invertebrates

Tissue Distribution and Toxicological Risk Assessment of Mercury and Other Elements in Northern Populations of Wolverine (Gulo gulo)

Wolverines are facultative scavengers that feed near the top of terrestrial food chains. We characterized concentrations of mercury and other trace elements in tissues of wolverine from a broad geographic area, representing much of their contemporary distribution in northwestern North America. We obtained tissues from 504 wolverines, from which mercury was measured on muscle (n = 448), kidney (n = 222), liver (n = 148), hair (n = 130), and brain (n = 52). In addition, methylmercury, seven trace elements (arsenic, cadmium, chromium, cobalt, lead, nickel, selenium), and arsenic compounds were measured on a subset of samples. Concentrations of mercury and other trace elements varied between tissues and were generally highest in kidney compared to brain, liver and muscle. Mercury was predominately as methylmercury in brain and muscle, but largely as inorganic mercury in liver and kidney. Mercury concentrations of hair were moderately correlated with those of internal tissues (Pearson r = 0.51-0.75, p ≤ 0.004), making hair a good non-lethal indicator of broad spatial or temporal differences in mercury exposure to wolverine. Arsenobetaine was the dominant arsenic compound identified in tissues, and arsenite, arsenocholine and dimethylarsinic acid were also detected. A preliminary risk assessment suggested the cadmium, lead, mercury, and selenium concentrations in our sample of wolverines were not likely to pose a risk of overt toxicological effects. This study generated a comprehensive dataset on mercury and other trace elements in wolverine, which will support future contaminants study of this northern terrestrial carnivore.

Arsenic and mercury exposure in different insect trophic guilds from mercury mining areas in Mexico

The exposure to arsenic and mercury in various insect trophic guilds from two mercury mining sites in Mexico was assessed. The two study sites were La Laja (LL) and La Soledad (LS) mines. Additionally, a reference site (LSR) was evaluated for LS. The terrestrial ecosystem was studied at LL, whereas both the terrestrial ecosystem and a stream called El Cedral (EC) were assessed at LS. The study sites are situated in the Biosphere Reserve Sierra Gorda (BRSG). Mercury vapor concentrations were measured with a portable analyzer, and concentrations of arsenic and mercury in environmental and biological samples were determined through atomic absorption spectrophotometry. Both pollutants were detected in all terrestrial ecosystem components (soil, air, leaves, flowers, and insects) from the two mines. The insect trophic guilds exposed included pollinivores, rhizophages, predators, coprophages, and necrophages. In LS, insects accumulated arsenic at levels 29 to 80 times higher than those found in specimens from LSR, and 10 to 46 times higher than those from LL. Similarly, mercury exposure in LS was 13 to 62 times higher than LSR, and 15 to 54 times higher than in LL. The analysis of insect exposure routes indicated potential exposure through air, soil, leaves, flowers, animal prey, carrion, and excrement. Water and sediment from EC exhibited high levels of arsenic and mercury compared to reference values, and predatory aquatic insects were exposed to both pollutants. In conclusion, insects from mercury mining sites in the BRSG are at risk.

Methylation and bio-accessibility assessment of arsenate in crickets (Gryllusbimaculatus)

The ability of an organism to biomethylate toxic inorganic arsenic (As) determines both, the amount of As available for uptake higher up the food chain and the toxicity of bioavailable As. An exposure study was conducted to determine ability of farmed crickets to metabolize dietary arsenate. Crickets were exposed to 1.3 ± 0.1, 5.1 ± 2.5 and 36.3 ± 5.6 mg kg-1 dietary arsenate and quantitation of total As showed retention of 0.416 ± 0.003, 1.3 ± 0.04 and 2.46 ± 0.09 mg kg-1, respectively. Speciation analysis revealed that crickets have well developed ability to biomethylate dietary arsenate and the most abundant methylated As compound was DMA followed by MMA, TMAO and an unknown compound. Arsenobetaine, although present in all feed, control and As-rich, was measured only in the control crickets. To assess the bio-accessibility of the As species, crickets were subjected to simulated gastrointestinal digestion. The results showed that majority of As was extracted in saliva, followed by gastric and intestinal juice, which mass fraction was equal to residue. Over 78% of total As was shown to be bio-accessible with methylated species reaching 100% and iAs over 79% bio-accessibility. Additionally, arsenite and arsenate have shown different distributions between sequential leachate solutions. Bioaccumulation of As was observed in the studied crickets although it does not seem to occur to the same extent at higher exposure levels.

Mixed effects and co-transfer of CeO2 NPs and arsenic in the pakchoi-snail food chain

Nanomaterial application in agriculture offers novel solutions for soil arsenic (As) pollution control, yet safety along the food chain is of concern. We comprehensively assessed CeO2 nanoparticles (NPs) foliar application effects on As uptake by pakchoi and their presence in the pakchoi-snail food chain. CeO2 NPs reduced As transfer from pakchoi roots to shoots by 37.9%, lowered As in snail foot by 39%, and halved human As exposure risk. The NPs alleviated pakchoi shoot As toxicity by regulating antioxidants, enhancing water use efficiency, and photosynthesis. CeO2 +As treatment raised GSH/GSSG ratios by 38.92%- 167.54%, leading to an increased AsIII/AsV ratio and inorganic As detoxification compared to As alone. Metabolomics revealed CeO2's rapid As response via phosphatidylinositol signaling. The enzyme-like activity of CeO2 NPs may drive these effects. While CeO2 foliar application accumulated Ce on pakchoi leaves, > 99% of Ce was excreted following snail consumption. Ce transfer from pakchoi leaves to snail foot was minimal (trophic transfer factor ∼0.00007) due to limited bioavailability. The target hazard quotient of Ce in pakchoi shoot (1.21 ± 0.18) and snails (0.0016 ± 0.0004) indicated low exposure risk, suggesting a 'risk filter' effect for CeO2. Our results contribute to the safe and sustainable application of CeO2 NPs in the future implication.

Robust, reliable and quantitative sensing of aqueous arsenic species by Surface-enhanced Raman Spectroscopy: The crucial role of surface silver ions for good analytical practice

Arsenic speciation analysis is important for pollution and health risk assessment. Surface-enhanced Raman Spectroscopy (SERS) is supposed to be a promising detection technology for arsenic species owing to the unique fingerprints. However, further application of SERS is hampered by its poor repeatability. Herein, the role of surface silver ions on colloidal Ag was revealed in SERS analysis of arsenic species. Arsenic species were adsorbed on Ag nanoparticles (Ag NPs) driven by surface silver ions and were simultaneously sensed by the SERS "hot spots" generated from the aggregation of Ag NPs. So, the inconsistent SERS activities of Ag NPs synthesized from different batches can be significantly improved by modifying external silver ions onto Ag NPs (AgNPs@Ag⁺), Specific binding affinity of surface silver ions to arsenic species generated higher sensitivity (detection limit, 4.0 × 10^-11 mol L^-1 for arsenite, 8.0 × 10^-11 mol L^-1 for arsenate), wider linear range, faster response, cleaner spectra background and better reproducibility. Batch-to-batch reproducibility was significantly improved with a variation below 3.1%. The method was also demonstrated with drinking and environmental water with adequate recovery and high interference resistance. Our findings displayed good analytical practice of the surface silver ions derived SERS method and its great potential in the rapid detection of hazardous materials.

Ecological Responses of Maize Rhizosphere to Antibiotics Entering the Agricultural System in an Area with High Arsenicals Geological Background

Metal(loid)s can promote the spread and enrichment of antibiotic resistance in the environmental ecosystem through a co-selection effect. Little is known about the ecological effects of entering antibiotics into the environment with long-term metal(loid)s' resistance profiles. Here, cow manure containing oxytetracycline (OTC) or sulfadiazine (SA) at four concentrations (0 (as control), 1, 10, and 100 mg/kg) was loaded to a maize cropping system in an area with high a arsenicals geological background. Results showed that exogenous antibiotics entering significantly changed the nutrient conditions, such as the concentration of nitrate nitrogen, ammonium nitrogen, and available phosphorus in the maize rhizosphere soil, while total arsenic and metals did not display any differences in antibiotic treatments compared with control. Antibiotics exposure significantly influenced nitrate and nitrite reductase activities to reflect the inhibition of denitrification rates but did not affect the soil urease and acid phosphatase activities. OTC treatment also did not change soil dehydrogenase activities, while SA treatment posed promotion effects, showing a tendency to increase with exposure concentration. Both the tested antibiotics (OTC and SA) decreased the concentration of arsenite and arsenate in rhizosphere soil, but the inhibition effects of the former were higher than that of the latter. Moreover, antibiotic treatment impacted arsenite and arsenate levels in maize root tissue, with positive effects on arsenite and negative effects on arsenate. As a result, both OTC and SA treatments significantly increased bioconcentration factors and showed a tendency to first increase and then decrease with increasing concentration. In addition, the treatments decreased translocation capacity of arsenic from roots to shoots and showed a tendency to increase translocation factors with increasing concentration. Microbial communities with arsenic-resistance profiles may also be resistant to antibiotics entering.

Arsenic speciation analysis in honey bees for environmental monitoring

Arsenic can be toxic to living organisms, depending not only on the concentration, but also its chemical form. The aim of this study was to determine arsenic concentrations and perform arsenic speciation analysis for the first time in honeybees, to evaluate their potential as biomonitors. Highest arsenic concentrations were determined in the vicinity of coal fired thermal power plants (367 µg kg^-1), followed by an urban region (213 µg kg^-1), with much lower concentrations in an industrial city (28.8 µg kg^-1) and rural areas (41 µg kg^-1). Until now, honey bees have never been used to study different arsenic species in the environment. For this reason, four extraction procedures were tested: water, hot water at 90 °C, 20% methanol, and 1% formic acid. Water at 90 °C was able to extract more than 90% of the total arsenic from honey bee samples. Inorganic arsenic (the sum of arsenite and arsenate) accounted for 95% of arsenic species in bees from three locations, except the industrial city, where it represented only 80% of arsenic species, while 15% was present as DMA.

Environmental monitoring of trace elements and evaluation of environmental impacts to organisms near a former uranium mining site in Nigyo-toge, Japan

This study was conducted to find out characteristics of trace element levels and those impacts to organisms at a former uranium (U) mining site. Concentrations of trace elements (Li, Mg, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Mo, Cd, Cs, Ba, Pb, Bi, and U) were determined in sediments, water, and three organism types (insects, frogs, and newts) from three zones in the former U mining site, Ningyo-toge in Japan. Concentrations of As and U in the sediments and water samples were the highest at the mill tailings pond (MP) site, where post-U extraction remnants have been accumulated. Additionally, among the organisms analyzed the highest concentrations of these elements/isotopes were found in newts from MP. Considering data analyses of the whole-body element concentrations, bioaccumulation factors, and δ¹⁵N values for the organisms, it was concluded that newts might be the most vulnerable species in this location. Further monitoring and more accurate evaluation of the ecological impacts are preferred for this former U mining site.

Medicinal Earthworm: Speciation and Bioaccessibility of Arsenic and Its Potential Health Risks

Arsenic in environmental health has caused public concerns all over the world. However, high levels of arsenic residues in medicinal animals have not received enough attention. Medicinal earthworms are consumed widely in China, but its arsenic potential health risks to humans are unknown. This work investigated the total concentration, bioaccessibility, and speciation of arsenic in earthworms by ICP-MS and HPLC-ICP-MS to evaluate its potential health risks to humans. Arsenic was found in all earthworms at concentrations ranging from 0.4 to 53.6 mg kg⁻¹. The bioaccessibility of arsenic (bAs) varied significantly and ranged from 12.1 to 69.1%, with inorganic arsenic (iAs, including As(III) and As(V)) as the predominant species. Furthermore, a small amount of arsenobetaine (AB) was found. The estimated daily intake dose (EDI), hazard quotient (HQ), and carcinogenic risk (CR) of arsenic in most of the samples exceeded the safe threshold level. Results from this study indicated that the potential health risks by the consumption of earthworms may not be negligible. Herein, recommendations for the use of earthworms and regulatory recommendations for arsenic limit standards were proposed. This study reminds us that more control and monitoring of arsenic in medicinal animals should be carried out.

Recent Advances in Colorimetric Detection of Arsenic Using Metal-Based Nanoparticles

Nowadays, arsenic (III) contamination of drinking water is a global issue. Laboratory and instrument-based techniques are typically used to detect arsenic in water, with an accuracy of 1 ppb. However, such detection methods require a laboratory-based environment, skilled labor, and additional costs for setup. As a result, several metal-based nanoparticles have been studied to prepare a cost-effective and straightforward detector for arsenic (III) ions. Among the developed strategies, colorimetric detection is one of the simplest methods to detect arsenic (III) in water. Several portable digital detection technologies make nanoparticle-based colorimetric detectors useful for on-site arsenic detection. The present review showcases several metal-based nanoparticles that can detect arsenic (III) colorimetrically at a concentration of ~0.12 ppb or lower in water. A literature survey suggests that biomolecule-based metal nanoparticles could serve as low-cost, facile, susceptible, and eco-friendly alternatives for detecting arsenic (III). This review also describes future directions, perspectives and challenges in developing this alternative technology, which will help us reach a new milestone in designing an effective arsenic detector for commercial use.

Assessment of legacy mine metal contamination using ants as indicators of contamination

Most legacy mines contributed to contamination of the environment before and after cessation of mining. Contamination from waste rock, slag and tailings can introduce large concentrations of metals and metalloids to the surface soil and downstream sediments. Since ants are able to accumulate metals in their bodies, we investigated the possibility of using the elemental compositions of ants as indicators of metals at legacy mines developed on ores rich in copper (Cu), zinc (Zn), arsenic (As), silver (Ag) and lead (Pb). Our results showed the concentrations of manganese (Mn) and Cu in ants were not significantly different between mine and reference samples and only Zn was significantly different between contaminated and reference areas. Crematogaster spp. and Notoncus spp. from reference areas accumulated larger concentrations of metals in their bodies compared to ants from the mine. Ants accumulated metals in different parts of their bodies. The abdomen was the main site for accumulation of Mn, iron (Fe) and Zn. Mandibles were only associated with accumulation of Zn. Copper and Pb showed no area of preferential accumulation and traces were detected in the whole body of the ants. Ants from five genera had similar regions for metal accumulation. The exoskeleton did not contribute to accumulation of metals; instead all metals were stored in internal organs. Not all genera were suitable for use as indicators; only Iridomyrmex spp. and Ochetellus spp. accumulated larger amount of metals in mine samples compared to reference samples.

Portable smartphone-integrated paper sensors for fluorescence detection of As(III) in groundwater

Arsenic contamination in groundwater is a supreme environmental problem, and levels of this toxic metalloid must be strictly monitored by a portable, sensitive and selective analytical device. Herein, a new system of smartphone-integrated paper sensors with Cu nanoclusters was established for the effective detection of As(III) in groundwater. For the integration system, the fluorescence emissive peak of Cu nanoclusters at 600 nm decreased gradually with increasing As(III) addition. Meanwhile, the fluorescence colour also changed from orange to colourless, and the detection limit was determined as 2.93 nM (0.22 ppb) in a wide detection range. The interfering ions also cannot influence the detection selectivity of As(III). Furthermore, the portable paper sensors based on Cu nanoclusters were fabricated for visual detection of As(III) in groundwater. The quantitative determination of As(III) in natural groundwater has also been accomplished with the aid of a common smartphone. Our work has provided a portable and on-site detection technique toward As(III) in groundwater with high sensitivity and selectivity.

Arsenic speciation in the bracket fungus Fomitopsis betulina from contaminated and pristine sites

Uptake, distribution and speciation of arsenic (As) were determined in the bracket fungus Fomitopsis betulina (previously Piptoporus betulinus), commonly known as the birch polypore, collected from a woodland adjacent to a highly contaminated former mine in the Southwest UK and at an uncontaminated site in Quebec, Canada, with no past or present mining activity. The fruiting body was divided into cap, centre and pores representing the top, middle and underside to identify trends in the distribution and transformation of As. Total As, determined by inductively coupled plasma-mass spectrometry (ICP-MS), was approximately tenfold higher in the mushroom from the contaminated compared to the uncontaminated site. Overall, accumulation of As was low relative to values reported for some soil-dwelling species, with maximum levels of 1.6 mg/kg at the contaminated site. Arsenic speciation was performed on aqueous extracts via both anion and cation high-performance liquid chromatography-ICP-MS (HPLC-ICP-MS) and on whole dried samples using X-ray absorption near edge structure (XANES) analysis. Seven As species were detected in F. betulina from the contaminated site by HPLC-ICP-MS: arsenite (As^III), arsenate (As^V), dimethylarsinate (DMA^V), methylarsonate (MA^V), trimethylarsine oxide (TMAO), tetramethylarsonium ion (Tetra) and trace levels of arsenobetaine (AB). The same As species were observed at the uncontaminated site with the exception of TMAO and Tetra. Arsenic species were localized throughout the fruiting body at the contaminated site, with the cap and pores containing a majority of As^V, only the cap containing TMAO, and the pores containing higher concentrations of DMA^V and MA^V as well as tetra and a trace of AB. XANES analysis demonstrated that the predominant form of As at the contaminated site was inorganic As^III coordinated with sulphur or oxygen and As^V coordinated with oxygen. This is the first account of arsenic speciation in F. betulina or any fungi of the family Fomitopsidaceae.

Facing the threat: common yellowjacket wasps as indicators of heavy metal pollution

We investigated the common wasp, Vespula vulgaris as a bioindicator and biomonitor of metals in the industrial area. Using traps, we collected 257 yellowjackets along a pollution gradient in the Harjavalta Cu-Ni smelter in Southwest Finland. Our method detected metal elements such as arsenic (As), cobalt (Co), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), zinc (Zn), and mercury (Hg) in wasps. The data analyses revealed V. vulgaris can be a proper indicator for As, Cd, Co, Cu, Ni, and Pb, rather than for Fe and Zn contamination. Body burdens of As, Cd, Co, Cu, Ni, and Pb decreased with an increase in distance from smelter. Enrichment factor (EF) followed the pattern Pb ˃ Cd ˃ As ˃ Co ˃ Cu ˃ Ni. The highest bioaccumulation (BAF) values were revealed for Cd (5.9) and the lowest for Pb (0.1). Specially designed software (WaspFacer) allowed revealing body burdens of As, Cd, Co, Cu, Ni, and Pb to be associated with rather smaller than more asymmetric facial colour markings in yellowjackets. These results add to the body of literature on how heavy metal contaminants can have tangible phenotypic effects on insects and open future opportunities for using wasps as indicators of metal pollution.

Application of stable isotopes to the bioaccumulation and trophic transfer of arsenic in aquatic organisms around a closed realgar mine

The bioaccumulation and trophic transfer of As along food webs in freshwater ecosystems remain largely unknown. In this study, multiple environmental and biological samples were collected from a closed realgar mining area in South China. The As concentrations in the surface water, sediments and soils in the mining area were 0.62-3293 μg/L, 9.53-4543 mg/kg and 7.32-5008 mg/kg, respectively, and gradually decreased with distance from the central mining sites, indicating that historic As mining activities had an eminent impact on As contamination around the mine. The As concentrations in aquatic organisms ranged from 0.60 mg/kg to 45.75 mg/kg and varied markedly among sites and species, reflecting the influence of various physiologic and environmental factors. Arsenic species identified by liquid chromatography inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) were mainly organic, comprising 8% to 66% of the total As. Both the proportions and concentrations of inorganic As were positively correlated with total As. This correlation could be attributed to the higher assimilation and accumulation of inorganic As or the lower biotransformation ability of inorganic As with the increasing total As in the studied organisms. Values of δ¹³C and δ¹⁵N in aquatic organisms ranged from -30.59‰ to -15.07‰ and from 4.31‰ to 12.98‰, respectively, indicating multiple trophic levels and variety in the diet sources of these organisms. The δ¹⁵N increased distinctly in the order of planktivorous<herbivorous<omnivorous<carnivorous, which is generally consistent with the increasing trophic levels in the freshwater ecosystem. No significant correlation was observed between As concentrations and δ¹⁵N in the freshwater organisms, suggesting no biomagnification of As in the food web.

Soil Physicochemical Properties, Metal Deposition, and Ultrastructural Midgut Changes in Ground Beetles, Calosoma chlorostictum, under Agricultural Pollution

Unsustainable agricultural practices that minimize soil organic matter can promote the removal of heavy metal pollutants into the food chain. Such polluted soils can release contaminants into the groundwater, which leads to accumulation in plant tissue that is transferred to animals, birds, insects, and humans. Biomonitors of soil pollution with heavy metals can be identified by the ground beetles Calosoma chlorostictum (Coleoptera: Carabidae) as bioindicators of soil quality and its yield sustainability. The experiment was performed on two sites in Zagazig City (30.62° N, 31.44° E), Egypt. The physicochemical parameters indicated that soil moisture and organic matter had the highest differences in the polluted agricultural soil compared to the reference soil. However, there were no significant differences in chloride content. The atomic absorption analysis exhibited the highest concentration recorded for arsenic (As) and the lowest for selenium (Se) in the polluted soil and the insect’s midgut. Meanwhile, the differences between heavy metal concentrations in the total soil and midgut of C. chlorostictum from current sites indicated that the highest differences were in aluminum (Al) and mercury (Hg), while arsenic (As) and cadmium (Cd) were the lowest. Furthermore, the correlation between heavy metal concentrations in the soil and insect midgut was highest in As, while the lowest correlation was noticed in Al. We used transmission electron microscopy (TEM) that showed a more considerable disturbance in the C. chlorostictum midgut epithelial layer collected from the agricultural area than in the insects collected from the reference area. Evident ultrastructural alterations showed a rupture and distortion of microvilli, destruction of the columnar and regenerative cells, large separation between epithelial cells, and stretching of the cellular axis, as a result of which the lumen became very narrow. Moreover, a lot of vacuoles with little enzyme secretion were observed in the columnar epithelial cells. In addition, other manifestations due to pollution with heavy metals such as a pyknotic nucleus with abnormal chromatin, cytoplasmic vacuolization, disruptions, and vacuolation of mitochondria were detected, as well as the appearance of electron-dense vesicles, a lot of lysosomes, large myelin figures, and dilation of the rough endoplasmic reticulum on account of soil contamination. Potential counteractive health influence in such applications could be avoided if the soil was adequately treated.

Arsenic transformation mediated by gut microbiota affects the fecundity of Caenorhabditis elegans

Arsenic biotransformation has been discovered in guts of soil invertebrates. Reproduction of invertebrates is sensitive to arsenic contamination in soils. However, little is known about the impact of gut microbe-mediated arsenic biotransformation on the fecundity of invertebrates. Here, Caenorhabditis elegans was firstly pre-fed with Escherichia coli BL21 possessing the capability of reducing arsenate [As(V)] or BL21M having the ability to reduce As(V) and methylate arsenite [As(III)], then inoculated worms were transferred to inactive E. coli AW3110 (harboring no arsenic transformation gene)-seeded plates treated with As(V) at different concentrations. Quantification of gut microbes showed that both E. coli BL21 and BL21M stably colonized in the guts after worms were cultured on inactive E. coli AW3110-seeded plates for 72 h. The analysis of arsenic species indicated that there was As(III) in C. elegans guts colonized with E. coli BL21, As(III) and dimethylarsinic acid [DMAs(V)] in C. elegans guts with E. coli BL21M exposed to As(V) for 6 h. After treatment of 100 μM As(V), decrease in brood sizes was observed for worms that were colonized with E. coli BL21 or BL21M compared to that with AW3110 in the guts. The levels of vitellogenin (VTG), glutathione S-transferases (GST) and superoxide dismutase (SOD), closely linked to reproduction and antioxidation-linked indicators, were the highest in worms whose guts colonized with E. coli BL21, followed by worms colonized with E. coli BL21M and worms colonized with inactive E. coli AW3110 exposed to As(V). Our results indicated the toxic impact of As(III) and DMAs(V) produced by gut microbes on reproduction of C. elegans. The work provides novel insight into the interplay between arsenic biotransformation mediated by gut microbes and the host fecundity in soils.

A Chemically Safe Way to Produce Insect Biomass for Possible Application in Feed and Food Production

Black soldier fly (Hermetia illucens, HI, Diptera, Stratiomydae) has great potential as a food and feed ingredient in the European Union (EU). The production of insects as livestock feed or as food ingredients requires strict monitoring of the content of potentially toxic elements (PTEs) in the growth substrate, to meet the security requirements. This study aims to investigate the presence of PTEs, like cadmium, lead, mercury, arsenic, and nickel, in HI prepupae and in their growth substrates based on coffee roasting by-product and microalgae Schizochytrium sp. and Isochrysis sp. Analyses were carried out via graphite furnace atomic absorption spectrophotometry for Cd, Pb, Ni, and As, and via Direct Mercury Analyzer for Hg. All element concentrations found in growth substrates were below the legal limit of undesirable substances in animal feed (2002/32/EC). Elements concentrations in HI prepupae were in the range (mg kg-1 wet weight) of 0.072 to 0.084 for Cd, 0.018 to 0.026 for Pb, 0.010 to 0.032 for Hg, 0.036 to 0.047 for As, and 0.18 to 0.76 for Ni. Even if HI prepupae accumulated Cd, Pb, and Hg, our results indicated that the risk of exposure to PTEs from HI prepupae consumption is relatively low and in compliance with EU regulations.

Arsenic characteristics in the terrestrial environment in the vicinity of the Shimen realgar mine, China

In this study, multiple types of samples, including soils, plants, litter and soil invertebrates, were collected from a former arsenic (As) mine in China. The total As concentrations in the soils, earthworms, litter and the aboveground portions of grass from the contaminated area followed the decreasing order of 83-2224 mg/kg, 31-430 mg/kg, 1-62 mg/kg and 2-23 mg/kg, respectively. X-ray absorption near-edge structure (XANES) analysis revealed that the predominant form of As in the soils was arsenate (As(V)), while no arsenite (As(III)) was detected. In the grass and litter of the native plant community, inorganic As species (As(V) and As(III)) were the main species, while minor amounts of DMA, MMA, AsC, and an unknown As species were also detected in the extracts analyzed with high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The As speciation and As concentrations varied with the plant species, and very high As levels (197-584 mg/kg) and proportions of inorganic As (>99%) were found in two As-hyperaccumulating ferns, Pteris vittata and Pteris cretica. The major As species extracted from earthworms were inorganic, with proportions of 51-53% As(III) and 38-48% As(V). AsB was the only organic species present in the earthworm samples, although at low proportions (<8.99%). The internal bioconversion of other As species is hypothesized to contribute greatly to the formation and accumulation of AsB in earthworms, although the direct external absorption of organic As from soils might be another source. This study sheds light on the potential sources of complex organoarsenicals, such as AsB, in terrestrial organisms.

Experimental manipulation of dietary arsenic levels in great tit nestlings: Accumulation pattern and effects on growth, survival and plasma biochemistry

Arsenic (As) is a ubiquitous metalloid classified as one of the most hazardous substances, but information about its exposure and effects in free-living passerines is lacking. The aim of this study is to elucidate the effect of an As manipulation experiment on survival, growth and physiology of great tits (Parus major). Wild P. major nestlings inhabiting an unpolluted area were dosed with water, 0.2 or 1 μg g^-1 d^-1 of sodium arsenite (Control, Low and High As groups), whereas those living in a metal-polluted area were dosed with water (Smelter group). Birds accumulated As in tissues (liver, bone and feathers) in a dose-dependent way. Nestlings exposed to 1 μg g^-1 d^-1 of sodium arsenite showed reduced number of fledglings per successful nest, and those exposed to 0.2 μg g^-1 d^-1 had reduced wing growth, which could have post-fledging consequences such as increased predation risk. These results suggest that the LOAEL for effects on nestling survival and development in great tits is likely equal to or below 1 μg g^-1 d^-1. However, limited effects on the biochemical parameters evaluated were found. It has been shown that As may produce oxidative stress and tissue damage, so further research exploring this issue will be carried out in a future study.

Arsenic concentrations and speciation in wild birds from an abandoned realgar mine in China

Birds are at a higher level in the food chain; however, the potential bioaccumulation and biotransformation of arsenic (As) in birds in As mines has rarely been studied. In this study, four passerine bird species (tree sparrow [Passer montanus], light-vented bulbul [Pycnonotus sinensis], Garrulax canorus [Leucodioptron canorus], and magpie [Pica pica]) were collected from an abandoned As mine in China. The highest recorded As concentrations were 4.95 mg/kg and 51.65 mg/kg in muscles and feathers, respectively. Detection using high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) revealed six As species, including arsenite (As(III)), arsenate (As(V)), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenobetaine (AsB) and arsenocholine (AsC), with the former three species as the dominant (>92%) and the latter three as the minor As species (<6.17%). Further analysis of the selected bird samples using the X-ray absorption near edge structure (XANES) technique revealed the existence of As(III)-tris-glutathione (As(III)-GSH), which can be regarded as equivalent to the non-extractable and unidentified As form in the HPLC-ICP-MS data. Both methods revealed similar patterns of As species in the birds from the As mine, with muscles containing mainly inorganic As and DMA and feathers containing mainly inorganic As. The results of this study contribute to the knowledge regarding As accumulation and speciation in terrestrial organisms.

A Highly Sensitive Enzymatic Catalysis System for Trace Detection of Arsenic in Water

Arsenic (As) is an extremely toxic element that exists in the environment in different chemical forms. The detection of arsenic in potable water remains a challenging task. This study presents a highly sensitive enzymatic catalysis system for trace sensing of inorganic arsenic in water. This is the first enzyme-catalyzed fluorescence assay capable of detecting arsenic at concentrations below the allowable level adopted by the World Health Organization (10 ppb in drinking water). The enzyme catalytically produces fluorescent NADH in the presence of arsenate, which enables facile detection of arsenate at concentrations in the 0-200 ppb range. Calibration curves made at a set time interval allow accurate determination of unknown arsenic samples. This method holds potential for interfacing with automated analytical sampling systems to allow arsenic determinations in environmental health applications.

Deriving water quality criteria for trivalent and pentavalent arsenic

Arsenic (As) is a common trace element whose oxidation states mainly include four types (-3, 0, +3, and +5), and inorganic As(III) and As(V) are regarded as the most commonly existing forms in aqueous environments. Generally, As(III) has a higher toxicity than As(V) due to the different mechanisms in arsenic toxicity. However, there are few studies about the water quality criteria (WQC) of As(III) and As(V) respectively because of the deficiency of arsenic toxicity data coming from diverse taxonomic groups. In this research, eight native Chinese aquatic organisms were adopted to conduct toxicity tests for As(III) and As(V) to supplement the published toxicity data. The species sensitivity distribution (SSD) method on the basis of the Log-normal model which was the most optimal among eight models was applied to derive WQCs of As(III) and As(V). Results showed that crustaceans were the most sensitive to As(III) and As(V) among all tested species, thus they could be a biological indicator, and the influence of pH values on arsenic toxicity was complex and species-specific. Besides, the sensitivity differences between native and non-native species were observed. Finally, a criterion maximum concentration (CMC) of 167 and 384μg/L for As(III) and As(V), and a criterion continuous concentration (CCC) of 42 and 44μg/L for As(III) and As(V) were derived using native species, regardless of pH values. The WQCs were also verified by other two methods of ETX 2.0 and species sensitivity rank.

Colloidal quantum dot chains: self-assembly mechanism and ratiometric fluorescent sensing

Colloidal quantum dot chains self-assembled via the mediation of trithiocyanuric acid (TTCA) and ratiometric fluorescent sensing with blue emitting carbon dots (CDs) for As(iii).

Uptake of Cadmium, Lead and Arsenic by Tenebrio molitor and Hermetia illucens from Contaminated Substrates

Insects have potential as a novel source of protein in feed and food production in Europe, provided they can be used safely. To date, limited information is available on the safety of insects, and toxic elements are one of the potential hazards of concern. Therefore, we aimed to investigate the potential accumulation of cadmium, lead and arsenic in larvae of two insect species, Tenebrio molitor (yellow mealworm) and Hermetia illucens (black soldier fly), which seem to hold potential as a source of food or feed. An experiment was designed with 14 treatments, each in triplicate, per insect species. Twelve treatments used feed that was spiked with cadmium, lead or arsenic at 0.5, 1 and 2 times the respective maximum allowable levels (ML) in complete feed, as established by the European Commission (EC). Two of the 14 treatments consisted of controls, using non-spiked feed. All insects per container (replicate) were harvested when the first larva in that container had completed its larval stage. Development time, survival rates and fresh weights were similar over all treatments, except for development time and total live weight of the half of the maximum limit treatment for cadmium of the black soldier fly. Bioaccumulation (bioaccumulation factor > 1) was seen in all treatments (including two controls) for lead and cadmium in black soldier fly larvae, and for the three arsenic treatments in the yellow mealworm larvae. In the three cadmium treatments, concentrations of cadmium in black soldier fly larvae are higher than the current EC maximum limit for feed materials. The same was seen for the 1.0 and 2.0 ML treatments of arsenic in the yellow mealworm larvae. From this study, it can be concluded that if insects are used as feed materials, the maximum limits of these elements in complete feed should be revised per insect species.

Terrestrial Invertebrate Arsenic Accumulation Associated With an Arsenic Hyperaccumulating Fern, Pteris vittata (Polypodiales: Pteridaceae)

Arsenic (As) can play an important role in the contamination of soils, waters, and air. The toxicity of As to most organisms is well established, but little is known about the interactions between environmental As and terrestrial invertebrates and the fate of As through trophic levels. Pteris vittata L. (Polypodiales: Pteridaceae), a fern that hyperaccumulates arsenic, serves as a potential mechanism to facilitate interactions between environmental arsenic and other biota. We compared invertebrate arsenic concentrations (hereafter as [As]) and bioaccumulation factors associated with soil and fern [As] to elucidate relationships between invertebrate and environmental As exposure. We collected invertebrates in pitfall traps from field sites associated with P. vittata, and identified them to order for whole body arsenic analysis and subsequently family for classification into functional feeding groups. We found that overall [As] in invertebrates increased with soil [As], but not with fern [As]. The absence of a relationship between fern [As] and invertebrate [As] may indicate invertebrates are avoiding the fern. Individual taxonomic groups significantly differed in whole body [As], and individual taxa also varied in their relationship between whole body [As] relative to soil and fern [As]. Overall invertebrate abundance decreased as invertebrate [As] load increased but varied across taxa. One particular herbivore, Callopistria floridensis (Florida fern caterpillar), associated with relatively low environmental As exposure contained over 4,000 mg kg^-1 As. Our results show that As bioaccumulates into higher trophic levels and invertebrate body [As] covary with exposure to naturally occurring environmental [As] associated with P. vittata.

Arsenobetaine: the ongoing mystery

Arsenobetaine (AsB) is a non-toxic organoarsenical identified as a major arsenic species in marine animals and a number of terrestrial mushrooms. Since its first identification nearly 40 years ago, numerous studies investigating the biosynthesis and function of AsB have been carried out, although molecular mechanisms have not been fully elucidated. Where and how is AsB formed? Why do marine animals acquire high concentrations of AsB? This review briefly summarizes the current progress of AsB research toward understanding its origin, function and the putative pathways for its biosynthesis. This paper also suggests potential future studies in the attempt to solve the AsB mystery.

Target induced aggregation of modified Au@Ag nanoparticles for surface enhanced Raman scattering and its ultrasensitive detection of arsenic(iii) in aqueous solution

A highly sensitive and selective detection of As(iii) was reported by target induced aggregation of nanoparticles enhanced Raman spectroscopic technique.

Responses of wild small mammals to arsenic pollution at a partially remediated mining site in Southern France

Partial remediation actions at a former gold mine in Southern France led to a mosaic of contaminated and rehabilitated zones. In this study, the distribution of arsenic and its potential adverse effects on small mammals were investigated. The effectiveness of remediation for reducing the transfer of this element into wildlife was also discussed. Arsenic levels were measured in the soil and in the stomach contents, livers, kidneys, and lungs of four small mammal species (the wood mouse (Apodemus sylvaticus), the Algerian mouse (Mus spretus), the common vole (Microtus arvalis), and the greater white-toothed shrew (Crocidura russula)). The animals were caught at the former extraction site, in zones with three different levels of remediation treatments, and at a control site. Arsenic concentrations in the soil were highly spatially heterogeneous (ranging from 29 to 18,900 μg g(-1)). Despite the decrease in arsenic concentrations in the remediated soils, both wood mice and Algerian mice experienced higher oral exposure to arsenic in remediated zones than in the control area. The accumulated arsenic in their organs showed higher intra-zonal variability than the arsenic distribution in the soil, suggesting that, in addition to remediation processes, other variables can help explain arsenic transfer to wildlife, such as the habitat and diet preferences of the animals or their mobility. A weak but significant correlation between arsenic concentration and body condition was observed, and weak relationships between the liver/kidney/lung mass and arsenic levels were also detected, suggesting possible histological alterations.

Micro x-ray absorption spectroscopic analysis of arsenic localization and biotransformation in Chironomus riparius Meigen (Diptera: Chironomidae) and Culex tarsalis Coquillett (Culicidae)

The distribution and speciation of arsenic (As) were analyzed in individuals of various life stages of a midge, Chironomus riparius, and the mosquito Culex tarsalis exposed to 1000 μg/l arsenate. X-ray absorption spectroscopy (XAS) revealed that C. riparius larvae accumulate As in their midgut, with inorganic arsenate [As(V)] being the predominant form, followed by arsenite [As(III)] and an As-thiol. Reduced concentrations of As in pupal and adult stages of C. riparius indicate excretion of As between the larval and pupal stages. In adults, As was limited to the thorax, and the predominant form was an As-thiol. In Cx. tarsalis, As was not found in high enough concentrations to determine As speciation, but the element was distributed throughout the larva. In adults, As was concentrated in the thorax and eyes of adults. These results have implications for understanding the biotransformation of As and its movement from aquatic to terrestrial environments.

Arsenic species and uptake in amphibians (Rana clamitans and Bufo americanus)

Total arsenic concentrations and the chemical form, or species, of arsenic were determined in amphibians (Rana clamitans and Bufo americanus) collected from a site with elevated arsenic concentrations in Nova Scotia, Canada. Frog legs had significantly elevated total arsenic concentrations at a contaminated site when compared with a nearby background site and a calculation of the estimated daily intake rates of arsenic indicates that both diet (invertebrate intake) and water absorption are important sources of arsenic for these adult organisms. Body burdens of tetramethylarsonium were similar for both the contaminated and background site, with up to 50% of the total arsenic contained in frog legs in the form of the tetramethylarsonium ion.

Arsenic resistance and cycling in earthworms residing at a former gold mine in Canada

Earthworms (Lumbricus castaneous and Dendrodrilus rubidus), their host soils and leaf litter were collected from a former gold mine with widespread arsenic (As) contamination in Nova Scotia, Canada and determined for total and speciated As. Resistance to As toxicity was investigated by measurement of DNA damage in exposed earthworm populations using the comet assay. Arsenobetaine (AB) was observed at low concentration in the earthworms but not in the host soil or leaf litter. Several different organoarsenic species were observed in the leaf litter and only inorganic As was found in the host soils. The results suggest that 1) adaptation to As toxicity in earthworms is widespread and not particular to a single species, 2) AB originates in the earthworm and not the consumed soil or leaf litter and 3) as previously hypothesised (Button et al., 2010), biotransformation of inorganic As to AB is not likely involved in the adaptation.

Arsenic distribution and speciation in Daphnia pulex

Rat Lake, Yellowknife, Northwest Territories, is situated on arsenic-rich tailings from a historical gold mine. The abundant zooplankton species Daphnia pulex in this lake was used to study the impact of arsenic at the base of the freshwater food web; the speciation and distribution of arsenic in D. pulex and its food sources; and the origin of formation of organoarsenicals in freshwater systems. The arsenic concentration in lake water was measured as 0.25 mg L(-1), while the zooplankton organisms contained up to 35 mg kg(-1) d.w. arsenic. Plankton samples were analyzed for arsenic speciation, by using X-ray Absorption Near Edge Structure (XANES) on the whole, dried samples and High Performance Liquid Chromatography coupled to Inductively Coupled Plasma Mass Spectrometry (HPLC-ICP-MS) on water extracts. XANES data suggest that D. pulex mainly contain inorganic arsenicals with 56% of arsenic with +5 oxidation state and 10% of arsenic with +3 oxidation state, but also 34% of organoarsenic compounds that were identified with HPLC-ICP-MS as monomethylarsonate (MMA), dimethylarsinate (DMA), and arsenosugars. The most abundant of the organoarsenicals was the glycerol sugar (Sugar 1). X-ray Fluorescence (XRF) mapping of D. pulex for arsenic distribution showed that arsenic was mainly distributed in the gut of the animal, where its concentration was ten times higher than in the surrounding tissues. Moreover, the analysis of residues from extractions targeting water-soluble and lipid-soluble arsenicals suggested that part of the measured arsenic signal comes from ingested sediments, phytoplankton, or other food sources. These food sources contain inorganic arsenic only, with As(V)-O in phytoplankton and As(III)-S in sediments, suggesting the possibility that the organoarsenicals compounds detected in the tissues of the organism are created by the Daphnia.

Arsenic speciation, distribution, and bioaccessibility in shrews and their food

Shrews (Sorex cinereus) collected at a historic mine in Nova Scotia, Canada, had approximately twice the arsenic body burden and 100 times greater daily intake of arsenic compared with shrews from a nearby uncontaminated background site. Shrews store arsenic as inorganic and simple methylated arsenicals. Much of the arsenic associated with their primary food source, i.e., small invertebrates, may be soil adsorbed to their exoskeletons. A physiologically based extraction test estimated that 47 ± 2% of invertebrate arsenic is bioaccessible in the shrew gastrointestinal tract. Overall, shrews appear to be efficient at processing and excreting inorganic arsenic.

Arsenic speciation in blue mussels (Mytilus edulis) along a highly contaminated arsenic gradient

Arsenic is naturally present in marine ecosystems, and these can become contaminated from mining activities, which may be of toxicological concern to organisms that bioaccumulate the metalloid into their tissues. The toxic properties of arsenic are dependent on the chemical form in which it is found (e.g., toxic inorganic arsenicals vs nontoxic arsenobetaine), and two analytical techniques, high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) and X-ray absorption spectroscopy (XAS), were used in the present study to examine the arsenic species distribution in blue mussels (Mytilus edulis) obtained from an area where there is a strong arsenic concentration gradient as a consequence of mining impacted sediments. A strong positive correlation was observed between the concentration of inorganic arsenic species (arsenic compounds with no As-C bonds) and total arsenic concentrations present in M. edulis tissues (R(2) = 0.983), which could result in significant toxicological consequences to the mussels and higher trophic consumers. However, concentrations of organoarsenicals, dominated by arsenobetaine, remained relatively constant regardless of the increasing As concentration in M. edulis tissue (R(2) = 0.307). XANES bulk analysis and XAS two-dimensional mapping of wet M. edulis tissue revealed the presence of predominantly arsenic-sulfur compounds. The XAS mapping revealed that the As(III)-S and/or As(III) compounds were concentrated in the digestive gland. However, arsenobetaine was found in small and similar concentrations in the digestive gland as well as the surrounding tissue suggesting arsenobetaine may being used in all of the mussel's cells in a physiological function such as an intracellular osmolyte.

Arsenic speciation in plankton organisms from contaminated lakes: transformations at the base of the freshwater food chain

The two complementary techniques high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and X-ray absorption near edge structure (XANES) analysis were used to assess arsenic speciation in freshwater phytoplankton and zooplankton collected from arsenic-contaminated lakes in Yellowknife (Northwest Territories, Canada). Arsenic concentrations in lake water ranged from 7 μg L(-1) in a noncontaminated lake to 250 μg L(-1) in mine-contaminated lakes, which resulted in arsenic concentrations ranging from 7 to 340 mg kg(-1) d.w. in zooplankton organisms (Cyclops sp.) and from 154 to 894 mg kg(-1) d.w. in phytoplankton. The main arsenic compounds identified by HPLC-ICP-MS in all plankton were inorganic arsenic (from 38% to 98% of total arsenic). No other arsenic compounds were found in phytoplankton, but zooplankton organisms showed the presence of organoarsenic compounds, the most common being the sulfate arsenosugar, up to 47% of total arsenic, with traces of phosphate sugar, glycerol sugar, methylarsonate (MMA), and dimethylarsinate (DMA). In the uncontaminated Grace Lake, zooplankton also contained arsenobetaine (AB). XANES characterization of arsenic in the whole plankton samples showed As(V)-O as the only arsenic compound in phytoplankton, and As(III)-S and As(V)-O compounds as the two major inorganic arsenic species in zooplankton. The proportion of organoarsenicals and inorganic arsenic in zooplankton depends upon the arsenic concentration in lakes and shows the impact of arsenic contamination: zooplankton from uncontaminated lake has higher proportions of organoarsenic compounds and contains arsenobetaine, while zooplankton from contaminated area contains mostly inorganic arsenic.

Arsenic speciation in field-collected and laboratory-exposed earthworms Lumbricus terrestris

Mature Lumbricus terrestris were host soils and leaf litter were collected from a former arsenic mine in Devon, UK (Devon Great Consols), a former gold mine in Ontario, Canada (Deloro), and an uncontaminated residential garden in Nottingham, UK. Arsenic concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS) in soils were 16-348 mg kg(-1), 6.0-239 mg kg(-1) in the earthworms and 8.6 mg kg(-1) in leaf litter sampled at Deloro (all dry weight). High performance liquid chromatography (HPLC-ICP-MS) analysis revealed arsenite (As(III)), arsenate (As(V)) and five organoarsenic species; arsenobetaine (AB), methylarsonate (MA(V)), dimethylarsinate (DMA(V)), arsenosugar 1 (glycerol sugar), arsenosugar 2 (phosphate sugar), and trimethylarsineoxide (TMAO) in field-collected L. terrestris. Differences were observed in the variety of organoarsenic species present between field sites. Several organoarsenic species were observed in the leaf litter (DMA(V), arsenosugar 2 and TMAO) but not AB. Depuration resulted in higher concentrations of inorganic As being detected in the earthworm whereas the concentration or variety of organoarsenic species was unchanged. Commercially sourced L. terrestris were exposed to As contaminated soil in laboratory mesocosms (1.0, 98, 183, 236, 324 and 436 mg kg(-1)) without leaf litter and were additionally analyzed using X-ray absorption near edge structure (XANES). Only inorganic As(III) and As(V) was observed. It is proposed that ingestion of leaf litter and symbiotic processes in the natural soil environment are likely sources of organoarsenic compounds in field-collected L. terrestris.

Highly sensitive SERS detection of As3+ ions in aqueous media using glutathione functionalized silver nanoparticles

A highly sensitive surface-enhanced Raman scattering (SERS) platform for the selective trace analysis of As(3+) ions was reported based on glutathione (GSH)/4-mercaptopyridine (4-MPY)-modified silver nanoparticles (AgNPs). Here, GSH conjugated on the surface of AgNPs for specifical binding with As(3+) ions in aqueous solution through As-O linkage and 4-MPY was used as a Raman reporter. When As(3+) ions were added to the system, the binding of As(3+) with GSH resulted in the aggregation of AgNPs, and excellent Raman signal of 4-MPY reporters was obtained which can reflect the concentration of As(3+) indirectly. Under optimal assay conditions, the limit of detection (LOD) was estimated to be as low as 0.76 ppb, which is lower than the WHO defined limit (10 ppb), and an excellent linear range of 4-300 ppb was obtained. The practical application had been carried out for determination of As(3+) in real water samples.

Effects of organic matter and ageing on the bioaccessibility of arsenic

Arsenic-contaminated soils may pose a risk to human health. Redevelopment of contaminated sites may involve amending soils with organic matter, which potentially increases arsenic bioaccessibility. The effects of ageing on arsenic-contaminated soils mixed with peat moss were evaluated in a simulated ageing period representing two years, during which arsenic bioaccessibility was periodically measured. Significant increases (p = 0.032) in bioaccessibility were observed for 15 of 31 samples tested, particularly in comparison with samples originally containing >30% bioaccessible arsenic in soils naturally rich in organic matter (>25%). Samples where percent arsenic bioaccessibility was unchanged with age were generally poor in organic matter (average 7.7%) and contained both arsenopyrite and pentavalent arsenic forms that remained unaffected by the organic matter amendments. Results suggest that the addition of organic matter may lead to increases in arsenic bioaccessibility, which warrants caution in the evaluation of risks associated with redevelopment of arsenic-contaminated land.

Effect of particle size on arsenic bioaccessibility in gold mine tailings of Nova Scotia

Tailings samples from the Goldenville and Montague abandoned gold mines in Nova Scotia, Canada were subjected to bioaccessibility tests to examine the effects of the choice of particle size fraction on the bioaccessibility of arsenic. The proportion of finer grains (<150μm) in this sample set varied from 6.0 to 66wt.%. Samples were sieved to <250, <150, and <45μm particle size fractions. The arsenic bioaccessibility ranged from less than 1.0 to 48%, but no systematic variation was observed (p>0.13) precluding the association of greater percent arsenic bioaccessibility with a specific particle size fraction, method or site. On the other hand, the highest bioaccessible arsenic concentrations (up to 5200mgkg(-1)) were consistently observed in samples sieved to the <45μm particle size, for both the physiologically based extraction test and a glycine-buffered bioaccessibility method (in 89 and 87% of samples tested, respectively). This was due to higher total arsenic concentrations in the same particle size fraction. Grain maps obtained by X-ray absorption spectroscopy indicate that samples with the highest percent arsenic bioaccessibility contain amorphous pentavalent arsenic distributed throughout the sample as well as grains coated with pentavalent arsenic. Arsenic bioaccessibilities lower than 10% were found in samples with encapsulated arsenopyrite and some grains composed primarily of pentavalent arsenic. The <45μm particle size fraction appears to yield conservative (protective) estimates of the bioaccessible dose of arsenic, but wide variations exist in particle size distribution and arsenic bioaccessibility between samples. As well, sieving to <45μm may exclude potentially relevant particles by restricting the study to an average particle size that is smaller than the average size of particles found on human hands, and may unduly influence the resulting bioaccessibility measurements.

Nanogold-based sensing of environmental toxins: excitement and challenges

There have been tremendous advances in the past ten years on the development of various nanomaterials-based sensors for detection of environmental toxins. Nanogold is of special interest because of its unique shape- and size-dependent optical properties, hyper-quenching ability, super surface-enhanced Raman and dynamic light scattering, and surface-modifiability by small organic molecules and biomolecules. These unique optical properties of nanogold have been explored for ultra-sensitive detection, while its surface-modifiability has been explored for selectivity. In general, the nanogold-based sensors are highly selective and sensitive along with simple sample preparation and sensor design. In this review article, we intend to capture some of the recent advances in nanogold-based sensor development and mechanistic studies, especially for bacteria, heavy metals, and nitroaromatic compounds. Undoubtedly, these developments will generate a lot of excitement for environmental scientists and toxicologists as well as the general public.

Arsenic transformations and biomarkers in meadow voles (Microtus pennsylvanicus) living on an abandoned gold mine site in Montague, Nova Scotia, Canada

Arsenic is one of the most widely encountered environmental contaminants because of a number of anthropogenic sources; in Canada the main anthropogenic release of arsenic is from mine tailings ponds. The present study is part of a series of studies to measure chemical and biological effects of exposure for meadow voles (Microtus pennsylvanicus) living on arsenic contaminated sites. Two additional objectives were addressed in the present study: the effect of higher arsenic concentrations compared with previous studies, and the comparison of chemical speciation and biological effects. To obtain the higher environmental concentrations, specimens were collected from a former gold mining site in Montague, NS that contains highly elevated concentrations of arsenic in soils and plants. Meadow voles were collected and their tissues were analyzed for total arsenic to measure uptake, and arsenic speciation to examine the chemical effects of the high arsenic exposure. In addition to the arsenic analysis, a biomonitoring study was undertaken to examine the sub-cellular effects in meadow voles resulting from the elevated arsenic exposure. Meadow voles living on the contaminated site had substantially higher concentrations of total arsenic than animals from the background (reference) location. The extractable arsenic in internal tissues was present mainly as monomethylarsonic acid (up to 14% of total arsenic). A statistically significant relationship was observed between the reduction of glutathione in vole livers and the increase in liver arsenic concentrations, and micronucleated monochromatic red blood cells were also significantly elevated in voles from the arsenic contaminated site. This is one of the few field studies where sub-cellular effects were observed, and the first to show a co-existence of such effects with relatively high proportions of monomethylarsonic acid in voles living near mine tailings.