Association of radionuclides with components of fulvic acids isolated from soils

The distribution of Pu and Am between specific and nonspecific components of various groups of the organic matter of soil was studied. For chernozem and soddy podzolic soil, 63 and 53% of Pu and only 1 and 8% of Am, respectively, are bound with fulvic acid purified to remove low-molecular-weight compounds by fractionation on BAU activated charcoal. Larger relative amount of Am, compared to Pu, in the form of low-molecular-weight nonspecific compounds is responsible for higher migration mobility of Am, compared to Pu, in the environment. The sorption of organic complexes of Pu and Am on carbon nanotubes was studied. The degree of Pu sorption only slightly depends on the nature of the organic substance, except solutions of humic acids from which the Pu sorption is appreciably higher. The degree of Am sorption regularly increases with a decrease in the molecular weight of the organic substances.     

Distribution of naturally occurring radionuclides in soils of the southern districts of Bangladesh

The activity concentrations of naturally occurring radioactive materials in soil samples of an elevated radiation background area of nine southern districts of Bangladesh were determined using gamma-ray spectrometry with an aim of evaluating the environmental radioactivity. The outdoor and indoor external effective dose rates and the radiation hazard indices from the soil activity were evaluated with an aim of minimising the harmful effects of ionising radiation to the population of the area concerned. The activity of (137)Cs was measured and observed in some of the locations.     

Thermophysical characteristics of aprotonic solvents and electrolytes based on them

Measured and computed values of the thermal conductivity and heat capacity of a number of organic solvents and electrolytes based on them are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 4, pp. 623–626, October, 1982.     

Effect of titanium and titania on chemical characteristics of hydroxyapatite plasma-sprayed into water

HA and its composite particles (HA/Ti, HA/TiO₂) were plasma-sprayed into water as well as on the Ti substrate, respectively. The microstructure and phase compositions of the sprayed HA and its composite particles before and after impinging on the substrate were studied by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. The results showed that the HA in the composite particles sprayed into water had a higher crystallinity than that in the composite coating. The addition of Ti or TiO₂ could both influence the decomposition of HA, but no chemical reacting product between them was formed before and after impinging on the substrate. However, EDS analyses showed the occurrence of interdiffusion of elements between HA and TiO₂, which was favorable to enhance the cohesive strength of particles in the composite coating. The post heat treatment at 650 °C for 2 h can effectively improve the crystallinity of coating by transforming amorphous phases into HA.     

Influence of EDTA washing on the species and mobility of heavy metals residual in soils

Aiming to estimate the potential risk of ethylenediaminetetraacetic acid (EDTA)-enhanced soil washing, the heavy metal species and their mobility in the washed soil under different combinations were investigated by batch leaching tests and the sequential extraction procedure. Results demonstrate that the metal removal efficiency was rather low (less than 12%), partially due to the significant Ca dissolution and strong bonding between metals and the soil as well as the insufficient EDTA dosage. The washing combination of 0.0005 M EDTA and half-an-hour washing can enhance the instant mobility of Ni, Zn and Pb possibly owing to the slow detachment of EDTA-destabilized metals. Metal fractionation also exhibits the corresponding increase in their labile exchangeable fractions. Therefore, a more concentrated EDTA solution for a longer duration often decreased their mobility. The increase in some fractions of a curtain metal implies the redistribution of this metal during the EDTA soil washing. The pathway of such a redistribution may vary for different metals, but the redistribution to organic matter is often a slow process, while that to carbonates or Fe/Mn oxides is a faster one and even may occur in a half hour washing with 0.0005 M EDTA solution. These redistribution processes may also increase the metal chemical availability. Therefore, we should prudently control the chelating reagent concentration and washing duration to finally minimize the mobility and availability of the remaining heavy metals when designing the soil washing for the remediation of metal-contaminated soils.     

Non-linear characteristics of engineering soils

The paper deals with the non-linear stress-strain characteristics of engineering soils and investigates some of the more important factors relating to the elasto-plastic behaviour. A review of previous literature describes some of the work already performed in this area of study, and discusses the applicability of the theories proposed, most of which have been established using results obtained from a standard tri-axial test. A non-linear stress-strain theory is formulated, using results from a true tri-axial test, which also takes into account the behaviour of the soil during unloading and subsequent reloading. This behaviour is shown to depend on the stress levels attained in the unloading/reloading hysteresis loop in which the reloading portion of the loop is closely linearly elastic. Finally, the suitability of the proposed equations in typical engineering calculations is discussed and a worked example is included which demonstrates how the proposed incremental stress-strain equations may be applied in analysis.

List of symbols

The notation used in the theoretical work is as follows: E modulus of elasticity of soil - H vertical depth of cavity - K ₀ coefficient of earth pressure at rest assumed constant with depth - K _r Rankine ratio=(1 – sin )/(1 + sin ) - K, K ₁,K ₂,f ₁,f ₂,g, m, n constants found experimentally - k R ₀ ²/R₁ ² - p _h stress in any horizontal direction whenp _x =P _z =P _h - p _r radial stress - p _x stress inx-direction - p _y vertical stress - p _z stress in z-direction - p _xi ,p _yi ,p _zi stress levels in co-ordinate directions at commencement of unloading/reloading cycle - p _xf ,p _yf ,p _zf stress levels in co-ordinate directions at end of unloading portion of unloading/reloading cycle - p circumferential stress - p _u ultimate pressure in cavity - R ₀ initial radius of cavity - R ₁ ultimate radius of cavity - R ₂ radius of plastic zone - r a radial distance from centre of cavity to typical element in elastic or plastic zone - r ₁,r ₂,r ₃ stress ratiosp _x (ultimate)/p _xi ,p _y (ultimate)/p _yi ,p _z (ultimate)/p _zi respectively - t step length - w radial displacement of elastic zone - soil density - average volumetric strain of plastic zone - _r volumetric strain of increment of plastic zone - _pr , _r , etc. a small increment of the quantity concerned - _r radial strain - _x strain inx-direction - _y vertical strain - _z strain inz-direction - circumferential strain - _xyi etc strain in thex-direction due to loading in-direction at commencement of unloading/reloading cycle, etc. - _xyf , etc strain in thex-direction due to loading in-direction at end of unloading portion of unloading/ reloading cycle, etc. - Poisson's ratio - angle of internal friction of soil     

Fracture characteristics of cement-stabilized soils

Fracture characteristics of cement-stabilized soil under Mode I (tensile) and Mode II (in-plane shear) were investigated on a series of cube specimens. The linear elastic fracture mechanics approach was applied to study the stress distribution in the specimens and also to determine the constitutive equations for fracture parametersK _I andK _II. The experimental studies were carried out on a range of 100 mm soil-cement cube specimens modified for fracture testing by inserting a series of slots. It was shown that results predicted by numerical models were in acceptable agreement with the experimental observations. The fracture parameterK _I was found to be in the range 0.11–0.17 MN m^−3/2 and the parameterK _II in the range 0.31–0.45 MN m^−3/2. This result indicated that the soil-cement exhibited a greater resistance to shear fracture than was expected.     

Adsorption and mobility of Cr(III)-organic acid complexes in soils

The soluble Cr(III) is likely to be complexed with organic ligands in ligand-rich soil. Cr(VI) chemical reduction by organic acids and bioreduction by microorganisms can produce soluble Cr(III)-organic acids complexes. Thus, it is of great significance to investigate the absorption and mobility of Cr(III)-organic acid complexes in soils. In this study, Cr(III)-EDTA and Cr(III)-cit were prepared and purified, and then were examined for adsorption and mobility. The results demonstrated that Cr(III) was strongly bound to soil, while Cr(III)-organic acid complexes had no or slight interaction with soils since Cr(III)-EDTA and Cr(III)-cit complexes mainly existed as the forms of [Cr(III)-EDTA]⁻ and [Cr(III)-cit], respectively, under the tested conditions with initial pH 4.0-9.0. The adsorption of Cr(III) increased but that of Cr(III)-organic acid complexes decreased with the content of soil organic matter. Compared with Cr(III)-EDTA, the mobility of Cr(III)-cit in soil columns was reduced, due to the specific adsorption between soils and Cr(III)-cit which contained one free hydroxyl group.     

Genotoxic endpoints in the earthworms sub-lethal assay to evaluate natural soils contaminated by metals and radionuclides

Eisenia andrei was exposed, for 56 days, to a contaminated soil from an abandoned uranium mine and to the natural reference soil LUFA 2.2. The organisms were sampled after 0, 1, 2, 7, 14 and 56 days of exposure, to assess metals bioaccumulation, coelomocytes DNA integrity and cytotoxicity. Radionuclides bioaccumulation and growth were also determined at 0 h, 14 and 56 days of exposure. Results have shown the bioaccumulation of metals and radionuclides, as well as, growth reduction, DNA damages and cytotoxicity in earthworms exposed to contaminated soil. The usefulness of the comet assay and flow cytometry, to evaluate the toxicity of contaminants such as metals and radionuclides in earthworms are herein reported. We also demonstrated that DNA strand breakage and immune cells frequency are important endpoints to be employed in the earthworm reproduction assay, for the evaluation of soil geno and cytotoxicity, as part of the risk assessment of contaminated areas. This is the first study that integrates DNA damage and cytotoxicity evaluation, growth and bioaccumulation of metals and radionuclides in a sub lethal assay, for earthworms exposed to soil contaminated with metals and radionuclides.     

Effect of substrates on the chemical characteristics and evolving structures of an organic superhydrophobic coating

While recent research has used organic coatings to replace chromium-based coatings, the ability of a coating material to repeat its chemical properties on different substrates is still under investigation. The Repellix superhydrophobic compound was developed and deposited on three different substrates using the atomic layer deposition method under the same condition. The films were characterized using the scanning electron microscope, atomic force microscope, water contact angle, attenuated Fourier transform infrared, and x-ray diffractometer. The surface morphology revealed that microstructural evolutions and topologies are different. The roughness of the coating deposited on stainless steel is the highest at 38.39 nanometers, while mild steel substrate showed the least surface roughness at 28.66 nanometers. From observations, the roughness also contributed to the degree of superhydrophobicity of the films deposited on substrates. The multiple hydroxyl functional groups observed in the Fourier transform spectroscopy in the range 3200 cm⁻¹ to 4000 cm⁻¹ would aid the adhesion of deposited films to the substrates. The x-ray diffraction results showed that all substrates had chemical stability, and the Repellix compound is amorphous on all substrates. Stainless steel showed to be the most robust among the substrates considered.     

Ion mobility spectrometry and its applications in detection of chemical warfare agents

When fast detection of chemical warfare agents in the field is required, the ion mobility spectrometer may be the only suitable option. This article provides an essential survey of the different ion mobility spectrometry detection technologies. (To listen to a podcast about this feature, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html.).     

Sorption characteristics of materials of the filtration barrier in upper aquifers contaminated with radionuclides

Sorption and desorption characteristics of natural materials (apatite, vermiculite, haydite, wood sawdust, perlite, zeolite produced by Tseolit-Treid, shungite) were studied, and the possibility of using them in filtration barriers in upper aquifers contaminated with cesium, strontium, uranium, and technetium was discussed. Changes in the sorption properties of the materials under the action of natural groundwater microflora were evaluated. Under the conditions of the barrier operation, microbiological action does not significantly affect the sorption characteristics of the materials studied.     

Effect of caged fluorescent dye on the electroosmotic mobility in microchannels

We report on measurements of electroosmotic mobility in polymer microchannels and silica capillaries with and without the addition of a caged fluorescein dye to the buffer. For PMMA microchannels, the mobility was found to increase from (2.6 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) to (4.6 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) upon addition of 1.2 mmol/L of caged dye. For PC microchannels, the mobility increased from (4.3 +/- 0.2) x 10(-4) cm2 V(-1) s(-1) to (5.4 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) upon addition of caged dye. For PDMS microchannels, the mobility increased from (4.3 +/- 0.2) x 10(-4) cm2 V(-1) s(-1) to (6.4 +/- 0.5) x 10(-4) cm2 V(-1) s(-1) upon addition of caged dye. For fused-silica capillaries, the mobility ((5.5 +/- 0.2) x 10(-4) cm2 V(-1) s(-1)) was unaffected by the addition of the caged dye.     

Acidic‐basic interactions in tungstate melts based on tungsten electroplating out of them

Based on thermodynamic calculations of possible reactions of interaction between sodium tungstate and oxygen‐containing compounds of boron, carbon, phosphor, sulphur, metals of VI‐B group the probability of possible reactions was evaluated. The experimental verification of the assumptions was accomplished by the methods of potentiometry and IR‐spectroscopy. The possibility of existence of equilibrium (reversible) melted systems with the electrodes from metals of VI‐B group and their carbides was proved by the electrochemical measurements and thermodynamic calculations.     

Temperature dependence of the thermophysical characteristics of oligomers and cross-linked polymers based on them

The results of an analysis of the experimental values of the thermophysical characteristics of oligomers which are distinguished by a long and flexible oligomer block and cross-linked polymers based on them in the temperature range 90–373°K are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 35, No. 4, pp. 622–627, October, 1978.     

Effect of complexing agents and surfactants on coprecipitation of cesium radionuclides with nickel ferrocyanide

The effect of organic complexing agents and surfactants on coprecipitation of Cs tracer with nickel ferrocyanide was studied. In the presence of oxalate and ethylenediaminetetraacetate anions in solutions, the degree of Cs coprecipitation sharply decreases. The effect of surfactants of various kinds on coprecipitation is considerably weaker. To decrease the interfering effect of organic substances on the coprecipitation of Cs, their treatment with ozone was tested. The ozonation of solutions was found to eliminate completely the negative effect of organic complexing agents and surfactants on the Cs coprecipitation with nickel ferrocyanide.     

Cosorption of zinc and glyphosate on two soils with different characteristics

Agricultural application of large amounts of glyphosate [N-(phosphonomethyl)-glycine] may affect soil metal behaviors to some extend, because glyphosate can react with many kinds of metals to form metal complexes. Cosorption of Zn and glyphosate on a Red soil (RS, Udic Ferrosols) and a Wushan soil (WS, Anthrosol) was studied. In comparison with the WS, the RS has less adsorption capacity for Zn and higher for glyphosate. The presence of glyphosate decreased Zn adsorption on the two soils, which are resulted from the decreased equilibrium solution pH caused by the added glyphosate, and also the formation of water-soluble complexes of glyphosate with solution Zn(2+) that had lower affinity to soil surface in comparison with Zn(2+) itself. Such effect is more significant on the RS than on the WS, mainly because of the less adsorption quantity of Zn on the former one. On the contrary, the presence of Zn increased the adsorption quantities of glyphosate on the RS and WS, which is resulted from the decreasing pH value of the equilibrium solution caused by Zn(2+) exchange with H(+) ions of soil surface. Such results suggest that glyphosate in field may increase the mobility and bioavailability of Zn and correspondingly increase its environmental risk.