scholarly journals Spatial Distribution of PCB Dechlorinating Bacteria and Activities in Contaminated Soil

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Birthe V. Kjellerup ◽  
Piuly Paul ◽  
Upal Ghosh ◽  
Harold D. May ◽  
Kevin R. Sowers
Keyword(s):  
Soil Aggregates ◽  
Soil Samples ◽  
Time Analysis ◽  
Baltimore Harbor ◽  
Rate Limiting Step ◽  
Dechlorinating Bacteria ◽  
Pcb Dechlorination ◽  
Rate Limiting ◽  
Aerobic And Anaerobic

Soil samples contaminated with Aroclor 1260 were analyzed for microbial PCB dechlorination potential, which is the rate-limiting step for complete PCB degradation. The average chlorines per biphenyl varied throughout the site suggesting that different rates ofin situdechlorination had occurred over time. Analysis of PCB transforming (aerobic and anaerobic) microbial communities and dechlorinating potential revealed spatial heterogeneity of both putative PCB transforming phylotypes and dechlorination activity. Some soil samples inhibited PCB dechlorination in active sediment from Baltimore Harbor indicating that metal or organic cocontaminants might cause the observed heterogeneity ofin situdechlorination. Bioaugmentation of soil samples contaminated with PCBs ranging from 4.6 to 265 ppm with a pure culture of the PCB dechlorinating bacteriumDehalobium chlorocoerciaDF-1 also yielded heterologous results with significant dechlorination of weathered PCBs observed in one location. The detection of indigenous PCB dehalorespiring activity combined with the detection of putative dechlorinating bacteria and biphenyl dioxygenase genes in the soil aggregates suggests that the potential exists for complete mineralization of PCBs in soils. However, in contrast to sediments, the heterologous distribution of microorganisms, PCBs, and inhibitory cocontaminants is a significant challenge for the development ofin situmicrobial treatment of PCB impacted soils.

scholarly journals Removal of Cd(II) from Micro-Polluted Water by Magnetic Core-Shell Fe3O4@Prussian Blue

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2497
Author(s):  
Xinxin Long ◽  
Huanyu Chen ◽  
Tijun Huang ◽  
Yajing Zhang ◽  
Yifeng Lu ◽  
...  
Keyword(s):  
Prussian Blue ◽  
Co Adsorption ◽  
Magnetic Core ◽  
Diameter Distribution ◽  
Polluted Water ◽  
Core Shell ◽  
Freundlich Model ◽  
Rate Limiting Step ◽  
Rate Limiting

A novel core-shell magnetic Prussian blue-coated Fe3O4 composites (Fe3O4@PB) were designed and synthesized by in-situ replication and controlled etching of iron oxide (Fe3O4) to eliminate Cd (II) from micro-polluted water. The core-shell structure was confirmed by TEM, and the composites were characterized by XRD and FTIR. The pore diameter distribution from BET measurement revealed the micropore-dominated structure of Fe3O4@PB. The effects of adsorbents dosage, pH, and co-existing ions were investigated. Batch results revealed that the Cd (II) adsorption was very fast initially and reached equilibrium after 4 h. A pH of 6 was favorable for Cd (II) adsorption on Fe3O4@PB. The adsorption rate reached 98.78% at an initial Cd (II) concentration of 100 μg/L. The adsorption kinetics indicated that the pseudo-first-order and Elovich models could best describe the Cd (II) adsorption onto Fe3O4@PB, indicating that the sorption of Cd (II) ions on the binding sites of Fe3O4@PB was the main rate-limiting step of adsorption. The adsorption isotherm well fitted the Freundlich model with a maximum capacity of 9.25 mg·g−1 of Cd (II). The adsorption of Cd (II) on the Fe3O4@PB was affected by co-existing ions, including Cu (II), Ni (II), and Zn (II), due to the competitive effect of the co-adsorption of Cd (II) with other co-existing ions.

scholarly journals Tertiary amine-catalyzed generation of chlorine dioxide from hypochlorous acid and chlorite ions

2020 ◽  
Author(s):  
Estefania Isaza Ferro ◽  
Jordan Perrin ◽  
Owain George John Dawson ◽  
Tapani Vuorinen
Keyword(s):  
Chlorine Dioxide ◽  
Tertiary Amine ◽  
Hypochlorous Acid ◽  
Suitable Candidate ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Chlorite Ions ◽  
The Stability ◽  
Rate Limiting

AbstractThe reaction between hypochlorous acid and chlorite ions is the rate limiting step for in situ chlorine dioxide regeneration. The possibility of increasing the speed of this reaction was analyzed by the addition of tertiary amine catalysts in the system at pH 5. Two amines were tested, DABCO (1,4-diazabicyclo[2.2.2]octane) and its derivative CEM-DABCO (1-carboethoxymethyl-1-azonia-4-aza-bicyclo[2.2.2]octane chloride). The stability of the catalysts in the presence of both reagents and chlorine dioxide was measured, with CEM-DABCO showing to be highly stable with the mentioned chlorine species, whereas DABCO was rapidly degraded by chlorine dioxide. Hence, CEM-DABCO was chosen as a suitable candidate to catalyze the reaction of hypochlorous acid with chlorite ions and it significantly increased the speed of this reaction even at low catalyst dosages. This research opens the door to a faster regeneration of chlorine dioxide and an improved efficiency in chlorine dioxide treatments.

A Molecular Dynamics Study of Primary Production from Shale Organic Pores

SPE Journal ◽  
2020 ◽  
Vol 25 (05) ◽  
pp. 2521-2533 ◽  
Author(s):  
Felipe Perez ◽  
Deepak Devegowda
Keyword(s):  
Fluid Transport ◽  
Pore Diameter ◽  
Fluid Model ◽  
Fluid Composition ◽  
Hydrocarbon Production ◽  
Rate Limiting Step ◽  
Wet Gas ◽  
Rate Limiting ◽  
Organic Pores

Summary We created a model of mature kerogen saturated with a black oil. Our fluid model spans light, intermediate, and long alkane chains; and aromatics, asphaltenes, and resins. The maximum pore diameter of our kerogen model is 2.5 nm. The insertion of a microfracture in the system allows us to study fluid transport from kerogen to the microfracture, which is the rate-limiting step in hydrocarbon production from shales. Our results indicate that the composition of the produced fluids changes with time, transitioning from a dry/wet gas to a gas condensate, becoming heavier with time. However, at any given time, the produced fluid is significantly lighter than the in-situ fluid. The species with the greatest mobility is methane, which is expected because it is the lightest molecule in the fluid and its ability to migrate is greater than that of all other fluid molecules. A sensitivity analysis shows that the produced fluid composition strongly depends on the initial composition of the fluids in organic pores.

Interactions of Polysilicon with Aluminum

1987 ◽  
Vol 106 ◽  
Author(s):  
G. Ottaviani ◽  
K. N. Tu ◽  
C. Nobili
Keyword(s):  
Energy Difference ◽  
Aluminum Film ◽  
Isothermal Treatment ◽  
Final States ◽  
X Ray Diffraction ◽  
Free Energy Difference ◽  
Rate Limiting Step ◽  
Constant Heating ◽  
Rate Limiting

ABSTRACTIn-situ resistivity measurements togheter with Auger electron spectroscopy, MeV 4He+ backscattering spectrometry, scanning electron microscope and x-ray diffraction have been used to investigate interactions between Al films and CVD polycristalline silicon layers deposited on thermally grown SiO2 on silicon. A sharp and well defined increase in resistivity around 450 °C has been associated to the erosion of the polysilicon and growth of Si crystallites in the metal film. The kinetic of the transformation has been studied by isothermal treatment over the 390–450 °C temperature range. An activation energy of 2.2 ± 0.2 eV has been measured. Similar results have been obtained by using treatments at constant heating rate. A critical analysis of the available data suggests that the rate limiting step is the nucleation of Si grains in the aluminum film. The driving force for the process can be identified to be the free energy difference between the initial and final states.

Hydrolytic activity of alpha-amylase in anaerobic digested sludge

2005 ◽  
Vol 52 (1-2) ◽  
pp. 259-266 ◽  
Author(s):  
Y. Higuchi ◽  
A. Ohashi ◽  
H. Imachi ◽  
H. Harada
Keyword(s):  
Amylase Activity ◽  
Hydrolytic Enzymes ◽  
Hydrolytic Activity ◽  
Alpha Amylase ◽  
Digested Sludge ◽  
Rate Limiting Step ◽  
Degrading Bacteria ◽  
Mechanism Of Hydrolysis ◽  
Rate Limiting

Hydrolysis is usually considered to be a rate-limiting step in anaerobic digestion. For improving anaerobic solid waste treatments, it is essential to elucidate the mechanism of hydrolysis. In this study, alpha-amylase, one of the hydrolytic enzymes, was investigated for the elucidation of more precise mechanism of hydrolysis. Alpha-amylase activity of solid starch-degrading bacteria (SDB) was estimated through batch experiments with several different substrates and with distinction between cell-bound and cell-free alpha-amylase. Monitoring of newly isolated strains of SDB was done by fluorescence in situ hybridization. Results indicated that cell-bound alpha-amylase is chiefly responsible for the hydrolysis in the digested sludge, providing very useful information that the contact between microbial cells and solids is significantly important. The activity of alpha-amylase of the digested sludge remained quite low when not required, but increased as they recognized appropriate substrates. Several-fold higher activity was obtained for starch or maltose as compared to glucose only.

scholarly journals Using sound pulses to solve the crystal-harvesting bottleneck

2018 ◽  
Vol 74 (10) ◽  
pp. 986-999 ◽  
Author(s):  
Yasmin N. Samara ◽  
Haley M. Brennan ◽  
Liam McCarthy ◽  
Mary T. Bollard ◽  
Denise Laspina ◽  
...  
Keyword(s):  
High Throughput Screening ◽  
Acoustic Pulse ◽  
Fourth Generation ◽  
Chemical Library ◽  
Rate Limiting Step ◽  
Fragment Library ◽  
Sound Pulses ◽  
Rate Limiting ◽  
Air Column

Crystal harvesting has proven to be difficult to automate and remains the rate-limiting step for many structure-determination and high-throughput screening projects. This has resulted in crystals being prepared more rapidly than they can be harvested for X-ray data collection. Fourth-generation synchrotrons will support extraordinarily rapid rates of data acquisition, putting further pressure on the crystal-harvesting bottleneck. Here, a simple solution is reported in which crystals can be acoustically harvested from slightly modified MiTeGen In Situ-1 crystallization plates. This technique uses an acoustic pulse to eject each crystal out of its crystallization well, through a short air column and onto a micro-mesh (improving on previous work, which required separately grown crystals to be transferred before harvesting). Crystals can be individually harvested or can be serially combined with a chemical library such as a fragment library.

High-temperature Dislocation-precipitate Interactions in Al Alloys: An in situ Transmission Electron Microscopy Deformation Study

2005 ◽  
Vol 20 (7) ◽  
pp. 1792-1801 ◽  
Author(s):  
B.G. Clark ◽  
I.M. Robertson ◽  
L.M. Dougherty ◽  
D.C. Ahn ◽  
P. Sofronis
Keyword(s):  
High Temperature ◽  
Al Alloys ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Rate Limiting Step ◽  
Transmission Electron ◽  
Deformation Processes ◽  
Temperature Interaction ◽  
Rate Limiting

The fundamental processes controlling the high-temperature interaction of dislocations with precipitates in Al-alloys were investigated in real time by deforming specimens in situ in the transmission electron microscope at elevated temperature. The observations support a bypass mechanism involving the interaction of lattice dislocations with the precipitate–matrix interface dislocations, where the rate-limiting step in the interaction is the release of the dislocation from the particle. These observations are discussed in relation to high-temperature deformation processes and models.

Capabilities of Four Microorganisms for Bioremediation of Lead Contaminated Soil

2020 ◽  
Vol 838 ◽  
pp. 125-134
Author(s):  
Edobor Kingsley Osagie
Keyword(s):  
Contaminated Soils ◽  
Lead Concentration ◽  
Soil Samples ◽  
Decision Makers ◽  
Pseudomonas Sp ◽  
Bacillus Sp ◽  
E Coli ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

This work studied the potentials of indigenous Micrococcus sp., Bacillus sp., Pseudomonas sp., and Escherichia coli (E. coli) for bioremediation of lead contaminated soils collected from Amita forest in Ebonyi State of Nigeria.The organisms isolated from the soils were conditioned with the predetermined optimum factors in inoculated soil samples. The samples were tested for residual lead concentration at times 8, 16, 24, 32, 40, 48, and 56 days with Atomic Absorption Spectrophotometer.The performances of the organisms were in the decreasing order of Micrococcus sp., Bacillus sp., Pseudomonas sp., and E. coli. Micrococcus sp. and Bacillus sp. performed earlier at time 16 days as against Pseudomonas sp., and E. coli at 24 days. The maximum efficiencies were discovered at time 56 days as 76.68%, 72.24%, 70.11% and 55.47% for Micrococcus sp., Bacillus sp., Pseudomonas sp., and E. coli respectively with respective residual concentrations of 31.55 mg/kg, 37.55 mg/kg, 40.44 mg/kg and 60.24 mg/kg at the respective efficiencies.The rates of removals were in the decreasing order of -0.0524d-1 for Pseudomonas sp., -0.0714 d-1 for Bacillus sp., -0.0743d-1 Micrococcus sp., and 0.113 d-1 E. coli. The fitted models showed diffusion as the rate-limiting step for removals by Pseudomonas sp., Bacillus sp., and Micrococcus sp.; while chemisorption was the rate-limiting step for removal by E. coli. This information will be helpful to researchers and decision makers for the remediation of lead contaminated soils.

Kinetics of the Decomposition of Crocidolite Asbestos: A Preliminary Real-Time X-Ray Powder Diffraction Study

2004 ◽  
Vol 443-444 ◽  
pp. 291-294 ◽  
Author(s):  
A.F. Gualtieri ◽  
D. Levy ◽  
M. Dapiaggi ◽  
E. Belluso
Keyword(s):  
Real Time ◽  
Powder Diffraction ◽  
Ion Diffusion ◽  
Kcal Mole ◽  
X Ray ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of

This work is a preliminary kinetic study of the crocidolite decomposition followed in situ at high temperature using real time conventional powder diffraction and DTA in the temperature range 720-795 °C. The data analysis using the Avrami models indicates that the rate limiting step of the reaction is monodimensional ion diffusion (n=0.5) with an activation energy of 129 (10)kcal/mole.

scholarly journals Oxidation of Cytochrome 605 Is the Rate-Limiting Step when Ferrimicrobium acidiphilum Respires Aerobically on Soluble Iron

2020 ◽  
Vol 86 (22) ◽  
Author(s):  
Robert C. Blake ◽  
Jessie J. Guidry ◽  
Micah D. Anthony ◽  
Bhupal Ban ◽  
Kayla A. Smith ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Ferrous Ions ◽  
Gram Positive ◽  
Oxidase Gene ◽  
Physiological Conditions ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Intact Organism ◽  
Rate Limiting

ABSTRACT Proteins that oxidize extracellular substrates in Gram-positive bacteria are poorly understood. Ferrimicrobium acidiphilum is an actinobacterium that respires aerobically on extracellular ferrous ions at pH 1.5. In situ absorbance measurements were conducted on turbid suspensions of intact Fm. acidiphilum using an integrating cavity absorption meter designed for that purpose. Initial velocity kinetic studies monitored the appearance of product ferric ions in the presence of catalytic quantities of cells. Cell-catalyzed iron oxidation obeyed the Michaelis-Menten equation with Km and Vmax values of 71 μM and 0.29 fmol/min/cell, respectively. Limited-turnover kinetic studies were conducted with higher concentrations of cells to detect and monitor changes in the absorbance properties of cellular redox proteins when the cells were exposed to limited quantities of soluble reduced iron. A single a-type cytochrome with reduced absorbance peaks at 448 and 605 nm was the only redox-active chromophore that was visible as the cells respired aerobically on iron. The reduced cytochrome 605 exhibited mathematical and correlational properties that were consistent with the hypothesis that oxidation of the cytochrome constituted the rate-limiting step in the aerobic respiratory process, with a turnover number of 35 ± 2 s−1. Genomic and proteomic analyses showed that Fm. acidiphilum could and did express only two a-type heme copper terminal oxidases. Cytochrome 605 was associated with the terminal oxidase gene that is located between nucleotides 31,090 and 33,039, inclusive, in the annotated circular genome of this bacterium. IMPORTANCE The identities and functions of proteins involved in aerobic respiration on extracellular ferrous ions at acidic pH are poorly understood in the four phyla of Gram-positive eukaryotes and archaea where such activities occur. In situ absorbance measurements were conducted on Fm. acidiphilum as it respired on extracellular iron using an integrating cavity absorption meter that permitted accurate optical measurements in turbid suspensions of the intact bacterium under physiological conditions. The significance of these measurements is that they permitted a direct spectrophotometric examination of the extents and rates of biological electron transfer events in situ under noninvasive physiological conditions without disrupting the complexity of the live cellular environment. One thing is certain: one way to understand how a protein functions in an intact organism is to actually observe that protein as it functions in the intact organism. This paper provides an example of just such an observation.

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