M. De Bruin

Low-energy gamma rays from isotopes produced by (n, γ) reactions

In activation analysis little use has been made up till now of the X-ray spectrum and the low-energy region of the ?-ray spectrum. The possibilities of using this low-energy region have been improved considerably by the recent introduction of high-resolution semiconductor detectors designed for measuring low-energy photons, a However, a good knowledge of the composition of the low-energy spectra and of the precise ?-ray energies is required besides the already wellspecified X-ray data.2 We have therefore measured the low-energy photon spectra of isotopes and isotope mixtures produced from natural elements by (n, ?) reactions.

Selenium, mercury, arsenic and cadmium in the lifecycle of the dunlin, Calidris alpina, a migrant wader

Migrant waders accumulate pollutants from their marine moulting and wintering grounds in Western Europe. In examining the possible consequences on the reproduction of the Dunlin (Calidris alpina), it was found that no adverse effects are to be expected from selenium, mercury, arsenic or cadmium. Though selenium is accumulated in very high concentrations in the kidney, after the birds departure from the marine environment for the freshwater breeding areas, levels decline rapidly. Mercury exposure in Western Europe is not excessive, as shown by the relatively low levels in the summer plumage. Feather element concentrations proved to be a useful indicator of the different moulting and wintering areas used by the birds.

Evaluation of a system for routine instrumental neutron activation analysis

The system for routine instrumental neutron activation analysis, in use for several years at the IRI at Delft, has been evaluated. Basis of this evaluation are: quality of the results, costs per analysis, capacity and ease of operation. A comprehensive description of the analysis system and associated hardware and software is included.

AUTOMATIC INTERPRETATION OF GAMMA-RAY DATA OBTAINED IN NON-DESTRUCTIVE ACTIVATION ANALYSIS

The procedure in use at our institute for the extraction of the desired element concentrations in a sample from the peak data obtained by a spectrum analysis program, is described in detail. The method is based on the use of zinc as a single comparator and takes into consideration primary activation products as well as their daughter isotopes. After assigning isotopes to spectrum peaks on the basis of γ-ray energies, the list of possible isotopes is reduced to a list of present isotopes with their concentrations using criteria based on half life, specificity and intensity of γ-rays. For elements not observed, detection limits are estimated. The procedure has been used extensively during the last two years and has shown to produce reliable results.

The uptake and distribution of cadmium in tomato plants as affected by ethylenediaminetetraacetic acid and 2,4-dinitrophenol

The uptake and distribution of cadmium in tomato plants (Lycopersicon esculentum, Mill, cv. Tiny Tim) were examined with and without the presence of ethylenediaminetetraacetic acid (EDTA) as chelating agent and 2,4-dinitrophenol (DNP) as metabolic inhibitor. Eight-week-old intact and derooted tomato seedlings were used in hydroculture experiments with cadmium applied as (115)Cd(NO(3))(2) in a range of concentrations. Measurements of the (115)Cd content of roots, stems and leaves were carried out by gamma-ray spectroscopy. The data showed that applications of both EDTA and DNP resulted in reduced total Cd accumulation in the plants, but relatively enhanced Cd transport into the above-ground plant parts. The Cd mobility in the transport channels in the shoots was increased by EDTA in both intact and derooted plants. Application of DNP leads to increased relative Cd import to leaves in derooted plants, but a reduced import into leaves of intact plants. These results suggest that Cd-complexes are formed in root cells before root-to-shoot transport. Furthermore, initial Cd uptake may be associated with adsorption on the negative charges of the cell walls of the root system. The high Cd mobility in shoots, in experiments with intact plants and Cd-EDTA application, indicates the possibility of simultaneous uptake of Cd and EDTA, possibly as a Cd-EDTA complex.

Radioisotopic labels for blood cell survival studies: a review.

The different methods of labeling blood cells, in particular erythrocytes and platelets, for survival studies are reviewed. Besides the technical information about these procedures, attention is also paid to the indications of blood cell survival studies, the effective dose equivalent involved and the interpretation of the resulting data. In the final section the possibilities created by dual-labeling procedures are discussed.

The use of multi-element concentration datasets obtained by INAA in the identification of sources of environmental pollutants

Trace element concentration patterns can be used for the identification of objects or materials. Early applications were related to the elucidation of identity or origin of objects. Recently, a number of applications have been reported of the use of trace element concentration patterns to recognize and identify components of mixtures of materials, mainly of environmental interest. In the present paper two examples are discussed of application of Target Transformation Factor Analysis to trace element concentration patterns, to identify sources of heavy metal air pollution. The materials studied are air particulate matter and epiphytic lichens used as biological accumulator.

Present and future position of neutron activation analysis

Results are presented of the performance of INAA and RNAA when compared with other spectrometric methods for trace element analysis. Indications are given for further developments aiming at exploiting the advantage and reducing the drawbacks of these two analysis technique.

CAMAC-based instrumentation for a non-destructive neutron activation analysis system

The measuring system described in this paper, developed for non-destructive neutron activation analysis, consists of a semiconductor detector gamma-ray spectrometer and a sample changer coupled to a PDP-9 computer via a CAMAC interface system. CAMAC modules implemented in this system are an ADC interface, a sample changer control, display unit, a timer and a time-of-the-year clock. The spectra are accumulated in a section of the computer memory. The computer is further used for experiment control and for the analysis and interpretation of the measured gamma-ray spectra.

A method for the correction of self-absorption of low energy photons for use in routine INAA

Practical application of oow energy gamma rays and X-rays in I.N.A.A. was restricted because of the complexity of the X-ray spectrum and sample self-absorption. This paper describes a method for the calculation of sample self-absorption on the basis of the actual sample spectra only, as measured with a high resolution semiconductor X-ray detector. In the 20–400 keV energy range, the attenuation coefficient can be represented by a three parameter function of photon energy. This was verified by measuring the transmission of photons of different energies through a range of materials. Experiments with neutron irradiated U.S.G.S. standard reference materials with known major oxide composition showed that self-absorption thus calculated from the observed spectra is in good agreement with the results of theoretical calculations based on known attenuation coefficients.