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 Xray absorption near-edge structure analysis shows arsenic in these near-surface samples is mainly in 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 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.3

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Understanding the solid-phase speciation of arsenic in soils and sediments is important in evaluations of the potential mobility of arsenic and of its bio-availability in the environment. This is especially true in mine-infl uenced environments, where arsenic commonly is present at concentrations two and three orders of magnitude above quality criteria for soils and sediments. Arsenicbearing particulates dispersed through hydraulic transport or aerosol emissions can represent a persistent source of contamination in sediments and soils adjacent to past mining and metallurgical operations. The stability and mobility of arsenic associated with these phases depend on the chemical form and oxidation state of the arsenic and the interaction with post-depositional geochemical conditions. The Giant mine in Yellowknife, Northwest Territories, roasted arsenic-bearing gold ore from 1949 to 1999. The roasting process decomposed arsenic-bearing sulfi des (pyrite and arsenopyrite) to produce a calcine containing fi ne (generally <50 m) arsenic-bearing iron oxides. We have applied synchrotron As K-edge micro X-ray Absorption Near-Edge Structure (XANES) and XRD as part of a grain-by-grain mineralogical approach for the direct determination of the host mineralogy and oxidation state of As in these roaster-derived iron oxides. The grain-scale approach has resolved potential ambiguities that would have existed had only bulk XANES and XRD methods been applied. Using combined optical microscopy, electron microprobe and XRD, we have determined that the roaster-iron oxides are nanocrystalline grains of maghemite containing <0.5 to 7 wt.% As. Some of these arsenic-bearing nanocrystalline grains are a mixture of maghemite and hematite. All roaster iron oxides, including those present in 50-year-old tailings, contain mixtures of As 5+ and As 3+ . The persistence of As 3+ in roaster-derived maghemite in shallow subareal (oxidized) shoreline tailings for over 50 years suggests that the arsenic is relatively stable under these conditions, even though As 3+ is a reduced form of arsenic, and maghemite is normally considered a metastable phase.

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BackgroundArsenic is toxic to most living cells. The two soluble inorganic forms of arsenic are arsenite (+3) and arsenate (+5), with arsenite the more toxic. Prokaryotic metabolism of arsenic has been reported in both thermal and moderate environments and has been shown to be involved in the redox cycling of arsenic. No arsenic metabolism (either dissimilatory arsenate reduction or arsenite oxidation) has ever been reported in cold environments (i.e. < 10°C).ResultsOur study site is located 512 kilometres south of the Arctic Circle in the Northwest Territories, Canada in an inactive gold mine which contains mine waste water in excess of 50 mM arsenic. Several thousand tonnes of arsenic trioxide dust are stored in underground chambers and microbial biofilms grow on the chamber walls below seepage points rich in arsenite-containing solutions. We compared the arsenite oxidisers in two subsamples (which differed in arsenite concentration) collected from one biofilm. 'Species' (sequence) richness did not differ between subsamples, but the relative importance of the three identifiable clades did. An arsenite-oxidising bacterium (designated GM1) was isolated, and was shown to oxidise arsenite in the early exponential growth phase and to grow at a broad range of temperatures (4-25°C). Its arsenite oxidase was constitutively expressed and functioned over a broad temperature range.ConclusionsThe diversity of arsenite oxidisers does not significantly differ from two subsamples of a microbial biofilm that vary in arsenite concentrations. GM1 is the first psychrotolerant arsenite oxidiser to be isolated with the ability to grow below 10°C. This ability to grow at low temperatures could be harnessed for arsenic bioremediation in moderate to cold climates.

Determination of the source and form of metals in house dust is important to those working to understand human and particularly childhood exposure to metals in residential environments. We report the development of a synchrotron microprobe technique for characterization of multiple metal hosts in house dust. We have applied X-ray fluorescence for chemical characterization and X-ray diffraction for crystal structure identification using microfocused synchrotron X-rays at a less than 10 μm spot size. The technique has been evaluated by application to archived house dust samples containing elevated concentrations of Pb, Zn, and Ba in bedroom dust, and Pb and As in living room dust. The technique was also applied to a sample of soil from the corresponding garden to identify linkages between indoor and outdoor sources of metals. Paint pigments including white lead (hydrocerussite) and lithopone (wurtzite and barite) are the primary source of Pb, Zn, and Ba in bedroom dust, probably related to renovation activity in the home at the time of sampling. The much lower Pb content in the living room dust shows a relationship to the exterior soil and no specific evidence of Pb and Zn from the bedroom paint pigments. The technique was also successful at confirming the presence of chromated copper arsenate treated wood as a source of As in the living room dust. The results of the study have confirmed the utility of this approach in identifying specific metal forms within the dust.

A review discussing the isolation and bioactivity of tryptophan-linked cyclic peptide natural products, along with discussion of their total synthesis and biosynthesis.

Savolitinib (AZD6094, HMPL-504, volitinib) is an oral, bioavailable, selective MET-tyrosine kinase inhibitor. This randomized, double-blind, 3-way, crossover phase 1 study of savolitinib versus moxifloxacin (positive control) and placeboevaluated effects on the QT interval after a single savolitinib dose. Healthy non-Japanese men were randomized to 1 of 6 treatment sequences, receiving single doses of savolitinib 600 mg, moxifloxacin 400 mg, and placebo. The primary end point was time-matched, placebo-adjusted change from baseline in the QT interval corrected for the time between corresponding points on 2 consecutive R waves on electrocardiogram (RR) by the Fridericia formula ( QTcF). Secondary end points included 12-lead electrocardiogram (ECG) variables, pharmacokinetics, and safety. All 3 treatment periods were completed by 44 of 45 participants (98%). Baseline demographics were balanced across treatment groups. After a single savolitinib 600-mg dose, the highest least-squares mean QTcF of 12 milliseconds was observed 5 hours postdose. Upper limits of the 2-sided 90% confidence interval for QTcF exceeded 10 milliseconds (the prespecified International Council for Harmonisation limit) 3-6 hours postsavolitinib but otherwise remained less than the threshold. Savolitinib showed no additional effect on PR, QRS, QT, or RR intervals. A positive QTcF signal from the moxifloxacin group confirmed study validity. Savolitinib was well tolerated, with a low incidence of adverse events. In this thorough QT/QTc study, QTcF prolongation was observed with a single savolitinib 600-mg dose. ECG monitoring will be implemented in ongoing and future studies of savolitinib to assess the clinical relevance of the observed QT changes from this study.