CR-39 Nuclear Track Detectors for identification of Pu-239 and Am-241 alpha contamination

Nuclear Track Detectors (NTD's) are used as passive systems to detect the alpha contamination on flat or semirough surfaces. The procedure for the application of these devices is simple because the detector needs only to be placed on the area to be surveyed for a short period of time, collected and chemically processed to develop the alpha tracks. For the quantification of the results, it is necessary to have a calibration procedure. This paper presents the response of CR-39 (allyl diglycol carbonate), from American Acrylics and Pershore Companies, to alpha particles from Pu-239 (5.15 MeV) and Am-241 (5.48 MeV). The methods of etching and counting are outlined, along with the achievable linearity, efficiency and reproducibility. The sensitivity to low activity levels is also discussed.Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract W-7405-ENG-48.     

Determination of multi-element profiles of soil at Visakhapatnam using EDXRF technique

In the present study attempt has been made to generate elemental profile database for major sources of soil pollution, specific to Visakhapatnam. Representative road dust and soil samples from major industrial locations were collected and analyzed for various metals distribution using EDXRF. Analysis results indicate that V and Ni were predominant at PR and Zn was found to be dominating in road dust samples. Higher concentration of Arsenic was observed at TPP as compared to all other sites. Cr was found to be dominating at TPP and SP. I _geo calculations suggest that soil is highly contaminated with heavy metal pollutants.     

Alpha-Particle Dosimetry Using Solid State Nuclear Track Detectors: Application to 222Rn and its daughters

We present a methodology for the determination of the detection efficiency of a solid state nuclear track detector for radon and its short-lived daughters. First, particular attention is paid to the -particles having energies and angles of incidence that lead to observable tracks after an adapted chemical etching. These results are then incorporated in a mathematical model to determine the theoretical radon detection efficiency of a polymeric detector placed in a cylindrical cell. When applied to LR115 and CR39 detectors, the model reveals the influence of the position of the radon daughters inside the cell. Radon daughters tend to link up with natural atmospheric aerosols and then settle on the cell's inside wall. This model allows to determine, among other things, the cell size for which the detector response is independent of the fraction daughters plated out.     

Radon Emanation in a Limestone Cave Using CR-39 and LR-115 Solid State Nuclear Track Detectors

Radon alpha-activities were evaluated in different places of a quaternary cave, by using solid state nuclear track detectors (SSNTD). The maximum activity was detected in the place more moved back of the studied cave. The ventilation phenomenon has been investigated. The radon alpha activity and uranium content according to the growth of stalagmite and stalactite samples from the cave were evaluated. A positive correlation has been shown between the uranium distribution (radon) and the stratigraphic order of the stalagmite (and stalactite) samples.     

Stratigraphical Study of Quaternary Travertine Samples by Using CR-39 and LR-115 Solid State Nuclear Track Detectors

Radon -activity, uranium content and activity ratios of uranium and thorium [A _c (²³⁸U)/A _c (²³²Th)] have been determined in different layers of stratigraphical quaternary travertine deposits in the Errachidia area (High-Atlas, Morocco), by using two solid state nuclear track detectors (SSNTD), of CR-39 and LR-115 type II. The mineralogy of samples has been determined by X-ray diffraction. Correlation between the stratigraphy, uranium content and radon -activity has been investigated. An uranium-aragonite association has been found.     

Determination of chemical form of antimony in contaminated soil around a smelter using X-ray absorption fine structure.

Only limited information is available about the behavior of antimony (Sb) in contaminated soils. However, understanding the behavior of Sb in contaminated soils is important, because the toxicity or solubility of this element depends on its chemical state. In this study, we investigated the levels of Sb and the chemical forms of Sb in the soil around a smelter using X-ray absorption fine structure (XAFS) spectra. The highest Sb concentration in the contaminated soil was 2900 mg/kg dry soil. According to Sb-K edge X-ray absorption near edge (XANE) spectra, the Sb in the soil was in the form of Sb(V) compounds. The similarity of extended XAFS (EXAFS) spectra suggests that Sb speciation was independent of the sampling site, which indicates that Sb or Sb2O3 emitted from the smelter was converted into Sb(V) compounds in the soil.     

Determination of band occupancies using fourier-transformed compton profiles

The Pattison-Williams method of using Fourier-transformed Compton profiles for obtaining Fermi momenta in simple metals is extended for inferring d- or f-band occupancies in transition metals, rare earths, etc. The new scheme is applied to our Compton profile measurements on Ni, α-Mn and β-Mn to obtain 3d occupancies.     

The Hydraulic Exchanges between the Main Water Reservoirs of the Moroccan Middle Atlas Region Measured by Solid State Nuclear Track Detectors

Uranium and thorium contents were evaluated in water samples collected from different sources of the piedmont of the Middle Atlas mountains by using two types of solid state nuclear track detectors (SSNTD). In addition, the radon (²²²Rn) and thoron (²²⁰Rn) -activities per unit volume of the water samples were also determined. The influence of the water flow rate and altitude on the radon concentration of the water samples belonging to the piedmont of the Middle Atlas mountains was investigated. The hydraulic exchanges between the Middle Atlas water reservoirs and the Turonian aquifer of the neighbouring Tadla plain have been quantified. The results were compared with data given in literature.     

Determination of minor elements in soil profiles by neutron activation analysis

Soil samples are often used in an effort to place a suspect at a particular location, i. e., material from the suspect's shoes, clothes, car, etc. is compared with soil from the crime area. The trace element concentration in both samples has been used to establish identity; this has been obtained usually by use of neutron activation analysis. In rural areas and farms more than half a dozen different kinds of soil may be present, and each soil may consist of several horizons. Horizons in turn may be broken down into sub-horizons or transitional layers, depending upon the humus present and the amount of weathering. Thus it would appear that comparison of soil samples would require rather exhaustive knowledge of the terrain, depth, and history of the samples area since variations of the elements in the soil are affected by eluviation (washing out) or illuviation (washing in). Such variations are illustrated by showing the change of concentration of elements with soil depth. Even though most forensic applications require comparisons of only the top inch or two of soil, the samples must be classified as to depth and type of soil since man often change the soil profile (ploughing, construction, etc.), or nature does (rain, decay, etc.). We have collected a number of soil samples from a several square mile area in both the horizontal and vertical profile. These soils were dried, thoroughly mixed, and portions, irradiated for one minute (for short half-life induced activities), and one week (for long half-life activities) at a flux of ∼10 n·cm⁻²·sec⁻¹. Standards were irradiated in the same manner as samples. A number of elements were determined non-destructively; chemical separation was performed to determine others. Our results indicate great variation (factors of two or more occur in the concentration of many trace elements in going from the surface to several inches below. Similar variations occur in the horizontal plane. These data ind ate that comparison of soil samples by use of trace element concentrations is subject to considerable uncertainty. If large variations can be found within a small sampling area, the statistical significance of apparent agreement between two samples appears highly questionable. Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corporation.     

The Size Statistics of Nuclear Track Holes on the Track Membrane Surface

Areal distribution functions of double and triple pores and their first moments were obtained within the framework of the statistical model of overlapping nuclear track pores (circular holes of equal diameter on the flat surface of a track membrane). The linear dimensions of multiple pores with reference to their configuration forms (for triplets) and their dependence of on membrane porosity were calculated.     

Determination of volatile organic compounds in contaminated air using semipermeable membrane devices

Semipermeable membrane devices (SPMDs) were evaluated as passive samplers for the determination of 26 volatile organic compounds (VOCs) in contaminated air of occupational environments. A direct methodology based on the use of head-space-gas chromatography-mass spectrometry (HS-GC-MS) was developed for VOCs determinations in SPMDs, without any sample pre-treatment and avoiding the use of solvents. A desorption temperature of 150 °C for 10 min was sufficient for a sensitive VOCs determination providing limits of detection in the range of 15 ng SPMD⁻¹ for 21 of 26 studied compounds. Linear and equilibrium uptake models were established for each VOC from compound isotherms. Highly volatile compounds were slightly absorbed and moderately volatile compounds were strongly absorbed by SPMDs. This study is the first precedent of the use of SPMDs for the simultaneous sampling of a wide number of VOCs. The use of SPMDs is a simple and low cost alternative to ordinary sampling devices such as Radiello^® diffusive samplers or badge-type solid-phase supports.     

Bioenergetics and bioremediation of contaminated soil

The microbial biodegradation of xenobiotic compounds in soil and ground water is constrained by the laws of thermodynamics. Bioremediation is being investigated in a rhizosphere environment in which higher plants provide carbon and energy to sustain the microbial population. Toluene, phenol, trichloroethylene and trichloroethane have been fed in separate experiments to a pilot scale system with alfalfa growing in sandy soil containing less than 10% of silt. It is well known that microbial populations are numerous in the root zone of healthy vegetation. Root exudates can stimulate aerobic microbial biodegradation of compounds which by themselves support growth poorly or not at all. Polynuclear aromatic compounds such as phenanthrene, anthracene, and pyrene, which are not very soluble in water, and chlorinated aliphatic hydrocarbons such as trichloroethylene are examples of compounds that can be biodegraded in the rhizosphere when root exudates are present to enhance and sustain microbial activity. Solar driven transport processes such as water and solute movements due to evapotranspiration increase the likelihood that the contaminants will come into contact with the microorganisms and be degraded. The thermodynamic and bioenergetic aspects of transport and biodegradation in the rhizosphere are examined through a review of the literature and the analysis of experimental data collected in the pilot scale system.     

Determination of carbonation profiles in non-hydraulic lime mortars using thermogravimetric analysis

The carbonation profile of material taken at various depths in a lime mortar specimen has been determined at different times from manufacture using a novel, high-speed thermogravimetric analysis (TGA) method. While conventional phenolphthalein staining suggests a sharp boundary between carbonated and non-carbonated regions, the new TGA technique shows that up to 15% (w/w) of portlandite remains uncarbonated at the exterior of the mortar and that the extent of carbonation declines linearly over up to 15 mm into the interior. The technique demonstrates the possibility of identifying the presence of Liesegang patterns by measuring variations in the concentration of Ca(OH)₂ through the depth profile.     

Extraction of uranyl ions from aqueous solutions using silica-gel-bound macrocycles for alpha contaminated waste water treatment

The efficiency for the extraction of U(VI) of new modified silica gels, namely N-tripropionate (or N-triacetate)-substituted tetraazamacrocycles-bound silica gels, has been studied. The effect of the nature of the ligand, the pH and the temperature was studied both in batch experiments as well as in continuous extraction. These silica gels are good candidates for the extraction of U(VI) when compared to a commercially available acid-type chelating resin. The breakthrough and regeneration tests showed that the total removal of U(VI) from a contaminated solution can be achieved by using a column packed with such tetraazamacrocycles-bound silica gels. Finally, the use of a modified silica gel in a pilot device allowed the total decontamination of 50 m³ of real effluents containing traces of uranium, plutonium, and americium.     

Determination of N-species in soil extracts using microplate techniques

Colourimetric methods for the determination of NO(3)(-), NH(4)(+) and total N in water extracts of soils using 96-well microplate techniques are described. Nitrate was determined by azo dye formation after reduction to NO(2)(-) using a solution of hydrazine sulphate. Ammonium in the soil extracts was purified and concentrated by diffusion as NH(3) from small volumes (750microL) of extract treated with MgO into a H(2)SO(4) collector using a double-plate, MicroResp method and subsequently determined by the Berthelot reaction. For the determination of total N, samples were oxidised with K(2)S(2)O(8) at 110 degrees C in a 96x1.1mL polytetrafluoroethylene block with a lid that closed individual wells. The oxidised solutions were transferred to standard plates for colourimetric analysis of NO(3)(-). The recovery of N, measured as NO(3)(-), from NH(4)NO(3) and a range of organic-N compounds was >95%. The limits of quantitation of the colourimetic assays were 0.020mgNL(-1) for NO(3)(-) and 0.051mgNL(-1) for NH(4)(+). The methods were tested on water extracts derived from a range of 10 nutrient poor soils from Scotland. There were acceptable linear correlations between the results obtained by established methods. For soil extracts analysed by the microplate method, the relationship for NO(3)(-) was 1.03x result from ion chromatography+0.0055 (R(2)=0.9961); for NH(4)(+) determined by the microplate method, the relationship was 0.9696xresult from a discrete analyser-0.0169 (R(2)=0.9757) and for total N determined by oxidation in the PTFE microplate the relationship was 0.9435xresult obtained by combustion+0.0489 (R(2)=0.9743). Purification of the NH(4)(+) in water extracts from the 10 different soils by the diffusion method did not result in any systematic difference (paired t-test, p=0.05) between measured concentration values determined before and after diffusion.     

The Influence of the Calcination and Water Washing Treatments on the Uranium Content in Sedimentary Phosphate Samples Using Solid State Nuclear Track Detectors and Gamma-Ray Spectrometry

The uranium and thorium contents were evaluated in the 100–400 µm granulometric fraction of different sedimentary phosphate samples by using a method based on determining the mean critical angles of etching of the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD) for detecting -particles emitted by the nuclei of the uranium-238 and thorium-232 series. Data obtained were compared with the results of -ray spectrometry measurements performed on the same samples. The influence of the calcination and water washing treatments as well as the lithology and stratigraphy on the uranium concentration of the phosphate samples was investigated.     

Anaerobic remediation of dinoseb from contaminated soil

Applied Biochemistry and Biotechnology -