Bjarne Jensen

Measurement of peak areas in energy-dispersive x-ray fluorescence spectrometry

Abstract An algorithm is outlined for the measurement of peak areas in spectra obtained by energy-dispersive x-ray fluorescence techniques. Each fluorescence line is assumed to be a pure Gaussian function. Initially, a calibration equation relating the full width at half maximum (FWHM) to the centre of the peak is set up. Then, in an unknown spectrum, the Gauss function parameters are found by a stepwise procedure making a non-linear minimization procedure redundant. First, the background is estimated and subtracted; then the peak centres are found, and the FWHM is given by the calibration equation, which relates FWHM to the position of the peak centre. Finally, the amplitudes are estimated from a set of linear equations. The reliability of the proposed algorithm was proved for a variety of samples. The method was compared with a non-linear x2 minimization routine. Quantitative analysis of two standard reference alloys was accurate. Below 20 keV, a suitable FWHM calibration is obtained from a set of Kα lines. Above 20 keV, a set of Kβ1,3 lines is recommended.

Software package for quantitative analysis of solid materials by energy-dispersive x-ray fluorescence spectrometry without absolute calibration

Abstract A software package for quantifying elements in solids from energy-dispersive x-ray fluorescence data is described. The algorithm is based on the fundamental parameter approach and facilitates the simultaneous determination of several elements at widely varying concentrations. The software comprises three programs. One program, for spectrometer control and data acquisition, resides in a dedicated microcomputer. The two other programs, for spectra deconvulution and data evaluation, reside in a larger central computer. On-line communication between the computers is feasible, and the system facilitates the implementation of new improved programs. The performance of the system was tested on standard reference materials, and satisfactory accuracy was obtained for up to 21 elements.

Spring Melt and the Redistribution of Organochlorine Pesticides in the Sea-Ice Environment: A Comparative Study between Arctic and Antarctic Regions

Complementary sampling of air, snow, sea-ice, and seawater for a range of organochlorine pesticides (OCPs) was undertaken through the early stages of respective spring sea-ice melting at coastal sites in northeast Greenland and eastern Antarctica to investigate OCP concentrations and redistribution during this time. Mean concentrations in seawater, sea-ice and snow were generally greater at the Arctic site. For example, α-HCH was found to have the largest concentrations of all analytes in Arctic seawater and sea-ice meltwater samples (224-253 and 34.7-48.2 pg·L-1 respectively compared to 1.0-1.3 and <0.63 pg·L-1 respectively for Antarctic samples). Differences in atmospheric samples were generally not as pronounced however. Findings suggest that sea-ice OCP burdens originate from both snow and seawater. The distribution profile between seawater and sea-ice showed a compound-dependency for Arctic samples not evident with those from the Antarctic, possibly due to full submersion of sea-ice at the former. Seasonal sea-ice melt processes may alter the exchange rates of selected OCPs between air and seawater, but are not expected to reverse their direction, which fugacity modeling indicates is volatilisation in the Arctic and net deposition in the Antarctic. These predictions are consistent with the limited current observations.

Investigation of two computerized procedures for energy-dispersive X-ray fluorescence spectrometry by the fundamental parameter approach

Abstract Both the computerized procedures investigated for x-ray fluorescence spectrometry exploit the fundamental parameter approach. Procedures 1 and 2 are without and with absolute calibration of the spectrometer, respectively. The basic fundamental parameter equations are shown and the equivalence with the notation of influence coefficients is demonstrated. The advantages and limitations of the two procedures are discussed. If the sample contains no appreciable fraction of light elements, procedure 1 is well suited for standardless quantitative calculations. Procedure 2 is not limited by this restriction, and its use may indicate if the qualitative elemental analysis is complete. Even in the case of incomplete qualitative analysis, procedure 2 gives usable quantitative results. Calibration inaccuracies with procedure 2 are easily tested by procedure 1, thus the two procedures complement each other.

Atmospheric Pollution Research on Greenland

Danish studies in the Arctic atmosphere were almost all carried out on Greenland. There were not any specific programmes within IPY but activities were performed in the framework of Arctic Monitoring and Assessment Programme (AMAP) Financed from Denmark by means from DANCEA. A long series of studies in other spheres than the atmosphere have also been carried out but they will not be described here as they are beyond the scope of this chapter.