Comparing in situ distribution coefficients and exchangeability of radiocaesium in freshwater sediments with laboratory predictions

2000 ◽  
Vol 257 (1) ◽  
pp. 29-35 ◽  
Author(s):  
A de Koning ◽  
P.A Geelhoed-Bonouvrie ◽  
R.N.J Comans
Keyword(s):  
Distribution Coefficients ◽  
Freshwater Sediments

Radiostrontium Migration from a 1953-54 Liquid Release to a Sand Aquifer

1987 ◽  
Vol 22 (1) ◽  
pp. 107-128 ◽  
Author(s):  
R.W.D. Killey ◽  
J.H. Munch
Keyword(s):  
Field Experiments ◽  
Reaction Times ◽  
Fission Products ◽  
Leading Edge ◽  
Distribution Coefficients ◽  
Linear Increase ◽  
Pore Waters ◽  
Plume Front ◽  
Sand Aquifer

Abstract Aqueous ammonium nitrate solutions containing a variety of fission products were released to an infiltration pit overlying a sand aquifer in the early 1950’s. Almost all of the undecayed 137Cs and 154Eu are still retained within the 5 m thick unsaturated zone beneath the pit. Radiostrontium, however, has moved up to 350 m through the hydrogeologically simple and fast-moving groundwater flow system; the inventory of the aquifer plume’s 90Sr content is in good agreement with the estimated initial release. Data from 6 determinations of plume front position yield a linear increase in distribution ratios for 90Sr at the leading edge, from 0.8 to 4.8 mL·g−1 between 1955 and 1983. Mean Kd’s between 3 and 9 mL·g−1 have been determined from short-term laboratory and field experiments, and the rate of advance of the plume front is expected to reach a steady state within this range. Analyses of 340 contaminated sands and associated pore waters from various locations in the plume provided in situ distribution ratios with a log mean of 12.9 mL·g−1, and with no significant variations between sediments that have been in contact with 90Sr for from 10 to 28 years. Differences between plume front distribution coefficients and the in situ values observed in older portions of the plume are explained primarily by kinetically slow chemisorption onto secondary oxide coatings on the sand surfaces. This reaction apparently has half-reaction times for both sorption and desorption of less than 2 years, and hence can be treated as an equilibrium process in long-term studies. A substantial conflict remaining in the data, however, is the rate of advance of the centre of mass of the plume. Most of the radiostrontium in the aquifer la apparently moving at a much slower rate than the log mean in situ distribution ratio would predict - one explanation for this discrepancy is that 90Sr movement is greatly retarded by volumetrically small sandy silt strata that have much higher sorption capacities than the fine to medium sands that dominate the overall aquifer sampling. A simple, conservative, model that assumes equilibrium sorption of radiostrontium predicts acceptable concentrations of radiostrontium in surface waters at the CRNL property boundary.

scholarly journals In Situ Product Recovery of Bio-Based Industrial Platform Chemicals: A Guideline to Solvent Selection

Fermentation ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 26
Author(s):  
Pieter De Brabander ◽  
Evelien Uitterhaegen ◽  
Ellen Verhoeven ◽  
Cedric Vander Cruyssen ◽  
Karel De Winter ◽  
...  
Keyword(s):  
Organic Acids ◽  
Distribution Coefficients ◽  
Product Recovery ◽  
Reactive Extraction ◽  
Solvent Mixtures ◽  
In Situ Product Recovery ◽  
Platform Chemicals ◽  
Highly Hydrophobic ◽  
Fragrance Compounds

In situ product recovery (ISPR), in the form of an extractive fermentation process, can increase productivity and product titers in the sustainable production of platform chemicals. To establish a guideline for the development of industrially relevant production processes for such bio-based compounds, a wide screening was performed, mapping the potential of an extensive range of solvents and solvent mixtures. Besides solvent biocompatibility with Saccharomyces cerevisiae, distribution coefficients of three organic acids (protocatechuic acid, adipic acid and para-aminobenzoic acid) and four fragrance compounds (2-phenylethanol, geraniol, trans-cinnamaldehyde and β-ionone) were determined. While for highly hydrophobic fragrance compounds, multiple pure solvents were identified that were able to extract more than 98%, reactive extraction mixtures were proven effective for more challenging compounds including organic acids and hydrophilic alcohols. For example, a reactive mixture consisting of 12.5% of the extractant CYTOP 503 in canola oil was found to be biocompatible and showed superior extraction efficiency for the challenging compounds as compared to any biocompatible single solvent. This mapping of biocompatible solvents and solvent mixtures for the extraction of various classes of industrial platform chemicals can be a tremendous step forward in the development of extractive fermentations.

scholarly journals Cable Bacteria in Freshwater Sediments

2015 ◽  
Vol 81 (17) ◽  
pp. 6003-6011 ◽  
Author(s):  
Nils Risgaard-Petersen ◽  
Michael Kristiansen ◽  
Rasmus B. Frederiksen ◽  
Anders Lindequist Dittmer ◽  
Jesper Tataru Bjerg ◽  
...  
Keyword(s):  
Electric Fields ◽  
Sulfide Oxidation ◽  
Sister Group ◽  
Sediment Surface ◽  
Rrna Gene ◽  
Freshwater Sediments ◽  
Electrical Currents ◽  
Content Type ◽  
Marine Cable

ABSTRACTIn marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of theDesulfobulbaceaefamily, the so-called cable bacteria. Until now, cable bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the freshwater stream Giber Å, Denmark, was incubated in the laboratory. After 2 weeks, pH signatures and electric fields indicated electron transfer between vertically separated anodic and cathodic half-reactions. Fluorescencein situhybridization revealed the presence ofDesulfobulbaceaefilaments. In addition,in situmeasurements of oxygen, pH, and electric potential distributions in the waterlogged banks of Giber Å demonstrated the presence of distant electric redox coupling in naturally occurring freshwater sediment. At the same site, filamentousDesulfobulbaceaewith cable bacterium morphology were found to be present. Their 16S rRNA gene sequence placed them as a distinct sister group to the known marine cable bacteria, with the genusDesulfobulbusas the closest cultured lineage. The results of the present study indicate that electric currents mediated by cable bacteria could be important for the biogeochemistry in many more environments than anticipated thus far and suggest a common evolutionary origin of the cable phenotype withinDesulfobulbaceaewith subsequent diversification into a freshwater and a marine lineage.

scholarly journals Metal Doping Silicates as Inorganic Ion Exchange Materials for Environmental Remediation

2021 ◽  
Author(s):  
Mamdouh Mohamed Abou-Mesalam ◽  
Mohamed Ragab Abass ◽  
Essam Saleh Zakaria ◽  
Ali Mostafa Hassan
Keyword(s):  
Ion Exchange ◽  
Environmental Remediation ◽  
Sorption Process ◽  
Distribution Coefficients ◽  
Maximum Sorption Capacity ◽  
Inorganic Ion ◽  
Liquid Solutions ◽  
Maximum Sorption ◽  
Langmuir Isotherm Model

Abstract Titano-silicate (TiSi) and in-situ dopped composites were obtained by precipitation technique. The composition of these materials was established by IR, XRD, TGA&DTA, and XRF. The capacity for Co(II), & Cd(II) ions revealed that Co-TiSi & Cd-TiSi is a higher capacity than those obtained for TiSi by 1.81, & 1.41 values, respectively. To explore the separation potentiality of Co-TiSi for studied cations distribution coefficients in HNO3 were estimated. Langmuir isotherm model is the most representative for discussing the sorption process with a maximum sorption capacity of 16.02, and 10.96 mg/g for Co(II), & Cd(II) ions, respectively. Co-TiSi is suitable for the column technique for the recovery of studied cations. The investigation proved that Co-TiSi composite is suitable for the uptake of the studied ions from liquid solutions and could be considered as potential material for the refining of effluent polluted with these ions.

Sorption of selected radionuclides on different MnO2 phases

2017 ◽  
Vol 14 (4) ◽  
pp. 207 ◽  
Author(s):  
Matthew T. Athon ◽  
Glen E. Fryxell ◽  
Chia-Ying Chuang ◽  
Peter H. Santschi
Keyword(s):  
Water Distribution ◽  
Natural Radionuclides ◽  
High Capacity ◽  
Distribution Coefficients ◽  
Close Monitoring ◽  
Gamma Spectrometer ◽  
Batch Experiments ◽  
Kd Values ◽  
Dilution Effects

Environmental contextReleases to the aquatic environment from radiological dispersal devices, accidents or leaking waste disposal sites require close monitoring for radionuclide identification. A novel in situ gamma spectrometer deployable on platforms in coastal waters can provide detailed radioisotopic, however, only after the radionuclides are pre-concentrated on efficient sorbents. Here, we report results of particle–water distribution coefficients, KD, on three novel MnO2 sorbents using a set of artificial and natural radionuclides in small batch experiments. AbstractAfter nuclear disasters, there is a need to monitor released radionuclides in aquatic systems. A novel in situ gamma spectrometer deployable on mobile and stationary platforms can detect individual radionuclides, provided concentrations are high enough. Owing to rapid dilution effects, efficient sorbents are needed for preconcentration of radionuclides. Here, we report results of particle–water distribution coefficients, KD, on three novel MnO2 sorbents mounted in high-capacity cartridges using a set of artificial (57Co, 106Ru, 125Sb, 133Ba, 137Cs) and natural (7Be, 210Pb, 233Pa, 234Th) radionuclides in small batch experiments. Compared with conventionally impregnated MnO2 sorbents, novel nanostructured MnO2 sorbents displayed superior sorption for some artificial radionuclides, displaying up to one order of magnitude greater KD values than traditionally impregnated MnO2. In particular, the log KD value of 210Pb was highest (4.48±0.23) compared with all values using the other MnO2 sorbents, whereas that of 233Pa was among the lowest (3.24±0.16). These results promise some improvements for capturing not only artificially produced radionuclides, but also naturally produced 7Be from seawater using nanostructured MnO2. We also show that colloidal forms of selected radionuclides are not captured by MnO2 phases. If they could be sorbed by another sorbent, KD values could be considerably higher for Th, Po and other radionuclides. Finally, our results might add further complexities to the discussion of the potential of Th/Pa fractionation by MnO2 phases in seawater.

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