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Bioaccessibility tests and mineralogical analyses were performed on arsenic-contaminated tailings and soils from gold mine districts of Nova Scotia, Canada, to examine the links between soil composition, mineralogy, and arsenic bioaccessibility. Arsenic bioaccessibility ranges from 0.1% to 49%. A weak correlation was observed between total and bioaccessible arsenic concentrations, and the arsenic bioaccessibility was not correlated with other elements. Bulk X-ray absorption near-edge structure analysis shows arsenic in these near-surface samples is mainly in the pentavalent form, indicating that most of the arsenopyrite (As(1-)) originally present in the tailings and soils has been oxidized during weathering reactions. Detailed mineralogical analyses of individual samples have identified up to seven arsenic species, the relative proportions of which appear to affect arsenic bioaccessibility. The highest arsenic bioaccessibility (up to 49%) is associated with the presence of calcium-iron arsenate. Samples containing arsenic predominantly as arsenopyrite or scorodite have the lowest bioaccessibility (1%). Other arsenic species identified (predominantly amorphous iron arsenates and arsenic-bearing iron(oxy)hydroxides) are associated with intermediate bioaccessibility (1 to 10%). The presence of a more soluble arsenic phase, even at low concentrations, results in increased arsenic bioaccessibility from the mixed arsenic phases associated with tailings and mine-impacted soils.

The widespread distribution of organoarsenic compounds has been reviewed in terms of the five kingdoms of life. Over 50 organoarsenicals are described. Pathways for their formation are discussed and significant data gaps have been identified.

The distribution and chemical form (speciation) of arsenic in terrestrial food chains determines both the amount of arsenic available to higher organisms, and the toxicity of this metalloid in affected ecosystems. Invertebrates are part of complex terrestrial food webs. This paper provides arsenic concentrations and arsenic speciation profiles for eight orders of terrestrial invertebrates collected at three historical gold mine sites and one background site in Nova Scotia, Canada. Total arsenic concentrations, determined by inductively coupled plasma mass spectrometry (ICP-MS), were dependent upon the classification of invertebrate. Arsenic species were determined by high-performance liquid chromatography (HPLC) ICP-MS and X-ray absorption spectroscopy (XAS). Invertebrates were found by HPLC ICP-MS to contain predominantly arsenite and arsenate in methanol/water extracts, while XAS revealed that most arsenic is bound to sulfur in vivo. Examination of the spatial distribution of arsenic within an ant tissue highlighted the differences between exogenous and endogenous arsenic, as well as the extent to which arsenic is transformed upon ingestion. Similar arsenic speciation patterns for invertebrate groups were observed across sites. Trace amounts of arsenobetaine and arsenocholine were identified in slugs, ants, and spiders.

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.

Models simulating gastric conditions of mammalian (eastern cottontail, Sylvilagus floridanus; short-tailed shrew, Blarina brevicauda) and avian (American robin, Turdus migratorius) receptors were used to investigate the proportion of lead (Pb) mobilized into the digestive juices (the bioaccessible fraction) from soil, earthworms, and vegetation collected at a rifle and pistol (RP) range in eastern Ontario, Canada. Pb concentrations averaged 5044 mg kg(-1) in RP range surface soils, 727 mg kg(-1) in earthworm tissue, and 2945 mg kg(-1) in unwashed vegetation. For mammalian gastric models, the bioaccessible fraction of Pb in soils was 66 +/- 22%, in earthworm tissue was 77 +/- 14%, and in unwashed vegetation was 50 +/- 37%. For the avian gastric model, the bioaccessible fraction of Pb in soil was 53 +/- 43% and in earthworm tissue was 73 +/- 13%. The incorporation of soil and food web intermediate bioaccessibility data into standard risk calculations resulted in predicted risk being reduced for all receptors. The inclusion of bioaccessibility during ecological risk assessment affords a more realistic estimate of contaminant exposure, and is a valuable tool for use in contaminated sites management.

A sequential arsenic extraction method was developed that yielded extraction efficiencies (EE) that were approximately double those using current methods for terrestrial plants. The method was applied to plants from two arsenic contaminated sites and showed potential for risk assessment studies. In the method, plants were extracted first by 1:1 water–methanol followed by 0.1 M hydrochloric (HCl) acid. Total arsenic in plant and soil samples collected from contaminated sites was mineralized by acid digestion and detected by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and hydride generation-atomic absorption spectrometry (HG-AAS). Arsenic speciation was done by high performance liquid chromatography coupled with HG-AAS (HPLC–HGAAS) and by HPLC coupled with ICP-mass spectrometry (HPLC–ICP-MS). Spike recovery experiments with arsenite (As(III)), arsenate (As(V)), methylarsonic acid (MA) and dimethylarsinic acid (DMA) showed stability of the species in the extraction processes. Speciation analysis by X-ray absorption near edge spectroscopy (XANES) demonstrated that no transformation of As(III) and As(V) occurred due to sample handling. Dilute HCl was efficient in extracting arsenic from plants; however, extraction and determination of organic species were difficult in this medium. Sequential extraction with 1:1 water–methanol followed by 0.1 M-HCl was most useful in extracting and speciating both organic and inorganic arsenic from plants. Trace amounts of MA and DMA in plants could be detected by HPLC–HGAAS aided by the process of separation and preconcentration of the sequential extraction method. Both organic and inorganic arsenic compounds could be detected simultaneously in synthetic gastric fluid extracts (GFE) but EEs by this method were lower than those of the sequential method. The developed sequential method was shown to be reliable and applicable to various terrestrial plants for arsenic extraction and speciation.

Traditional Chinese medicines (TCMs) often contain significant levels of potentially toxic elements, including arsenic. Niu Huang Jie Du Pian pills were analyzed to determine the concentration, bioaccessibility (arsenic fraction soluble in the human gastrointestinal system) and chemical form (speciation) of arsenic. Arsenic excretion in urine (including speciation) and facial hair were studied after a one-time ingestion. The pills contained arsenic in the form of realgar, and although the total arsenic that was present in a single pill was high (28 mg), the low bioaccessibility of this form of arsenic predicted that only 4% of it was available for absorption into the bloodstream (1 mg of arsenic per pill). The species of arsenic that were solubilized were inorganic arsenate (As(V)) and arsenite (As(III)) but DMAA and MMAA were detected in urine. Two urinary arsenic excretion peaks were observed: an initial peak several (4-8) hours after ingestion corresponding to the excretion of predominantly As(III), and a larger peak at 14 h corresponding predominantly to DMAA and MMAA. No methylated As(III) species were observed. Facial hair analysis revealed that arsenic concentrations did not increase significantly as a result of the ingestion. Arsenic is incompletely soluble under human gastrointestinal conditions, and is metabolized from the inorganic to organic forms found in urine. Bioaccessible arsenic is comparable to the quantity excreted. Facial hair as a bio-indicator should be further tested.

The bioaccessible concentration and speciation of arsenic (soluble in a gastrointestinal medium and available for absorption into the bloodstream) were determined in softshell clams (Mya arenaria), harvested by local residents until 2005, and in seaweed (Fucus sp.) from an arsenic-contaminated marine site in Seal Harbour, Nova Scotia, Canada. Bioaccessibility extractions to simulate the human gastrointestinal environment (pH 1.5 and glycine for 1h followed by pancreatin, bile extract and pH adjustment to 7 for an additional 4h) and speciation of arsenic in extracts (HPLC-HG-AAS to target inorganic arsenic species) and whole samples (XANES) were carried out. Total arsenic for the clams from the contaminated area ranged from 218 to 228 ppm wet weight, with a bioaccessible fraction of 34-46%, and the major bioaccessible species of arsenic were inorganic. The seaweed from the contaminated area contained 27-43 ppm wet weight total arsenic, with the bioaccessible fraction ranging from 63% to 81%, and inorganic arsenic was also predominant. The predominantly inorganic nature of arsenic in the whole samples was confirmed by XANES. In concurrence with the closure of the area for clam harvesting, the clams and seaweed from Seal Harbour should probably not be used for human consumption.

The surrounding area of Yellowknife, Northwest Territories, Canada, is known for naturally and anthropogenically elevated concentrations of arsenic. Five bird species (gray jay [Perisoreus canadensis], American tree sparrow [Spizella arborea], dark-eyed junco [Junco hyemalis], yellow-rumped warbler [Dendroica coronata], and spruce grouse [Dendragapus canadensis]) were collected from this area. Their tissues were analyzed for total arsenic and for arsenic species, allowing us to report, to our knowledge for the first time, the arsenic characterization in terrestrial birds. Total arsenic concentrations were determined in the terrestrial birds by inductively coupled plasma-optical emission spectrometry, whereas arsenic speciation analysis was performed using high-performance liquid chromatography-inductively coupled plasma-mass spectrometry. Total arsenic concentrations were substantially higher in the terrestrial bird species studied from Yellowknife compared with those reported previously in the literature. The primary arsenic species detected in two of the bird species studied was arsenobetaine. Normally, arsenobetaine is not formed or retained by terrestrial animals. Thus, the birds in the present study were thought to be highly adapted compared with other terrestrial animals, because they were able to form and/or retain this relatively nontoxic arsenic compound. This adaptation is thought to be a consequence of the elevated concentrations of arsenic in the Yellowknife area.

bicoid ( bcd ) RNA localization requires the activity of exuperantia and swallow at sequential steps of oogenesis and is microtubule dependent. In a genetic screen, we identified two novel genes essential for bcd RNA localization. They encode maternal γ-Tubulin37C ( γTub37C ) and γ-tubulin ring complex protein 75 ( Dgrip75 ), both of which are γ-tubulin ring complex components. Mutations in these genes specifically affect bcd RNA localization, whereas other microtubule-dependent processes during oogenesis are not impaired. This provides direct evidence that a subset of microtubules organized by the γ-tubulin ring complex is essential for localization of bcd RNA. At stage 10b, we find γTub37C and Dgrip75 anteriorly concentrated and propose the formation of a microtubule-organizing center at the anterior pole of the oocyte.

Levels of arsenic in water from Meager Creek hot springs, British Columbia, Canada, were found to be naturally elevated. Biota including microbial mats, green algae, sedge, cedar, fleabane, monkey flower, moss, mushrooms and lichens, that were expected to be impacted by the water, were analyzed for total levels of arsenic and for arsenic species. The major arsenic species extracted from all samples were arsenate and arsenite, which are toxic forms of arsenic. Additionally, small amounts of arsenosugars X and XI were detected in microbial mats and green algae, implying that cyanobacteria/bacteria, and possibly green algae are capable of synthesizing arsenosugars from arsenate. Low to trace amounts of arsenosugars X and XI were detected in lichens and the fungus Tarzetta cupularis. A large fraction (on average, greater than 50%) of arsenic was not extracted by using methanol/water (1:1) and the chemical and toxicological significance of this arsenic remains unknown.

The formation of the anterior pattern of the Drosophila embryo is dependent on the localization of the mRNA of the morphogen Bicoid (bcd) to the anterior pole of the egg cell. Staufen protein (STAU) is required in a late step of the localization to anchor the bcd mRNA in the anterior cytoplasm. We have shown previously that endogenous STAU associates specifically with injected bcd mRNA 3'-untranslated region (UTR), resulting in the formation of characteristic RNA-protein particles that are transported along microtubules of the mitotic spindles in a directed manner. The regions recognized by STAU in this in vivo assay are predicted to form three stem-loop structures involving large double-stranded stretches. Here, we show that the STAU interaction requires a double-stranded conformation of the stems within the RNA localization signal. In addition, base pairing between two single-stranded loops plays a major role in particle formation. This loop-loop interaction is intermolecular, not intramolecular; thus dimers or multimers of the RNA localization signal must be associated with STAU in these particles. The bcd mRNA 3' UTR can also dimerize in vitro in the absence of STAU. Thus, in addition to RNA-protein interactions, RNA-RNA interaction might be involved in the formation of ribonucleoprotein particles for transport and localization.

A method, a material system, and the physics for tailoring artificial magnetic field landscapes on micron and submicron length scales over a topographically flat surface in remanence are presented. KeV-He+ ion bombardment induced magnetic patterning was used for the creation of in-plane magnetized domains in Exchange Bias layer systems. This technology sets defined magnetic domain wall charges between the in-plane magnetic domains by individually set domain properties (magnitude and direction of anisotropy parameters) on both sides of the domain wall. The magnetic surface charge distribution was analyzed by magnetic force microscopy and compared to micromagnetic simulations.

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.

Using XANES, we studied the recently identified hexa-coordinated pentavalent arsenic, specifically, octahedral As(V)-glycerol compound As(V)(OCH2CH(O)CH2OH)3. It is stable at all pHs tested (1–12), but is transformed to the conventional tetrahedral AsO43− compound in the presence of water. Dehydration of environmental samples (i.e., Manitoba maple leaf and hare muscle) spiked with a AsO43− standard resulted in XANES features of the As(V)-glycerol compound. Therefore the compound we hypothesize to be the As(V)-glycerol in environmental samples is likely only visible using XAS analysis, and does not appear to survive wet environments such as those in biological systems, where toxicity may be experienced, or in conventional speciation methods, which generally use aqueous separation techniques.

The risk of arsenic exposure to deer mice (Peromyscus maniculatus) living in areas of naturally and anthropogenically elevated arsenic levels was determined using three separate calculations of arsenic daily intake: Estimated daily intake (EDI), bioaccessible EDI (BEDI), and actual daily intake (ADI). The present work is of particular interest, because the risk assessments were determined for animals naturally exposed to arsenic. Gastric fluid extraction was used to obtain bioaccessibility data for soil and plant samples collected from three study sites (background, mine forest, and tailings) in Yellowknife (NT, Canada). Calculations using the EDI indicated that deer mice living in tailings habitat (average soil arsenic concentration, 1,740 +/- 2,240 microg/g) should have been experiencing serious health effects as a result of their exposure to arsenic. Using BEDI and ADI in the risk assessment calculation, however, resulted in an order-of-magnitude decrease in calculated risk. In addition, results calculated using the BEDI and ADI were not significantly different, suggesting that using bioaccessibility provides a more realistic estimate of potential risk. The present results provide evidence that the use of EDI in traditional risk assessments may seriously overestimate the actual risk, which in some instances may result in expensive and unnecessary clean-up measures.

SummarySynaptic connections are stabilized through transsynaptic adhesion complexes that are anchored in the underlying cytoskeleton. The Drosophila neuromuscular junction (NMJs) serves as a model system to unravel genes required for the structural remodeling of synapses. In a mutagenesis screen for regulators of synaptic stability, we recovered mutations in Drosophila ankyrin 2 (ank2) affecting two giant Ank2 isoforms that are specifically expressed in the nervous system and associate with the presynaptic membrane cytoskeleton. ank2 mutant larvae show severe deficits in the stability of NMJs, resulting in a reduction in overall terminal size, withdrawal of synaptic boutons, and disassembly of presynaptic active zones. In addition, lack of Ank2 leads to disintegration of the synaptic microtubule cytoskeleton. Microtubules and microtubule-associated proteins fail to extend into distant boutons. Interestingly, Ank2 functions downstream of spectrin in the anchorage of synaptic microtubules, providing the cytoskeletal scaffold that is essential for synaptic stability.

ICP-MS is very sensitive and has limited matrix effects when used as an element-specific detector for GC in order to identify volatile metal or metalloid species. GC–MS is not very sensitive or selective in the electron ionization (EI) mode, but provides molecular information about volatile species. In this work, an ion trap EI-MS–MS and an ICP-MS system were used as two different detectors for the same GC system to provide complementary information about volatile organometallic species in the complex matrices of landfill and sewage sludge fermentation gases. A simple robust GC separation method with cryotrapping was adequate for the separation of the different metal(loid) containing volatile compounds, and was directly coupled to the ICP-MS system. In addition, gas samples from this GC system were collected in evacuated vials. These fractions were further separated on a capillary column and detected in an ion trap mass spectrometer. For the first time, parent ions, fragmentation patterns, isotopic ratios for Sb and Sn, and MS–MS data were used to identify positively Me3Sb, Me4Sn and Et2Me2Sn in landfill gas and Me3Sb and Me3Bi in fermentation gas.

The filamentous fungus Scopulariopsis brevicaulis produces nonvolatile methylantimony compounds (found in the medium) when grown in antimony(III)-rich medium. To investigate the methyl source, 13CD3-labelled L-methionine was added to the growth medium. After one month sodium borohydride reduction of media samples produced dimethylstibine and trimethylstibine. The methylstibines were separated on a packed GC column and obtained as gaseous fractions. Analysis of the methylstibines, in the gaseous fractions, by CGC–MS (ion-trap) established 13CD3 incorporation in both the trimethyl-and dimethyl-antimony compounds. Copyright © 1999 John Wiley & Sons, Ltd.

Antimony was extracted from environmental biota samples from Yellowknife, NWT and Meager Creek, BC, Canada. Extraction efficiencies ranged from 0.7 to 37% for all samples except for a cattail sample, from which 95% of antimony was extracted. Speciation analysis was carried out by using hydride generation-gas chromatography-atomic absorption spectrometry (HG-GC-AAS). The major antimony species in all samples, including biota extracts and water, was Sb (V). Sb (III) and methylated antimony species were detected in some samples as well. The presence of methylated antimony species in moss from Yellowknife and a water sample from Yellowknife was confirmed by using HG-GC-AAS at a second absorption wavelength, increasing the likelihood that the peaks obtained are due to the presence of antimony compounds. A headspace HG-GC-mass spectrometric (MS) method was developed for the speciation of antimony compounds and this was used to successfully confirm methylantimony species in the headspace following HG of...