Microbiological characteristics in a zero-valent iron reactive barrier

Zero-valent iron (Fe0)-based permeable reactive barriertreatment has been generating great interest for passivegroundwater remediation, yet few studies have paid particularattention to the microbial activity and characteristics withinand in the vicinity of the Fe0-barrier matrix. The presentstudy was undertaken to evaluate the microbial population andcommunity composition in the reducing zone of influence byFe0 corrosion in the barrier at the Oak Ridge Y-12 Plantsite. Both phospholipid fatty acids and DNA analyses were usedto determine the total microbial population and microbialfunctional groups, including sulfate-reducing bacteria,denitrifying bacteria, and methanogens, in groundwater andsoil/iron core samples. A diverse microbial community wasidentified in the strongly reducing Fe0 environment despitea relatively high pH condition within the Fe0 barrier (up topH 10). In comparison with those found in the backgroundsoil/groundwater samples, the enhanced microbial populationranged from 1 to 3 orders of magnitude and appeared to increase from upgradient of the barrier to downgradient soil. Inaddition, microbial community composition appeared to change overtime, and the bacterial types of microorganismsincreased consistently as the barrier aged. DNA analysisindicated the presence of sulfate-reducing and denitrifyingbacteria in the barrier and its surrounding soil. However, theactivity of methanogens was found to be relatively low,presumably as a result of the competition by sulfate/metal-reducing bacteria and denitrifying bacteria because of the unlimited availability of sulfate and nitrate in the site groundwater. Results of this study provide evidenceof a diverse microbial population within and in the vicinity ofthe iron barrier, although the important roles of microbial activity, either beneficially or detrimentally, on the longevityand enduring efficiency of the Fe0 barriers are yet to be evaluated.

Comparative performances of birnessite and cryptomelane MnO as electrode material in neutral aqueous lithium salt for supercapacitor application

Na-doped Birnessite-type manganese oxide (d-MnO) has been synthesized using the chemical method and characterized through X-ray diffraction and SEM, showing the lamellar structure and high crystal structure. A comparative study of the electrochemical performances of this material with those of the commercial Cryptomelane-type MnO has then been undertaken in ten neutral aqueous electrolytes for supercapacitor applications. Aqueous electrolytes, containing a lithium salt, LiX (where X = SO , NO, CHCO , CHSO, ClO , CHCO, TFSI, Beti, BOB, or Lact), have been first prepared under neutral pH conditions to reach the salt concentration, providing the maximum in conductivity. Their transport properties are then investigated through conductivities, viscosities, and self-diffusion coefficient measurements. Second, the thermal behaviors of these electrolytic aqueous solutions are then evaluated by using a differential scanning calorimeter from (213.15 to 473.15) K in order to access their liquid range temperatures. Cyclic voltammograms (CV) in three electrode configurations are thereafter investigated using Na Birnessite and Cryptomelane as working electrode material from (-0.05 to 1.5) V versus Ag/AgCl at various sweep rates from (2 to 100) mV·s. According to anion nature/structure and manganese oxide material type, different CV responses are observed, presenting a pure capacitive profile for Beti or CH CO and an additional pseudocapacitive signal for the smallest anions, such as ClO and NO . The capacitances, energies, and efficiencies are finally calculated. These results indicate clearly that electrolytes based on a mineral lithium salt under neutral pH condition and high salt concentration (up to 5 mol·L) have better electrochemical performances than organic ones, up to 1.4 V with good material stability and capacity retention. The relationship between transport properties, electrostatic and steric hindrance considerations of hydrated ions, and their electrochemical performances is discussed in order to understand further the lithium intercalation-deintercalation processes in the lamellar or tunnel structure of investigated MnO. © 2013 American Chemical Society.

Condition Assessment and Preservation of Open-Air Rock Art Panels During Climate Change

Thousands of Neolithic and Bronze Age open-air rock art panels exist across the countryside in northern England. However, desecration, pollution, and other factors are threatening the survival of these iconic stone monuments. Evidence suggest that rates of panel deterioration may be increasing, although it is not clear whether this is due to local factors or wider environmental influences accelerated by environmental change. To examine this question, 18 rock art panels with varied art motifs were studied at two major panel locations at Lordenshaw and Weetwood Moor in Northumberland. A condition assessment
tool was used to first quantify the level of deterioration of each panel (called “staging”). Stage estimates then were compared statistically with 27 geochemical and physical descriptors of local environments, such as soil moisture, salinity, pH, lichen coverage, soil anions and cation levels, and panel orientation, slope, and standing height. In parallel, climate modelling was performed using UKCP09 to assess how projected climatic conditions (to 2099) might affect the environmental descriptors most correlated with elevated stone deterioration. Only two descriptors significantly correlated (P < 0.05) with increased stage: the standing height of the panel and the exchangeable cation content of the local soils, although moisture conditions also were potentially influential at some panels. Climate modelling predicts warming temperatures, more seasonally variable precipitation, and increased wind speeds, which hint stone deterioration could accelerate in the future due to increased physiochemical weathering. We recommend key panels be targeted for immediate management intervention, focusing on reducing wind exposures, improving site drainage, and potentially immobilizing soil salts.

Soft matter pH sensing: from luminescent lanthanide pH switches in solution to sensing in hydrogels

The synthesis, complexation, and photophysical properties of the Eu(III)-based quinoline cyclen conjugate complex Eu1 and its permanent, noncovalent incorporation into hydrogels as sensitive, interference-free pH sensing materials for biological media are described. The Eu(III) emission in both solution and hydrogel media was switched reversibly on-off as a function of pH with a large, greater than order of magnitude enhancement in Eu(III) emission. The irreversible incorporation of Eu1 into water-permeable hydrogels was achieved using poly[methyl methacrylate-co-2-hydroxyethyl methacrylate]- based hydrogels, and the luminescent properties of the novel sensor materials, using confocal laser- scanning microscopy and steady state luminescence, were characterized and demonstrated to be retained with respect to solution behavior. Water uptake and dehydration behavior of the sensor-incorporated materials was also characterized and shown to be dependent on the material composition.

Pilot-scale evaluation of the application of low pH-inducible polyphosphate accumulation to the biological removal of phosphate from wastewaters.

To investigate the possible biotechnological application of the phenomenon of low pH-inducible phosphate uptake and polyphosphate accumulation, previously reported using pure microbial cultures and under laboratory conditions, a 2000 L activated sludge pilot plant was constructed at a municipal sewage treatment works. When operated as a single-stage reactor this removed more than 60% of influent phosphate from primary settled sewage at a pH of 6.0, as opposed to approximately 30% at the typical operational pH for the works of 7.0-7.3-yet without any deleterious effect on other treatment parameters. At these pH values the phosphorus content of the sludge was, respectively, 4.2% and 2.0%. At pH 6.0 some 33.9% of sludge microbial cells were observed to contain polyphosphate inclusions; the corresponding value at pH 7.0 was 18.7%. Such a process may serve as a prototype for the development of alternative biological and chemical options for phosphate removal from wastewaters.