Determination of uranium element concentration and235U isotope abundance by neutron activation analysis

A new neutron activation technique has been developed for the determination of uranium element concentration and²³⁵U isotope abundance in nuclear safeguards and reference material samples based on the activation of bare and cadmium-covered samples with different thermal to epithermal neutron flux ratios and on the combination of the two corre-sponding delayed-fission neutron measurements. The principle of the new technique can be applied also to improve multi-element neutron activation analysis.     

Moss as monitor of heavy metal deposition: Comparison of different multi-element analytical techniques

Instrumental activation analysis (INAA) based on irradiations in a nuclear reactor with particularly high relative fluxes of resonance and fast neutrons has been shown to open new possibilities for multi-element surveys of mosses used as monitors of atmospheric deposition. Comparison is made with data obtained by inductively coupled plasma-mass spectrometry (ICP-MS) and conventional INAA. Data for 15 elements not previously investigated in routine moss studies are presented, e.g., Zr, Sn, Hf, Ta, W, Au, Th, and the rare earth elements Ce, Nd, Eu, Gd, Tb, Tm, Yb, Lu. Other elements particularly well determined by this approach are Sc, Co, As, Ag, Sb, Cs, La, Sm, Th, and the non-metallic trace elements Se, Br, and I. Advantages and drawbacks with the high fast neutron component are discussed.     

Characterization of Heavy Metal Air Pollution in Romania Using Moss Biomonitoring,Neutron Activation Analysis,and Atomic Absorption Spectrometry

ABSTRACT

Heavy metal air pollution in Romania was investigated by using passive moss biomonitoring. This study is a component of an international UNECE ICP Vegetation Program – moss survey. A total of 330 samples of Hypnum cupressiforme, Hylocomium splendens, Pleurozium schreberi, and other mosses were collected in Romania in the summer and autumn of 2010. The concentrations of aluminum, cadmium, chromium, copper, iron, lead, nickel, vanadium, and zinc were determined by graphite furnace/flame atomic absorption spectrometry and instrumental neutron activation analysis. The results were statistically processed to obtain spatial distribution maps of factor scores based on elemental concentrations in the moss, together with the spatial distribution maps of heavy metals in moss. The median concentrations of cadmium, 1.20?mg/kg dry weight, and lead, 30.8?mg/kg dry weight, were high compared with other European countries. The results revealed that the atmospheric deposition of these metals is a problem in north and northwest Romania.     

Measurement of L shell X-ray fluorescence intensity ratios for some elements in the atomic number range of 66£Z£90 by photoionization of consecutive L-subshells

In 1999 investigation, the needles of Sabina chinesis L. from 11 hot spot tourist cities extending over China were collected as biomonitors for evaluation of atmospheric elemental differences in those cities. Thirty five elements were determined by instrumental neutron activation analysis (INAA). The experimental data reflected the environmental alteration in the cities that have different geographical position, population burden and industrialized level. Eventually by using the data processed by factor analysis (FA) and subsequent cluster analysis (CA), the cities were grouped into six sorts of the urban atmospheric deposition with corresponding elements.     

Sensitivity of biomonitors and local variations of element concentrations in air pollution biomonitoring

In this work, we compare the concentrations of trace elements for fourty samples of lichens, mosses and tree barks used as biomonitors in an air pollution biomonitoring study in Morocco. This comparison concerns six types of biomonitors: the lichens Xanthoria parietina, Parmelia sulcata and Evernia prunastri; the moss Hylocomium splendens and barks of cedar and cork oak. The complementarity of three analytical methods was used in order to increase the number of determined elements. These techniques are: 14 MeV neutron activation analysis, thermal neutron activation analysis using the k ₀-quasi-absolute method and X-ray fluorescence analysis. The results enabled us to compare the element accumulation sensitivity for the six biomonitors used and to study the local concentration variations versus biomonitors sizes and the height above ground of their collecting point.     

Application of neutron activation analysis to determine the contents and isotopic ratios of elements in rocks and minerals

Data on the applicability of neutron activation analysis to determine various rare and trace elements and the isotopic abundance of some of them in natural samples are discussed as relevant to the solution of various geological and geochemical problems. For the determination of minute amounts of elements from small weighed quantities of rocks and minerals a number of modifications of neutron activation analysis are used: analysis with the radiochemical separation of individual elements—RNAA (tantalum, tungsten, antimony, arsenic, molybdenum, rhenium, osmium, etc.) and analysis with semiconductor—Ge (Li)—gamma-spectrometry, which is multi-element and non-destructuve—INAA (scandium, europium, tantalum, iron caesium, rubidium, cobalt, antimony, etc.) or the combination of the latter with group radiochemical separation—IRNAA (alkaline, alkaline-earth, rare-earth elements, etc.). First steps have been made towards developing techniques for the determination of the isotopic rations of some elements by means of neutron activation method, e.g., the isotopic ratio of⁵⁸Fe/⁵⁴Fe. The accuracy of isotopic ratio determination is 1 to 3 relative per cent.     

atmospheric deposition of heavy metals around the lead and copper-zinc smelters in Baia Mare, Romania, studied by the moss biomonitoring technique, neutron activation analysis and flame atomic absorption spectrometry

The mosses Pleurozium schreberi, Pseudoscleropodium purumandRhytidiadelphus squarrosus were used as biomonitors to study the atmospheric deposition of metals around the lead and copper-zinc smelters in Baia Mare. Samples representing the last three years" growth of moss or its green part, collected on the ground at 28 sites located 2-17 km from the source area, were analyzed by instrumental neutron activation analysis using epithermal neutrons (ENAA) and by flame atomic absorption spectrometry (FAAS). A total of 31 elements were determined, including most of the heavy metals characteristic of emissions from this kind of industry. The observed data for Pb, As, Cu, and Cd are all high compared with those observed in other regions of Europe with similar industries, but the concentrations in moss approach regional background levels at a distance of about 8 km from the main source area. Factor analysis of the data distinguishes two industrial components, one characterized by Pb, Cu, As, and Sb, and another one by Zn and Cd. A strong crustal component including five major elements (Na, Mg, Al, Ti, Fe) and an additional number of trace elements (Sc, V, Cr, Cs, Ba, REE, Th) also appears to be derived mainly from industrial sources. The mean I value in the present material is 5 times lower than the corresponding level in moss in Norway, and also consistently lower than elsewhere in Europe, a fact which evidences the endemic character of the examined area due to iodine depletion.     

Resonance neutrons for determination of elemental content of moss,lichen and pine needles in atmospheric deposition monitoring

Experience in the use of epithermal neutron activation analysis (ENAA) in the monitoring of atmospheric deposition by means of moss, lichens and pine needles is summarized. It is shown that 45 elements (Mg, K, Ca, Al, Cl, Sc, V, Cr, Mn, Fe, Co, Ni (using (n,p)-reaction), Zn, Cu, As, Se, Br, Rb, Sr, Zr, Mo, Ag, Sn, Sb, I, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, Ta, W, Au, Th and U, as well as Ir and Re in pine needles in the presence of anthropogenic pollution by the nickel mining plant) are reliably determined. Examples of the use of lichens, moss and pine needles as biomonitors of atmospheric deposition in Franz Josef Land the Kola peninsula and in the Tver region are given.     

Multi-element atmospheric deposition study in Croatia

For the first time the moss biomonitoring technique and two complementary analytical techniques ? neutron activation analyses (NAA) and atomic absorption spectrometry (AAS) ? were applied to study multi-element atmospheric deposition in the Republic of Croatia. Moss samples were collected during the summer of 2006 from 98 sites evenly distributed over the country. Sampling was performed in accordance with the LRTAP Convention?-?ICP Vegetation protocol and sampling strategy of the European Programme on Biomonitoring of Heavy Metal Atmospheric Deposition. Conventional and epithermal NAA and AAS made it possible to determine concentrations of 41 elements including key toxic metals such as Pb, Cd, Hg, and Cu. Factor analysis (Principal component analysis with varimax rotation) was applied to distinguish elements mainly of anthropogenic origin from those predominantly originating from natural sources. Geographical distribution maps of the elements over the sampled territory were constructed using GIS technology. For the elements included in the European programme, the median values for Croatia were generally around the average median values observed in Europe. The Adriatic coastline of Croatia may be considered as an environmentally pristine area. This study was conducted in order to provide a reliable assessment of air quality throughout Croatia and to produce information needed for better identification of pollution sources and improving the potential for assessing environmental and health risks in Croatia associated with toxic metals.     

Comparison of 14 MeV-NAA, k0-NAA and ED-XRF for air pollution bio-monitoring

In this paper the performances and the limitations of three multi-elementary analysis techniques are compared applied to a study of air pollution biomonitoring in Morocco. These techniques are: (1) 14 MeV neutron activation analysis (14 MeV-NAA), (2) thermal neutron activation analysis using the k ₀ quasi-absolute method (k ₀-NAA) and (3) energy dispersive X-ray fluorescence analysis (ED-XRF). The experimental procedures and the control of the analytical results using certified reference materials are described and discussed. The three methods were confronted for the analysis of lichens, mosses and tree-barks. The complementarity of these methods enabled us to determine 43 elements in different samples. The most suitable method for each element was selected according to the sensitivity and selectivity necessitating the minimum corrections of the matrix effects and/or the interfering reactions.     

57Fe Mössbauer spectroscopy of banded iron formations from eastern India

Samples of the mosses Hylocomium splendens and Pleurozium schreberi, collected in the summer of 1998, were used to study the atmospheric deposition of heavy metals and other toxic elements in the Chelyabinsk Region situated in the South Urals, one of the most heavily polluted industrial areas of the Russian Federation. Samples of natural soils were collected simultaneously with moss at the same 30 sites in order to investigate surface accumulation of heavy metals and to examine the correlation of elements in moss and soil samples in order to separate contributions from atmospheric deposition and from soil minerals. A total of 38 elements (Na, Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Rb, Sr, Zr, Mo, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Yb, Hf, Ta, W, Au, Th, U) in soil and 33 elements Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Br, Rb, Ag, Sb, Cs, Ba, La, Ce, Sm, Tb, Yb, Hf, Ta, W, Au, Th, U) were determined by epithermal neutron activation analysis. The elements Cu, Cd and Pb (in moss samples only) were obtained by atomic absorption spectrometry. VARIMAX rotated principal component analysis was used to identify and characterize different pollution sources and to point out the most polluted areas.     

Determination of 22 elements in geological samples by instrumental neutron activation analysis

An instrumental neutron activation analysis (INAA) method has been developed for multi-element determination in geological samples. The INAA method consists of irradiation of samples for 90 sec at a flux of 1.0·10¹² n·cm⁻²·sec⁻¹ and determination of 12 elements by using their short-lived nuclides. Samples have been re-irradiated for 3 hrs for measuring concentrations of another 10 elements. Precision and accuracy of the INAA method have been evaluated by analysing samples and USGS standard reference materials. Precision and accuracy are within±15% and ±10%, respectively.     

Response of air-pollution biomonitors under three different meteorological conditions

Samples of Flavoparmelia caperata (L.) Hale thalli, from a clean area in northern Portugal (Baião), were transplanted into exposure locations at the western Atlantic coast (north, center and south) impacted by urban-industrial emissions and meteorologically different, for a ten-month long experiment split into five terms of assessment (two months each). Through the experiment, the sites were also monitored for atmospheric bulk deposition. Analytical techniques for determinations in lichens and bulk deposition were instrumental neutron activation analysis, atomic absorption spectrophotometry and inductively coupled plasma mass spectrometry. The results indicate that: (1) the biological signals of detached lichens are compatible with sources in the area; (2) there is an appreciable number of airborne elements significantly enriched in (exposed) lichen samples, including some of great environmental interest; and (3) the cumulative contents per unit area of detached-lichen material are likely to provide an acceptable estimate of the atmospheric availability of enriched elements, as measured by their cumulative contents in the dry residues of bulk deposition.     

Seasonal variation of natural radionuclides and some elements in plant leaves

Leaf and aerosol samples were monthly collected in Mt. Sefuri (Fukuoka Prefecture). Radioactivities of ⁷Be, ²¹⁰Pb and ⁴⁰K were determined with gamma-ray spectrometry. The concentrations of some elements in the leaf samples were determined by neutron activation analysis. Similar seasonal variation of ⁷Be and ²¹⁰Pb was observed between leaf and aerosol samples, high in spring and winter and low in summer. Correlation factors for trace elements contained in the leaf show large variations. This indicates that the contribution of two sources (atmospheric deposition and uptake from soil) is very variable.     

Neutron activation analysis without multi-element standards

The paper shows how, from the neutron irradiation of multi-element standards, one can derive neutron flux parameters for the irradiation position and, at the same time, greatly improve knowledge of nuclear data parameters, such as thermal cross sections, resonance integrals and gamma raz emission probabilities, for the nuclides concerned. It is then shown how the resulting neutron flux parameters and nuclear data parameters can be used to carry out neutron activation analysis without further irradiation of multi-element standards. The technique is applied to the analysis of Chinese geochemical reference material     

Biomonitoring of atmospheric trace element deposition around an industrial town in Ghana

Parmelia sulcata lichen species have been used to study the atmospheric deposition of heavy metals and other toxic elements around an industrial area in Ghana. Natural soil samples were collected at all the sampling points and analysed in order to investigate surface accumulation of the heavy metals. The sampling points used for the study were: Afienya, Doryemu Cemetery and Doryemu River. The surface accumulation of the heavy metals would be used to examine the correlation of the elements in the lichen and soil samples in order to separate contributions from atmospheric deposition and from that of soil minerals. Thermal neutron activation analysis techniques employing a 30 kW tank-in-pool research reactor operating at a thermal neutron flux of 5×10¹¹ s⁻¹ cm⁻² was used to determine Al, Cr, Mn, Fe, Ti, Th and V in both the lichen and soil samples. The level of contamination was quantified using the enrichment factor approach. This approach was adopted in order to ascertain whether these elements are enriched in the soil or in the atmosphere. The sampling points were enriched in the atmosphere with Cr, Mn, Fe, Ti, Th and V in the decreasing order of Afienya, Doryemu Cemetery and Doryemu River.     

Instrumental Neutron Activation Analysis (INAA) and Inductively Coupled Plasma/Mass Spectrometry (ICP-MS) for Trace Element Biomonitoring using Mosses

Two analytical methods - instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS) - were used for the trace element analysis of naturally growing mosses for a heavy metal biomonitoring survey. The techniques were applied to reference mosses to evaluate the feasibility, analytical variability, detection limits and accuracy. These parameters were evaluated using 563 mosses sampled in the 1996 French survey. All the elements of interest in the European program "Atmospheric Heavy Metal Deposition in Europe - estimation based on moss analysis" (As, Cd, Cr, Cu, Fe, Hg, Pb, Ni, V, Zn) were able to be determined by ICP-MS. INAA appeared suitable for the determination of As, Cr, Fe, Hg, V and Zn. The Cd, Cu, Ni and Pb concentrations determined by ICP-MS were preferred to the INAA results, because of increased feasibility or accuracy. The results provided by both methods on the French mosses were statistically compared for 14 elements. Significant linear correlation appeared for: Ba, Ce, Cs, La, Rb, Sm, Th and V. Among these eight elements, Ba, Cs, La and Sm concentrations determined by both methods exhibited a strong statistical similarity. The correlations obtained for As, Eu, Fe and Sb were not as strong and no correlation at all was observed for Co and Cr. These differences were attributed to instrumental factors (e.g. spectral interference occurred for both methods) or due to the sample preparation prior to ICP-MS. The consequences of such results on the regional trend evaluation of atmospheric heavy metal deposition were discussed.     

The multielement potential of fast neutron cyclic activation analysis

Cyclic neutron activation analysis (CNAA), has, in recent years been developed as a useful analytical tool for the assay of short-lived isotopes in single element situations. The work described in this paper investigates the potential of the technique for composite samples having a wide range of elements that produce short-lived and long-lived isotopes on neutron irradiation. Accelerator-derived neutrons with average energies of 3 MeV, 6MeV and 14MeV were employed in what has been dubbed Fast Neutron Cyclic Neutron Activation Analysis (FNCAA). The approach to multi-element analysis entailed: (a) determination of cycle parameters in single element samples via the reactions²⁷Al(n, p)²⁷Mg (9.6 min,E =840keV), and¹³⁷Ba(n, n)^137mBa(2.3min,E =662keV), (b) a test of the method on a composite rock sample, (c) determination of analytical sensitivities using both powdered kale and rock standards and (d) a comparison of analytical results with other techniques. The results obtained in all these measurements are presented and discussed.     

Rapid analysis of biological reference materials by instrumental neutron activation

Summary Instrumental neutron activation analysis (INAA) was applied to the rapid determination of cadmium and other elements in the IAEA biological reference material horse-kidney (H-8). Nuclear reactor neutrons and epithermal neutrons were used as neutron sources. Cadmium, bromide, iodine and phosphorus were determined by epithermal neutron activation analysis. Aluminum was determined by reactor neutron activation analysis taking into account the contribution of phosphorus to the ²⁸Al activity.     

Determination of As(III), As(V), MMA and DMA in drinking water by solid phase extraction and neutron activation

A combination of solid phase extraction, coprecipitation, and neutron activation techniques has been used to develop a speciation analysis method based on green chemistry for the major arsenic species in drinking water. Arsenate as As(V), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) are separated and preconcentrated by strongly anion and cation exchange columns in tandem while As(III) remains in the effluent. These species are then selectively eluted and As(III) coprecipitated with bismuth sulphide. This simple method has been applied to the analysis of water reference materials with good results. The detection limits are 0.9, 1.7, 1.6, 3.8 and 16 ng mL⁻¹ for As(III), As(V), MMA, DMA and total arsenic, respectively, using a neutron flux of 2.5 × 10¹¹ cm⁻² s⁻¹ at the Dalhousie University SLOWPOKE-2 reactor (DUSR) facility and anti-coincidence gamma-ray spectrometry.