This study was undertaken to determine the effectiveness of zero-valent iron (Fe0) and several adsorbent materials in removing uranium (U) from contaminated groundwater and to investigate the rates and mechanisms that are involved in the reactions. Fe0 filings were used as reductants, and the adsorbents included peat materials, iron oxides, and a carbon-based sorbent (Cercona Bone-Char). Results indicate that Fe0 filings are much more effective than the adsorbents in removing uranyl (UO22+) from the aqueous solution. Nearly 100% of U was removed through reactions with Fe0 at an initial concentration up to 76 mM (or 18 000 mg of U/L). Results from the batch adsorption and desorption and from spectroscopic studies indicate that reductive precipitation of U on Fe0 is the major reaction pathway. Only a small percentage (<4%) of UO22+ appeared to be adsorbed on the corrosion products of Fe0 and could be desorbed by leaching with a carbonate solution. The study also showed that the reduced U(IV) species on Fe0 surfaces could be reoxidized and potentially remobilized when the reduced system becomes more oxidized. Results of this research support the application of the permeable reactive barrier technology using Fe0 as a reactive media to intercept U and other groundwater contaminants migrating to the tributaries of Bear Creek at the U.S. Department of Energy's Y-12 Plant located in Oak Ridge, TN.
The present study evaluated a new class of bifunctional anion-exchange resins with improved selectivity and sorption kinetics for removing pertechnetate (TcO4-) from contaminated groundwater. Both laboratory-column and field flow-through experiments were performed, and results indicated that superior performance of the bifunctional resins has been achieved through the use of two quaternary ammonium groups, one having long chains (trihexylamine) for higher selectivity for poorly hydrated large anions and one having shorter chains (triethylamine) for enhanced kinetics and exchange capacity. Field results indicated that the bifunctional resin performed ∼5 times better than one of the best commercial monofunctional anion-exchange resins (e.g., Purolite A-520E) with respect to the removal of TcO4- from contaminated groundwater. Less than 3% of TcO4- breakthrough was observed after ∼700 000 bed volumes (BV) of contaminated groundwater had been treated by the bifunctional resin column (at a flow rate of ∼6 BV/min) at the U.S. Department of Energy's Paducah Gaseous Diffusion Plant site. The results also demonstrate that the new resin is particularly effective in removing low levels of TcO4- (e.g., at nmol/L range), and a cost saving may be realized by using the bifunctional resins for the treatment of large quantities of contaminated groundwater because of its increased selectivity, treatment efficiency, and longevity. The new resin may also be applied for the efficient treatment of other poorly hydrated large anions such as perchlorate (ClO4-) from contaminated groundwater or surface water.
The neurotoxin methylmercury (MeHg) is produced mainly from the transformation of inorganic Hg by microorganisms carrying the hgcAB gene pair. Paddy soils are known to harbor diverse microbial communities exhibiting varying abilities in methylating inorganic Hg, but their distribution and environmental drivers remain unknown at a large spatial scale. Using hgcA gene amplicon sequencing, this study examined Hg-methylating communities from major rice-producing paddy soils across a transect of ∼3600 km and an altitude of ∼1300 m in China. Results showed that hgcA+ OTU richness was higher in tropical and subtropical paddy soils compared to temperate zones. Geobacteraceae, Smithellaceae, and Methanoregulaceae were identified as the dominant hgcA+ families associated with MeHg production, collectively accounting for up to 77% of total hgcA+ sequences. Hierarchical partitioning analyses revealed that pH was the main driver of hgcA genes from Geobacteraceae (14.8%) and Methanoregulaceae (16.3%), while altitude accounted for 21.4% of hgcA genes from Smithellaceae. Based on these environmental preferences, a machine-learning algorithm was used to predict the spatial distribution of these dominant hgcA+ families, thereby providing novel insights into important microbial determinants for improved prediction of MeHg production in paddy soils across China.
Microplastics (MPs) as emerging contaminants have accumulated extensively in agricultural ecosystems and are known to exert important effects on biogeochemical processes. However, how MPs in paddy soils influence the conversion of mercury (Hg) to neurotoxic methylmercury (MeHg) remains poorly understood. Here, we evaluated effects of MPs on Hg methylation and associated microbial communities in microcosms using two typical paddy soils in China (i.e., yellow and red soils). Results showed that the MPs significantly increased MeHg production but the extent differed between the two soils. The plastisphere of both soils exhibited higher Hg methylation potential than the bulk soil, which is an important reason for the observed increases of soil MeHg in the MP treatment. Significant divergences in the community composition of Hg methylators were observed between the plastisphere and the bulk soil. The plastisphere had higher proportions of Geobacterales in the yellow soil and Methanomicrobia in the red soil compared with the respective bulk soil. In addition, soil plastisphere had more densely connected microbial groups between non-Hg methylators and Hg methylators than the bulk soil. These findings suggest plastisphere as a unique biotope for MeHg production and provide new insights into the environment risks of MP accumulation in agricultural soils.
This chapter contains sections titled: Introduction The relationship between glucosidase inhibition and antiviral action Fate of viral glycoproteins in glucosidase-inhibited cells Specificity of glucosidase inhibition N-Alkyl DNJs inhibit virus growth by non-glucosidase inhibitory mechanisms – other potential activities of these compounds New directions for improving glucosidase inhibitors as antiviral agents References
Earth and Space Science Open Archive This preprint has been submitted to and is under consideration at Journal of Geophysical Research - Biogeosciences. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.Learn more about preprints preprintOpen AccessYou are viewing the latest version by default [v2]Simulated hydrological dynamics and coupled iron redox cycling impact methane production in an Arctic soilAuthorsBenjamin NSulmanFengmingYuanTeriO'MearaBaohuaGuElizabeth M.HerndoniDJianqiuZhengPeter E.ThorntoniDDavid EGrahamiDSee all authors Benjamin N SulmanCorresponding Author• Submitting AuthorOak Ridge National Laboratoryview email addressThe email was not providedcopy email addressFengming YuanOak Ridge National Laboratoryview email addressThe email was not providedcopy email addressTeri O'MearaSmithsonian Environmental Research Centerview email addressThe email was not providedcopy email addressBaohua GuOak Ridge National Laboratory (DOE)view email addressThe email was not providedcopy email addressElizabeth M. HerndoniDKent State UniversityiDhttps://orcid.org/0000-0002-9194-5493view email addressThe email was not providedcopy email addressJianqiu ZhengPacific Northwest National Laboratoryview email addressThe email was not providedcopy email addressPeter E. ThorntoniDOak Ridge National Laboratory (DOE)iDhttps://orcid.org/0000-0002-4759-5158view email addressThe email was not providedcopy email addressDavid E GrahamiDOak Ridge National Laboratory (DOE)iDhttps://orcid.org/0000-0001-8968-7344view email addressThe email was not providedcopy email address
Treatment of perchlorate-contaminated water using highly selective, regenerable ion-exchange and perchlorate-destruction technologies was demonstrated at a field site in California. Four treatment and four regeneration cycles were carried out, and no significant deterioration of resin performance was noted in 2 years. The bifunctional resin (Purolite A-530E) treated about 37 000 empty bed volumes (BVs) of groundwater before a significant breakthrough of perchlorate occurred at an average flow rate of 150 gpm (or 1 BV/min) and a feed perchlorate concentration of about 860 μg/L. Sorbed perchlorate (∼20 kg) was quantitatively recovered by eluting with as little as 1 BV of the FeCl3−HCl regenerant solution. The eluted ClO4- was highly concentrated in the third quarter of the first BV of the regenerant solution with a concentration up to 100 000 mg/L. This concentrated effluent greatly facilitated subsequent perchlorate destruction or recovery by precipitation as KClO4 salts. High perchlorate destruction efficiency (92−97%) was observed by reduction with FeCl2 in a thermoreactor, which enabled recycling of the FeCl3−HCl regenerant solution, thereby minimizing the need to dispose of secondary wastes containing ClO4-. This study demonstrates that a combination of novel selective, regenerable ion-exchange and perchlorate-destruction and/or recovery technologies could potentially lead to enhanced treatment efficiency and minimized secondary waste production.
ABSTRACT The high levels of hepatitis B virus (HBV) surface antigen (HBsAg)-bearing subviral particles in the serum of chronically infected individuals are thought to play a role in suppressing the HBV-specific immune response. Current therapeutics are not directed at reducing this viral antigenemia; thus, our group has focused on identifying inhibitors of HBsAg secretion. By using the HBV-expressing cell line HepG2.2.15, high-throughput screening of an 80,288-compound synthetic small-molecule library identified HBF-0259, an aromatically substituted tetrahydro-tetrazolo-(1, 5- a )-pyrimidine. Following resynthesis, HBF-0259 had a 50% effective concentration of approximately 1.5 μM in a secondary, HBV-expressing cell line, with a concentration that exhibited 50% cytotoxicity of >50 μM. The equilibrium concentration of HBF-0259 in aqueous solution at physiological pH was 15 to 16 μM; the selective index was thus >9. As intended by our screening paradigm, HBF-0259 is a selective, potent inhibitor of secretion of both subviral and DNA-containing viral particles, while the secretion of α-1-acid glycoprotein and α-1-antitrypsin was unaffected. The HBV e antigen, which is not a constituent of HBV particles, was also unaffected, suggesting that the secretion of particles bearing HBV structural glycoproteins is targeted directly. Inhibitory activity was also confirmed by transfection of HBsAg, indicating that the action of the compound is independent of those of other viral proteins. HBF-0259 had no effect on HBV DNA synthesis, demonstrating that inhibition is independent of viral genomic replication. Finally, HBF-0259 had little or no effect on the cell-to-cell spread of two unrelated viruses, suggesting that it is a specific inhibitor of secretion of HBsAg. Possible mechanisms of action and the implications for its development are discussed.
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