Control of mercury and methylmercury in contaminated sediments using biochars: A long-term microcosm study

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.apgeochem.2018.02.004 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/The effectiveness of activated carbon and four types of biochar, switchgrass (300 °C and 600 °C), poultry manure (600 °C), and oak (∼700 °C) with respect to mercury (Hg) and methylmercury (MeHg) control was assessed in microcosm experiments carried out for 524 d. Early in the study (<30 d), minimal differences in concentrations of <0.45-μm filtered total Hg (THg) in control and 5% biochar-amended systems were observed. At later stages, THg concentrations in the amended systems decreased to 8–80% of concentrations in the sediment controls. Aqueous concentrations of MeHg were generally lower in the amended systems than in the controls, with an initial peak in MeHg concentration corresponding to the onset of iron and sulfate reduction (∼40 d) and a second peak to methanogenic conditions (∼400 d). Pyrosequencing analyses indicate the microbial communities initially associated with fermenters and later shifted to iron-reducing bacteria (FeRB), sulfate-reducing bacteria (SRB), and methanogens. These analyses also indicate the existence of 12 organisms associated with Hg methylation in all systems. Community shifts were correlated with changes in the concentrations of carbon sources (dissolved organic carbon (DOC) and organic acids) and electron acceptors (NO3−, Fe, and SO42−). Co-blending of biochars with Hg-contaminated sediment can be an alternative remediation method for controlling the release of Hg and MeHg, but the potential for Hg methylation under some conditions requires consideration.Natural Sciences and Engineering Research Council of CanadaCanada Research ChairsE. I. du Pont de Nemours and Compan

Microbial processes with the potential to mobilize As from a circumneutral-pH mixture of flotation and roaster tailings

The Northwest Tailings Containment Area at the inactive Giant Mine (Canada) contains a complex mixture of arsenic-containing substances, including flotation tailings (84.8 wt%; with 0.4 wt% residual S), roaster calcine wastes (14.4 wt% Fe oxides), and arsenic trioxide (0.8 wt%) derived from an electrostatic precipitator as well as As-containing water (21.3 ± 4.1 mg L−1 As) derived from the underground mine workings. In the vadose zone the tailings pore water has a pH of 7.6 and contains elevated metal(loid)s (2.37 ± 5.90 mg L−1 As); mineral oxidizers account for 2.5% of total 16S rRNA reads in solid samples. In the underlying saturated tailings, dissolved Fe and As concentrations increase with depth (up to 72 and 20 mg L−1, respectively), and the mean relative abundance of Fe(III)-reducers is 0.54% of total reads. The potential for As mobilization via both reductive and oxidative (bio)processes should be considered in Giant Mine remediation activities. The current remediation plan includes installation of an engineered cover that incorporates a geosynthetic barrier layer

Warm-up phenomenon in myotonia associated with the V445M sodium channel mutation

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Removal of arsenic and metals from groundwater impacted by mine waste using zero-valent iron and organic carbon:Laboratory column experiments

Acid mine drainage and the associated contaminants, including As and metals, are ongoing environmental issues. Passive remediation technologies have the potential to remove As from mine waste effluents. A series of laboratory column experiments was conducted to evaluate the effectiveness of varying mixtures of organic carbon (OC), zero-valent iron (ZVI), and limestone for the treatment of As, metals, SO42− , and acidity in groundwater from an abandoned gold mine. The onset of bacterially-mediated SO42− reduction was indicated by a decrease in Eh, a decline in aqueous SO42− concentrations coupled with enrichment of δ34S, and the presence of sulfatereducing bacteria and H2S. Removal of As was observed within the first 3 cm of reactive material, to values below 10 µg L− 1, representing &gt; 99.9% removal. An increase in pH from 3.5 to circumneutral values and removal of metals including Al, Cu, and Zn was also observed. Synchrotron results suggest As was removed through precipitation of As-crystalline phases such as realgar and orpiment, or through adsorption as As(V) on ferrihydrite. The results indicate the potential for a mixture of OC and ZVI to remove As from acidic, mine-impacted water