K.-E. Saarela

Environmental monitoring of trace elements in bark of Scots pine by thick-target PIXE

Bark samples were taken from Scots pines (Pinus sylvestris L.) from a polluted area near a metal plant and from a relatively non-polluted site. Thick-target particle-induced X-ray emission (PIXE) was used for the analyses after different types of prepreparation of the samples. The bark samples were analysed directly by radially scanning from inner to outer bark in order to study the variability of elemental concentrations in different layers. Some clear differences were found in the chemical composition of the inner and outer bark. The lowest detection limits for the analyses of heavy metal ions were obtained by combining dry ashing at 550 °C with the PIXE method. More than 100 times higher concentrations were found for the heavy metal ions Fe, Ni, Cu, Zn, Ga, As and Pb in the bark samples from a polluted area in comparison to samples from a non-polluted area. The work demonstrated that external-beam thick-target PIXE is a sensitive and reliable method for quantitative determination of heavy metals in tree bark samples.

Study of seasonal variations of trace-element concentrations within tree rings by thick-target PIXE analyses

Abstract Thick-target PIXE has been used for the quantitative determination of trace elements in annual growth rings of different tree species. A scanning device was developed for the remote control of the sample and a video-camera system for the exact monitoring of the spot to be analyzed. The samples were analyzed in steps of 1 mm. The widths of the tree rings studied were in the range 2.5–8.0 mm. Samples of Norway spruce and Scots pine were collected from Harjavalta, a polluted area in southwestern Finland. The elements studied were S, Cl, Br, K, Ca, Mn, Fe, Zn, Cu, Ni, Pb, Rb and Sr. Large variations were observed in elemental concentrations within individual tree rings. The highest concentrations for most elements were obtained for earlywood in the beginning of the growth season and the lowest values for latewood thus reflecting the biological activity. The method was calibrated using international standard reference materials. For most elements the matrix effects were found to be negligible. The detection limits for most metals studied were in the range 1–5 ppm.

Monitoring of chromium, copper and arsenic in contaminated soils using thick-target PIXE

Abstract Soil contamination by toxic metal ions is one of the most serious environmental problems today. In this work soil samples from an area where a wood preservation plant has been active were studied. Chromium, copper and arsenic (CCA) are the main metal ions used in preservation of lumber. For the monitoring of these metal ions and of other elements in soil, thick-target PIXE (TTPIXE) has been proved to be a successful method. About 20 elements were quantitatively determined in the soil samples from the contaminated area and from a reference area. The reliability of the results was evaluated by analysing geochemical certified reference materials (CRMs) of chemical compositions similar to the soil samples.

Thick-Target PIXE Analysis of Trace Elements in Wood Incoming to a Pulp Mill

Summary Trunk-wood samples of wood raw material incoming to a pulp mill were analysed by thick-target particle induced X-ray emission (PIXE). The tree species studied were pine and spruce from Finland, birch from Finland and Poland and eucalyptus from Uruguay. The wood samples were dry ashed to 550 °C prior to the analysis in order to increase the sensitivity of the method. The method was calibrated and validated using some wood based certified reference materials. The elements determined with the method were P, S, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Rb, Ba and F. The concentrations of the main elements P, S, K, Ca and Mn exceeded 50 ppm in most wood samples. The concentrations of heavy metal ions like Cu, Ni and Pb in the samples studied were below or close to 1 ppm. The ash content of birch, pine and spruce wood were in the range 0.2–0.4% and that of eucalyptus ca 0.5%.

Thick-target PIXE analysis of chromium, copper and arsenic impregnated lumber

Chromium, copper and arsenic (CCA) have for decades been used for wood preservation. Of these elements especially arsenic is very toxic. As CCA impregnated wood is still today used for many construction purposes, a monitoring of these metal ions is of great environmental importance. Thick-target PIXE is a powerful method for the determination of trace metals in wood. The TTPIXE method enabled study of variations of the elemental concentrations in lumber treated with CCA impregnation solution. Distribution patterns were obtained for both naturally occurring elements and elements introduced in the treatment process. During the impregnation process a desorption of e.g. alkali metal ions takes place from the wood. The sensitivity of the method is improved by dry ashing of the samples prior to PIXE analysis. The TTPIXE method was calibrated and validated using international certified reference materials (CRM) based on wood material. ” 1999 Published by Elsevier Science B.V. All rights reserved.

Thick-target PIGE analysis of plant materials preconcentrated by dry ashing

Plant materials were dry ashed at 550 degrees C and analysed using particle-induced prompt gamma-ray emission (PIGE). The analyses were performed with an external beam of 3 MeV protons incident on the target. Seven biological certified reference materials were analysed and used for the evaluation of the method for Na, Mg, Al, P and Mn. The elemental concentration to detection limit ratios were greatly enhanced by dry ashing of the biological materials. The concentrations of the elements in ashes were clearly above the values at which reliable analyses can be made. The method was applied to samples of spruce and pine. Due to the low ash content of the wood samples, the sensitivity of the method was radically improved. The detection limits for the five elements studied in spruce wood were in the range 0.014-2.5 mug g(-1). The set-up and the beam current used enabled simultaneous particle-induced X-ray emission spectrometry (PIXE) analyses, with the sensitivity optimised for heavier trace elements.

Ion Beam Analyses Of Bark And Wood In Environmental Studies

A large number of wood and bark samples have been analysed utilizing particle‐induced X‐ray emission (PIXE) and particle‐induced gamma‐ray emission (PIGE) techniques. Samples of common tree species like Scots Pine, Norway Spruce and birch were collected from a large number of sites in Southern and Southwestern Finland. Some of the samples were from a heavily polluted area in the vicinity of a copper‐nickel smelter. The samples were dry ashed at 550 °C for the removal of the organic matrix in order to increase the analytical sensitivity of the method. The sensitivity was enhanced by a factor of 50 for wood and slightly less for bark. The ashed samples were pressed into pellets and irradiated as thick targets with a millimetre‐sized proton beam. By including the ashing procedure in the method, the statistical dispersion due to elemental heterogeneities in wood material could be reduced. As a by‐product, information about the elemental composition of ashes was obtained. By comparing the concentration of an e...