Abstract: Brown algae, which are good indicators for estuarine metal pollution, can advantageously be analysed by energy-dispersive X-ray fluorescence. The use of thin film samples and samples of intermediate thickness has several advantages over the conventional thick pellet procedure. A quite homogeneous thin target is prepared by suspending 15 mg of dried and ground seaweed powder in bi-distilled water and evaporating the slurry on a 10 cm2 Mylar foil held in a Teflon ring. The effective sample weight in the beam is calculated by a procedure based on the scatter peaks in the spectrum. Sensitivities are typically in the 215 ppm range. The coefficient of variation per analysis averaged over ten elements amounts to 10%. The natural concentration variation in seaweed specimens at one location is 13%. Samples from locations in the more polluted western Scheldt estuary yield significantly higher values for several elements, relative to the eastern Scheldt sites. Possible trace element variations between the top and base of plants, and between different seaweed specimens and sampling seasons, are discussed.

Abstract: An evaluation of the accuracy and suitability of the LachanceTraill algorithm using effective α-coefficients, and the De Jongh α approach for x-ray fluorescence analysis of borax glass beads prepared from geological material was performed. By using theoretical α-coefficients obtained from the same standard and calculated elemental intensities, the two algorithms were compared under identical conditions. When only the monitor standard is used, the LachanceTrail1 approach is found to be inferior to the De Jongh basic α method. If multi-standard calibration is performed for both approaches, the accuracies are almost identical and no significant difference is found in the results. The LachanceTraill algorithm has the advantage of being easier to implement on a minicomputer and, when used without standards, it is found to give results within a few percent of the true values, which is a useful indicator in the choice of appropriate standards for more accurate analytical work.

Abstract: The half-life of28Al was redetermined on aluminium samples of different origin. Three different counting techniques were applied. The availability of highly purified samples (up to 99.9999%), the use of very fast electronic counting equipment and a complete automatisation allowed a good precision to be obtained in the final result of 2.2405 min.

Abstract: Air particulate samples were collected at Chapiquiña near Arica (Chile) with a six-stage cascade impactor for about 17-day periods during a 31 month interval. Sixteen elements were determined by energy dispersive X-ray fluorescence analysis, and the elemental concentrations were subjected to principal factor analysis. The variability with time of the coarse particles was described by two factors both related to soil dispersion, whereas the fine particle variations could be explained by a third factor related to marine influence. Enrichment factors were compared with those obtained in other remote continental areas, in particular those of air particulate matter sampled at Chacaltaya, Bolivia. Results point to a negligible anthropogenic influence.

Abstract: A fast (25 min) non-destructive determination of silicon in steel by 14-MeV neutron activation is described. The 1.78-MeV 28Al activity, induced by the reaction 28Si(n,p)28Al, is counted on a NaI(Tl) detector. An oxygen flux monitor is used to normalise to the same neutron flux. Two methods are described to correct for the 56Mn activity (2.58 h), induced into the iron matrix via 56Fe(n,p)56Mn. Nuclear interferences of phosphorus and aluminium have been examined. Special attention has been paid to stainless steels. A sensitivity of 0.02 to 0.05% of silicon is obtained. The precision is 2 to 3% for steels containing above 1% silicon, and 7% for 0.1% of silicon.