Influence of Micro Environments and Microorganisms on the Transport Properties of Redox-Sensitive Elements (E.G. Technetium)

1990 ◽  
Vol 212 ◽  
Author(s):  
Hanskarl Brühl ◽  
Asaf Pekdeger ◽  
Andreas Winkler
Keyword(s):  
Transport Properties ◽  
Laboratory Experiments ◽  
Microbial Metabolism ◽  
Mineral Surfaces ◽  
Microbial Activities ◽  
Transport Behaviour

ABSTRACTIn laboratory experiments immobilisation of Tc under oxic conditions was observed. The transport behaviour of redox-sensitive elements is not only controlled by the geochemical “frame conditions” which can be measured within the macro environment. Immobilisation behaviour of Tc strongly depends on micro environments and on microbial metabolism. Micro environments which may develope on the mineral surfaces can detoriate the mobility of Tc, furthermore the fixation of Tc is influenced by microbial activities.

scholarly journals Sorption and Desorption of Vanadate, Arsenate and Chromate by Two Volcanic Soils of Equatorial Africa

Soil Systems ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 22
Author(s):  
Sara Gonzalez-Rodriguez ◽  
Maria Luisa Fernandez-Marcos
Keyword(s):  
Laboratory Experiments ◽  
Sorption Isotherms ◽  
Soil Samples ◽  
Mineral Surfaces ◽  
Volcanic Soils ◽  
Iron Species ◽  
Freundlich Model ◽  
Equatorial Africa ◽  
Relevant Role ◽  
Icp Mass Spectrometry

Sorption of oxyanions by soils and mineral surfaces is of interest due to their role as nutrients or pollutants. Volcanic soils are variable charge soils, rich in active forms of aluminum and iron, and capable of sorbing anions. Sorption and desorption of vanadate, arsenate, and chromate by two African andosols was studied in laboratory experiments. Sorption isotherms were determined by equilibrating at 293 K soil samples with oxyanion solutions of concentrations between 0 and 100 mg L−1 V, As, or Cr, equivalent to 0−2.0 mmol V L−1, 0−1.3 mmol As L−1, and 0−1.9 mmol Cr L−1, in NaNO3; V, As, or Cr were determined by ICP-mass spectrometry in the equilibrium solution. After sorption, the soil samples were equilibrated with 0.02 M NaNO3 to study desorption. The isotherms were adjusted to mathematical models. After desorption with NaNO3, desorption experiments were carried out with a 1 mM phosphate. The sorption of vanadate and arsenate was greater than 90% of the amount added, while the chromate sorption was much lower (19–97%). The sorption by the Silandic Andosol is attributed to non-crystalline Fe and Al, while in the Vitric Andosol, crystalline iron species play a relevant role. The V and Cr sorption isotherms fitted to the Freundlich model, while the As sorption isotherms conformed to the Temkin model. For the highest concentrations of oxyanions in the equilibrating solution, the sorbed concentrations were 37–38 mmol V kg−1, 25 mmol As kg−1, and 7.2–8.8 mmol Cr kg−1. The desorption was low for V and As and high for Cr. The comparison of the sorption and desorption isotherms reveals a pronounced hysteresis for V in both andosols and for Cr in the Silandic Andosol. Phosphate induced almost no V desorption, moderate As desorption, and considerable Cr desorption.

Review of Pc-Sw Data for Network Model Validation

2010 ◽  
Vol 2 ◽  
pp. 15-30
Author(s):  
O.A. Olafuyi
Keyword(s):  
Experimental Data ◽  
Transport Properties ◽  
Laboratory Experiments ◽  
Network Models ◽  
Micro Ct ◽  
Pore Scale ◽  
Predictive Capability ◽  
Flow Transport ◽  
Scale Network ◽  
Pore Scale Network

Advances in micro-CT imaging of porous materials provide the opportunity to extract representative networks from the images. This improves the predictive capability of pore scale network models to predict multiphase flow transport properties. However, all these predictions need to be validated with laboratory experimental data. The experimental data for such validation may either be from the literature or newly conducted laboratory experiments on same outcrops. This paper presents the review of some of the available Pc – Sw experimental data available in the literature for validating the predictions made by network models.

The cycle of atmospheric nitrous oxide

1979 ◽  
Vol 290 (1376) ◽  
pp. 495-504 ◽  
Keyword(s):  
Laboratory Experiments ◽  
Nitrogen Fertilizers ◽  
Time Range ◽  
Microbial Activities ◽  
Electrical Discharges ◽  
Soil Systems ◽  
To Come ◽  
Turn Over ◽  
Over Time ◽  
Horizontal And Vertical Distribution

An attempt has been made to construct an N 2 O balance of the troposphere in order to demonstrate the state of knowledge of the cycle of atmospheric N 2 O. This balance has been constructed considering the parameters relevant for atmospheric N 2 O as far as known such as the horizontal and vertical distribution in the atmosphere and in the oceans, the variation of the atmospheric mixing ratio with time, the fluxes in the air-sea and in the air-soil systems, and man-made fluxes. The total atmospheric burden of N 2 O appears to be in the range 1600-2100 Mt, the tropospheric turn-over time between 4 and 12 years. Most of the atmospheric N 2 O seems to originate from microbial activities at the Earth’s surface with the oceans apparently being the major source with about 35 % of the total source as obtained from the tropospheric N 2 O mass and turn-over time (range of uncertainty 5-100 %) followed by soil and fresh water with about 25 % of the total source (range of uncertainty 4-100 %) including the contribution of industrial nitrogen fertilizers with about 10 % of the total source (range of uncertainty 2-24 %). Direct man-made N 2 O sources seem to be relatively small with about 2 % of the total source (range of uncertainty 0.5-5 %), but may grow considerably in the future. The N 2 O production by chemical reactions in the troposphere itself (e.g. electrical discharges) is not known; a figure of between 3 and 70 % of the total source has been inferred from laboratory experiments. The sinks of atmospheric N 2 O are poorly known. The only known major N 2 O destruction appears to occur in the stratosphere. The rate of transport into the stratosphere, however, limits this sink to about 10 % of the total amount of N 2 O to be destroyed under steady state conditions (range of uncertainty 3-22 %). The major problem of the cycle of atmospheric N 2 O is the unknown main sink. Since the stratosphere does not seem to come into question, the missing sink should be found somewhere in the troposphere, pedosphere, and/or hydrosphere.

scholarly journals Adsorption of RNA on mineral surfaces and mineral precipitates

2017 ◽  
Vol 13 ◽  
pp. 393-404 ◽  
Author(s):  
Elisa Biondi ◽  
Yoshihiro Furukawa ◽  
Jun Kawai ◽  
Steven A Benner
Keyword(s):  
Calcium Carbonate ◽  
Periodic Table ◽  
Alkaline Earth ◽  
Laboratory Experiments ◽  
Mineral Surfaces ◽  
Carbonate Minerals ◽  
Natural Mineral ◽  
Large Molecules ◽  
Polymorphic Forms ◽  
Differential Binding

The prebiotic significance of laboratory experiments that study the interactions between oligomeric RNA and mineral species is difficult to know. Natural exemplars of specific minerals can differ widely depending on their provenance. While laboratory-generated samples of synthetic minerals can have controlled compositions, they are often viewed as "unnatural". Here, we show how trends in the interaction of RNA with natural mineral specimens, synthetic mineral specimens, and co-precipitated pairs of synthetic minerals, can make a persuasive case that the observed interactions reflect the composition of the minerals themselves, rather than their being simply examples of large molecules associating nonspecifically with large surfaces. Using this approach, we have discovered Periodic Table trends in the binding of oligomeric RNA to alkaline earth carbonate minerals and alkaline earth sulfate minerals, where those trends are the same when measured in natural and synthetic minerals. They are also validated by comparison of co-precipitated synthetic minerals. We also show differential binding of RNA to polymorphic forms of calcium carbonate, and the stabilization of bound RNA on aragonite. These have relevance to the prebiotic stabilization of RNA, where such carbonate minerals are expected to have been abundant, as they appear to be today on Mars.

Decomposition studies on New Zealand and antarctic lichens

1993 ◽  
Vol 25 (1) ◽  
pp. 73-82 ◽  
Author(s):  
L. G. Greenfield
Keyword(s):  
New Zealand ◽  
Low Temperature ◽  
Laboratory Experiments ◽  
Soil Microbes ◽  
Dry Weight ◽  
Microbial Metabolism ◽  
Soil Animal ◽  
Short Term

AbstractThe decomposition of ground, dead (oven-dried) lichens has been studied in laboratory experiments that aimed to simulate decomposition in nature. Enzymes, common in soil animal guts and soil microbes, solubilized 29% of the lichen weight and 25% of lichen nitrogen. Approximately 9% of lichen nitrogen was mobilized to mineral forms during 97 days' incubation in soil or sand. Low moisture levels reduced the amount of nitrogen mobilized. In short-term (30 days) incubation studies, lichens at optimum moisture but low temperature lost 9% of their initial dry weight due to microbial metabolism. In contrast, lichens incubated for 30 and 135 days at similar moisture levels but higher temperatures lost 19% and 30% respectively of their initial dry weight due to microbial metabolism.

Room temperature discotic liquid crystalline triphenylene-pentaalkynylbenzene dyads as an emitter in blue OLEDs and their charge transfer complexes with ambipolar charge transport behaviour

2019 ◽  
Vol 7 (19) ◽  
pp. 5724-5738 ◽  
Author(s):  
Indu Bala ◽  
Wan-Yun Yang ◽  
Santosh Prasad Gupta ◽  
Joydip De ◽  
Rohit Ashok Kumar Yadav ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Charge Transport ◽  
Transport Properties ◽  
Liquid Crystalline ◽  
Room Temperature ◽  
Charge Transfer Complexes ◽  
Transport Behaviour

Room temperature discotic dyads as emitters in blue OLEDs and their TNF complexes with ambipolar charge transport properties.

The temperature-dependent effect of residual nematicides on the activities of soil microorganisms

1973 ◽  
Vol 19 (7) ◽  
pp. 855-859 ◽  
Author(s):  
C. M. Tu
Keyword(s):  
Organic Nitrogen ◽  
Laboratory Experiments ◽  
Soil Microorganisms ◽  
Sulfur Oxidation ◽  
Microbial Activities ◽  
Temperature Dependent ◽  
Dependent Effect ◽  
Ammonium Production ◽  
Inhibition Of Nitrification ◽  
Fungal Populations

The effects of Dasanit®, carbofuran, D–D®, and Vorlex® on microbial activities in a loamy sand were evaluated in laboratory experiments at temperatures of 5 and 28C. Bacterial and fungal populations initially decreased with some of the fumigant treatments but the populations recovered after 2 weeks. D–D and Vorlex significantly stimulated ammonification of soil native organic nitrogen at 28C after 4 weeks. In some instances, fumigants decreased ammonium production from added peptone at low temperature. No inhibition of nitrification and sulfur oxidation was evident with any of the nematicides. The effect of fumigant and glucose treatments on the respiration of microorganisms at 15 and 30C showed that the inhibition period observed in the early stages of incubation was negatively correlated with the soil temperature.

Covering of cometary nucleus by refractory crust and its evolution into asteroid-like body

1999 ◽  
Vol 173 ◽  
pp. 365-370
Author(s):  
Kh.I. Ibadinov
Keyword(s):  
Laboratory Experiments ◽  
Cometary Nucleus ◽  
Sublimation Rate ◽  
Cometary Nuclei ◽  
Short Period Comet ◽  
Short Period ◽  
Brightness Decrease ◽  
Crust Thickness ◽  
Ice Sublimation ◽  
Period Comet

AbstractFrom the established dependence of the brightness decrease of a short-period comet dependence on the perihelion distance of its orbit it follows that part of the surface of these cometary nuclei gradually covers by a refractory crust. The results of cometary nucleus simulation show that at constant insolation energy the crust thickness is proportional to the square root of the insolation time and the ice sublimation rate is inversely proportional to the crust thickness. From laboratory experiments resulted the thermal regime, the gas productivity of the nucleus, covering of the nucleus by the crust, and the tempo of evolution of a short-period comet into the asteroid-like body studied.

Spectroscopic Diagnostics of Tokamaks

1988 ◽  
Vol 102 ◽  
pp. 165-174
Author(s):  
C. de Michelis
Keyword(s):  
Transport Properties ◽  
Power Losses ◽  
Spectroscopic Diagnostics ◽  
Important Concern

AbstractImpurities being an important concern in tokamaks, spectroscopy plays a key role in their understanding. Techniques for the evaluation of concentrations, power losses and transport properties are surveyed, and a few developments are outlined.

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