scholarly journals Bioremediation of Uranium- and Nitrate-Contaminated Groundwater after the In Situ Leach Mining of Uranium

Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3188
Author(s):  
Rehemanjiang Wufuer ◽  
Jia Duo ◽  
Wenfeng Li ◽  
Jinglong Fan ◽  
Xiangliang Pan
Keyword(s):  
Nitrate Reduction ◽  
Bacterial Species ◽  
Contaminated Groundwater ◽  
Noticeable Effect ◽  
Initial Concentration ◽  
Groundwater Samples ◽  
Ferric Oxides ◽  
Neutral Conditions ◽  
Scanning Electron

Uranium and nitrate are common groundwater pollutants near in situ leach uranium mines. However, we still lack techniques that can simultaneously immobilize uranium and reduce nitrate using a single bacterial species. In this study, the potential of simultaneous uranium immobilization and nitrate reduction by a single AFODN (anaerobic Fe(II) oxidizing denitrifier), Clostridium sp. PXL2, was investigated. Clostridium sp. PXL2 showed tolerance to U(VI) concentrations varying from 4.2 µM to 42 µM. The U(VI) immobilization and nitrate reduction rates in groundwater samples inoculated with this bacterium reached up to 75.1% and 55.7%, respectively, under neutral conditions. Exposure to oxidation conditions led to further U(VI) removal but did not show any noticeable effect on nitrate reduction. The U(VI) immobilization rate reached up to 85% with an increased Fe(II) initial concentration, but this inhibited nitrate reduction. SEM (scanning electron microscopy) coupled with EDS (energy dispersive spectroscopy) showed that the U(VI) immobilization was mainly due to sorption to amorphous ferric oxides. U(VI) and nitrate bioremediation by AFODNs, including Clostridium sp. PXL2, may provide a promising method for the treatment of uranium- and nitrate-contaminated groundwater after the in situ leach mining of uranium.

scholarly journals Molybdenum Availability Is Key to Nitrate Removal in Contaminated Groundwater Environments

2015 ◽  
Vol 81 (15) ◽  
pp. 4976-4983 ◽  
Author(s):  
Michael P. Thorgersen ◽  
W. Andrew Lancaster ◽  
Brian J. Vaccaro ◽  
Farris L. Poole ◽  
Andrea M. Rocha ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Nitrate Removal ◽  
Pseudomonas Stutzeri ◽  
Contaminated Groundwater ◽  
Content Type ◽  
Oak Ridge ◽  
Groundwater Samples ◽  
Almost All ◽  
Toxic Concentrations ◽  
Global Nitrogen Cycle

ABSTRACTThe concentrations of molybdenum (Mo) and 25 other metals were measured in groundwater samples from 80 wells on the Oak Ridge Reservation (ORR) (Oak Ridge, TN), many of which are contaminated with nitrate, as well as uranium and various other metals. The concentrations of nitrate and uranium were in the ranges of 0.1 μM to 230 mM and <0.2 nM to 580 μM, respectively. Almost all metals examined had significantly greater median concentrations in a subset of wells that were highly contaminated with uranium (≥126 nM). They included cadmium, manganese, and cobalt, which were 1,300- to 2,700-fold higher. A notable exception, however, was Mo, which had a lower median concentration in the uranium-contaminated wells. This is significant, because Mo is essential in the dissimilatory nitrate reduction branch of the global nitrogen cycle. It is required at the catalytic site of nitrate reductase, the enzyme that reduces nitrate to nitrite. Moreover, more than 85% of the groundwater samples contained less than 10 nM Mo, whereas concentrations of 10 to 100 nM Mo were required for efficient growth by nitrate reduction for twoPseudomonasstrains isolated from ORR wells and by a model denitrifier,Pseudomonas stutzeriRCH2. Higher concentrations of Mo tended to inhibit the growth of these strains due to the accumulation of toxic concentrations of nitrite, and this effect was exacerbated at high nitrate concentrations. The relevance of these results to a Mo-based nitrate removal strategy and the potential community-driving role that Mo plays in contaminated environments are discussed.

Feasibility Study of In-Situ Bioremediation of Atrazine by Pseudomonas SP. ADP (PADP) in a Laboratory Scale Model Aquifer

2007 ◽  
Vol 7 ◽  
pp. 105 ◽  
Author(s):  
Binita K. Shrestha ◽  
Pawan Raj Shakya ◽  
M. I. M. Soares
Keyword(s):  
Dissolved Oxygen ◽  
Water Flow ◽  
Nitrate Reduction ◽  
Total Dissolved Solids ◽  
Scale Model ◽  
Contaminated Groundwater ◽  
Pseudomonas Sp ◽  
Dissolved Solids ◽  
Reactive Barrier

The feasibility of in-situ bioremediation of atrazine-contaminated groundwater by Pseudomonas sp. ADP (PADP) was tested in a two-dimensional laboratory scale model aquifer. The experimental set-up consisted of three compartments: an inlet chamber, a saturated sandy aquifer with a biological permeable reactive barrier (BPRB) and an outlet chamber. Multi-layer samplers (MLSs) at 10, 25 and 40 cm from the bed base were located at 7, 28.5 (well), 42.5 (BPRB) and 55 cm from the inlet. Artificial atrazine-contaminated groundwater (1 mg/L) amended with nitrate (20 mg/L NO3- -N) flowed horizontally through the aquifer at a rate of 5.5 cm/day. Inoculation of the reactive barrier was achieved by temporarily stopping the water flow, and injecting into the reactive barrier 1 L of a PADP suspension with a concentration of 5.6 x 109 CFU/mL; water flow was resumed one hour later. To enhance bacterial activity, a citrate solution (1 g/L) was injected into the barrier twice a week. During the four months of operation, water samples were withdrawn weekly from the MLSs at each sampling station and from the inlet and the outlet, to determine the following water quality parameters: dissolved oxygen, pH, temperature, nitrate, atrazine, total dissolved solids and bacterial colony counts (CFU). The concentration of atrazine was practically unchanged from the inlet to the barrier, and an average removal of 50% was observed at the barrier. This removal in the concentration of atrazine was maintained downstream with a slight increase at the outlet, probably due to matrix heterogeneities and preferential channeling. The concentration of dissolved oxygen also decreased along the water path and the lowest value, 2.2 mg/L, was measured at the barrier and at the station downstream. A very small decline was detected in pH values, which decreased from an average of 8.4 ± 0.1 at the inlet to an average of 8.0 ± 0.1 at the outlet. The values of total dissolved solids and temperature did not change significantly throughout the aquifer. In general, low levels of nitrate reduction were detected, although up to 80% reduction was observed at the third week at location 55 cm, with no detectable decrease in the concentration of dissolved oxygen. No correlation was found between degradation of atrazine and nitrate reduction. Our results indicate that in-situ treatment may be a suitable method for the restoration of atrazine contaminated aquifers. <i> Nepal Journal of Science and Technology</i> Vol. 7, 2006

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

High-Resolution Resistance Mapping in SEM

2018 ◽  
Author(s):  
Grigore Moldovan ◽  
Wolfgang Joachimi ◽  
Guillaume Boetsch ◽  
Jörg Jatzkowski ◽  
Frank Altman
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Reference Structure ◽  
Total Resistance ◽  
Embedded Electronics ◽  
Improved Performance ◽  
Mapping Techniques ◽  
Scanning Electron

Abstract This work presents advanced resistance mapping techniques based on Scanning Electron Microscopy (SEM) with nanoprobing systems and the related embedded electronics. Focus is placed on recent advances to reduce noise and increase speed, such as integration of dedicated in situ electronics into the nanoprobing platform, as well as an important transition from current-sensitive to voltagesensitive amplification. We show that it is now possible to record resistance maps with a resistance sensitivity in the 10W range, even when the total resistance of the mapped structures is in the range of 100W. A reference structure is used to illustrate the improved performance, and a lowresistance failure case is presented as an example of analysis made possible by these developments.

On-site and in situ bioremediation of wood-preservative contaminated groundwater

2000 ◽  
Vol 42 (5-6) ◽  
pp. 371-376 ◽  
Author(s):  
J.A. Puhakka ◽  
K.T. Järvinen ◽  
J.H. Langwaldt ◽  
E.S. Melin ◽  
M.K. Männistö ◽  
...  
Keyword(s):  
Iron Oxidation ◽  
Wood Preservative ◽  
Pilot Scale ◽  
High Rate ◽  
Contaminated Groundwater ◽  
Groundwater Temperature ◽  
In Situ Bioremediation ◽  
Contaminated Aquifer ◽  
Fluidized Bed Process

This paper reviews ten years of research on on-site and in situ bioremediation of chlorophenol contaminated groundwater. Laboratory experiments on the development of a high-rate, fluidized-bed process resulted in a full-scale, pump-and-treat application which has operated for several years. The system operates at ambient groundwater temperature of 7 to 9°C at 2.7 d hydraulic retention time and chlorophenol removal efficiencies of 98.5 to 99.9%. The microbial ecology studies of the contaminated aquifer revealed a diverse chlorophenol-degrading community. In situ biodegradation of chlorophenols is controlled by oxygen availability, only. Laboratory and pilot-scale experiments showed the potential for in situ aquifer bioremediation with iron oxidation and precipitation as a potential problem.

scholarly journals Design and Characterization of Microscale Auxetic and Anisotropic Structures Fabricated by Multiphoton Lithography

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 446
Author(s):  
Ioannis Spanos ◽  
Zacharias Vangelatos ◽  
Costas Grigoropoulos ◽  
Maria Farsari
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Mechanical Performance ◽  
Element Analysis ◽  
Mechanical Responses ◽  
Multiphoton Lithography ◽  
Anisotropic Structures ◽  
Scanning Electron

The need for control of the elastic properties of architected materials has been accentuated due to the advances in modelling and characterization. Among the plethora of unconventional mechanical responses, controlled anisotropy and auxeticity have been promulgated as a new avenue in bioengineering applications. This paper aims to delineate the mechanical performance of characteristic auxetic and anisotropic designs fabricated by multiphoton lithography. Through finite element analysis the distinct responses of representative topologies are conveyed. In addition, nanoindentation experiments observed in-situ through scanning electron microscopy enable the validation of the modeling and the observation of the anisotropic or auxetic phenomena. Our results herald how these categories of architected materials can be investigated at the microscale.

scholarly journals Formation of Bushveld anorthosite by reactive porous flow

2020 ◽  
Vol 176 (1) ◽  
Author(s):  
W. D. Maier ◽  
S.-J. Barnes ◽  
D. Muir ◽  
D. Savard ◽  
Y. Lahaye ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Compositional Data ◽  
Crystal Mush ◽  
Porous Flow ◽  
Scanning Electron

AbstractBushveld anorthosites commonly contain the so-called “mottles” comprising irregular, typically centimetric domains of oikocrystic pyroxene or olivine enclosing small, embayed plagioclase grains. The mottles were traditionally interpreted to result from solidification of trapped intercumulus liquid or via in situ crystallisation at the top of the crystal mush. Here, we present microtextural and compositional data of a mottle to place further constraints on the formation of anorthosite layers. Element maps generated by scanning electron microscopy reveal that plagioclase within and around the mottle has markedly elevated An contents (up to An95) relative to the host anorthosite and is strongly reversely zoned. Other unusual features, some of which were reported previously, include a halo of sub-vertically oriented, acicular phlogopite around the mottle, elevated contents of disseminated sulfides, and relatively evolved yet Ni-rich olivine (Fo71–75, 3000 ppm Ni). These features are interpreted to result from reactive porous flow of hot, acidic fluid enriched in nickel and sulfur through proto norite. The fluids dissolved mafic minerals and leached alkalis from the outer rims of plagioclase grains. Reconnaissance studies suggest that reversed zoning of plagioclase is a common feature in Bushveld norite and anorthosite. This implies that reactive porous flow could have been far more pervasive than currently realised and that Bushveld anorthosite layers formed through recrystallisation of norites.

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