J Boman

Time and position dependent artefacts in X-ray spectra from a Si(Li) detector

The background levels in X-ray spectra from a Si(Li) detector have been studied in two different ways. First, an increasingly larger area of the detector was irradiated and significant changes in the resulting spectra were observed. Secondly, the detector was scanned across a diagonal and the detection efficiency was measured. Both methods showed that the active area as given by the manufacturer was significantly larger than that which could be irradiated without degradation of X-ray spectra. Furthermore, it is shown that the detector performance changed drastically with the time since the bias was applied. Artefacts and a general increase in the background reduced the usable detector area with 20% after twelve hours. In a normal analysis this gives rise to an increase in detection limits of up to 65% for an aerosol sample as compared to the detection limits when bias just has been applied.

EDXRF and ICP-MS analysis of environmental samples

In an inter-analytical method comparison, energy-dispersive x-ray fluorescence (EDXRF) (radioactive source and x-ray tube based systems), inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GF-AAS) analyses were carried out on seven international biological reference materials and environmental samples. Good agreement was found between the different techniques. EDXRF and ICP-MS were used to determine 28 elements such as S, P, K, Ca, V, Co, Cr, Ni, Ti, Fe, Cu, Zn, Rb, Sr, Cd, As, Pb, Tl, Mo, U, Th and Hg in environmental samples (coal, trees, water, vegetation and fish) collected in a coal mining area of Vietnam. The results show that the impact of coal can be seen through elevated concentrations of S, Ni, Zn, Cd, As, Hg and U in several of the samples.

Inorganic element concentrations in near surface aerosols sampled on the northwest slopes of Mount Kenya

Abstract Eight trace elements, Si, Cl, K, Ca, Ti, Mn, Fe and Zn in the near-ground atmospheric aerosols were evaluated in the northwestern part of Mount Kenya using a dichotomous sampler and an EDXRF spectrometer. The samples were taken at 2 sites situated in Nanyuki area, which is roughly on the Equator. The sampler segregated the aerosol into two aerodynamic diameter (ad) size fractions, fine ( 3.5 and

Improved technique for quantitative EDXRF analysis of powdered plant samples

An improved technique for energy-dispersive x-ray fluorescence analysis of powdered plant samples is presented. It is based on the use of a special rotating and moveable sample holder (RMSH). This sample holder provides both controlled rotation and lateral transfer movements of the sample while a measurement is carried out, consequently simulating homogeneous excitation conditions over the sample. In this way it compensates for effects caused by the typical inhomogeneous distribution of intensity within the x-ray beam exciting the elements in the sample. The sample consists of powdered dry plant material deposited in an easy way on an adhesive tape, providing a stable layer of plant particles covering the surface. The mean size of the particles fixed on the tape results in a thin or intermediate thickness sample, 0.8-2.5 mg cm -2 . The application of RMSH provides an easy sample preparation method and improved performance, lowering the detection limits of the measurements and resulting in reproducible, reliable and consistent data.

Concentrations of some elements in and on Scots pine needles

Elemental concentrations in needles from individual Scots pine trees (Pinus sylvestris L.) from four different sites in Latvia were determined. P, S, K, Ca, Mn, Fe, Cu, Zn, Rb and Sr were simultaneously determined by total-reflection x-ray fluorescence and Cr, Co, Ni, Cd, Pb were measured using multi-element graphite furnace atomic absorption spectrometry. The elemental concentrations obtained after washing the pine needles with water and with chloroform were compared with those obtained without washing. Chloroform was a more effective washing agent for the removal of airborne deposits from the surface of the needles. The comparison of the chemical compositions of pine needles that were unwashed or washed with chloroform allowed the trace elements in and on the needles to be distinguished for an evaluation of the character of pollution.

Polarisation traps in a Si(Li)-detector

Time dependent background and artefacts in X-ray Fluorescence spectra have been studied with a fine X-ray beam close to the edge of the active area of a Si(Li) detector. The results indicate that polarisation takes place in this region of the detector under the influence of the bias. When the detector has been biased for several hours and is irradiated with photons in the 10-20 keV range the background decays with time constants in the order of 30 s and 1 h.

Use of total-reflection X-ray fluorescence in search of a biomonitor for environmental pollution in Vietnam

Abstract The concentration of trace elements in tissues of several animals collected in the Ha Nam province, approximately 40 km south of Hanoi, Vietnam, has been investigated using total-reflection X-ray fluorescence analysis. We find that the freshwater mussel is probably the optimal choice of biomonitor for the pollution situation in Vietnam, but the freshwater crab, the toad and the catfish are also good candidates. The krait is probably also well suited for this purpose. It is shown that since several elements show a more or less pronounced accumulation tendency in a particular tissue it can be of great use to determine the levels in different tissues. When selecting an organism to be used as a biomonitor, other factors besides the mere concentration of trace elements must be considered, for instance the abundance and feeding habits.

Mercury determination in environmental samples using EDXRF and CV-AAS

The determination of total Hg in various environmental matrices was investigated using energy-dispersive x-ray fluorescence (EDXRF) spectrometry on both powdered and digested samples and cold vapor atomic absorption spectrometry (CV-AAS) on digested samples. Several microwave decomposition procedures were evaluated. The use of different acid mixtures, microwave power settings and decomposition times were compared, in addition to the analysis of wet and freeze dried samples. A set of standard reference samples were used to evaluate the procedures. An H 2 SO 4 -HNO 3 -H 2 O 2 mixture was found to be optimal for the complete mineralization and digestion of biological samples for Hg by CV-AAS, whereas for EDXRF both HNO 3 -H 2 O 2 and H 2 SO 4 -HNO 3 -H 2 O 2 mixtures gave good results. The detection limit of EDXRF could be significantly decreased (from 0.2 μg g -1 to 0.058 μg g -1 ) by performing the analysis on digested samples. Good agreement was obtained between the EDXRF and CV-AAS analysis. The results were also in good agreement with certified values. The methods were applied to environmental samples (coal, vegetation, fish and sediment) and human hair in a coal mining area and in locations where coal is used for cooking in Vietnam.

Trace Element Analysis of Scots Pine and Norway Spruce Needles by Energy‐Dispersive X‐Ray Fluorescence Spectrometry

In recent years a new type of injury has been found on spruce trees in the southern part of Sweden. It starts with a flow of resin from the stem of the tree and within a relatively short time span the area close to the origin of the resinous flow dies. A few years after the first appearance of the injury the whole tree normally dies. The reasons for this phenomenon are not accurately known. The EDXRF method for analysing needle samples without chemical pretreatment of the samples was used in order to investigate the usefulness of the method for studying possible trace element anomalies in the bleeding trees. The concentrations reported are compared with results given by other analytical methods. Results from some preliminary measurements made on bleeding spruces are also presented.

Teaching environmental physics with a field measurement campaign

With 15 years of experience of teaching environmental physics, we still need to develop our curriculum. In this paper we present our findings from teaching environmental physics in close association with mathematical statistics in an applied field measurement campaign. Here not only environmental physics is taught, but also the concept of experimental planning, design, implementation, and evaluation of a field measurement campaign. The field measurement gives the students the opportunity to follow the whole process starting from experimental planning, including formulating the questions to answer, through design of the experiment, sample collection, analysis, and evaluation, together with the writing of a final report. All possible aspects of the problem that the students are working on can be carefully investigated, but the emphasis has been on understanding the whole process of carrying out a field campaign. This holistic view gives the students more interest in and better motivation for exploring the subject. This course gave the students insight into the field of interdisciplinary environmental research, promoted their creativity, and also gave the teachers a feeling of satisfaction.