Temporal changes in elemental composition in decomposing filamentous algae (Cladophora glomerata and Pilayella littoralis) determined with PIXE and PIGE.

Particle-induced X-ray emission and particle-induced gamma-ray emission spectrometry were successfully applied in a study of the elemental composition of decomposing filamentous algae. Fresh brown (Pilayella littoralis) and green (Cladophora glomerata) algal materials were placed in cages at 4m depth in a water column of 8m in the Archipelago Sea, northern Baltic Sea. Every second week decaying algae were sampled from the cages to allow measurements of changes in the elemental compositions. In the study of the elemental losses the concentrations were compensated for the mass reduction. The results show that sulphur, chlorine and partly potassium were lost during decomposition of P. littoralis and C. glomerata. Most of the other elements studied were recovered in the remaining algal mass. Special attention was paid to sorption and desorption of elements, including metal binding capacity, in the decaying algal materials. The affinity order of different cations to the two algal species was established by calculation of conditional distribution coefficients, D'(M). For instance for P. littoralis the following series of binding strength (affinity) of cations were obtained: Al>Ti>Fe >> Mn>Ni, Cu>Ba, Cr, Zn>>Rb>K, Sr>Pb>>Ca>>Na>Mg. Notably is that the binding strength of strontium was more than 10 times higher for P. littoralis than for C. glomerata. Due to their high binding capacity and good affinity and selectivity for heavy metal ions these algae have great potential as biological sorbents. Large variations in elemental content during decomposition complicate the use of algae for environmental monitoring.

Excitation functions of 3He- and alpha-particle induced nuclear reactions on natSb for production of medically relevant 123I and 124I radioisotopes.

Excitation functions were measured using the stacked foil irradiation technique from threshold energies to 28 MeV for (3)He- and to 21 MeV for alpha-particle induced nuclear reactions on natural antimony leading to the formation of (121,123,124)I radioisotopes. The measured excitation functions were compared with the contradicting results of the earlier investigations found in the literature and with the curves predicted by the ALICE-IPPE and EMPIRE-II codes. Integral yields were also calculated and compared with the experimental thick target yields reported in the literature.

Excitation functions of proton-induced reactions in (nat)Cu in the energy range 7-17 MeV.

Elemental production cross sections were measured for (p,x) reactions on natural Cu targets, leading to the formation of (62,63,65)Zn. These reactions are generally used for monitoring the proton beam intensity and energy e.g. in isotope production facilities. Cross sections were obtained by activation of stacked foils and subsequent gamma spectroscopy. The production data for (62,63,65)Zn between 7 and 16.5 MeV proton energy are presented as well as comparisons with literature values. Good agreement with the evaluated values was found for most of the cross-section values.

Elemental analyses of pine bark and wood in an environmental study.

Bark and wood samples were taken from the same individuals of Scots pine (Pinus sylvestris L.) from a polluted area close to a Cu-Ni smelter in Harjavalta and from some relatively unpolluted areas in western Finland. The samples were analysed by thick-target particle induced X-ray emission (PIXE) after preconcentration by dry ashing at 550 degrees C. The elemental contents of pine bark and wood were compared to study the impact of heavy metal pollution on pine trees. By comparison of the elemental contents in ashes of bark and wood, a normalisation was obtained. For the relatively clean areas, the ratios of the concentration in bark ash to the concentration in wood ash for different elements were close to 1. This means that the ashes of Scots Pine wood and bark have quite similar elemental composition. For the samples from the polluted area the mean concentration ratios for some heavy metals were elevated (13-28), reflecting the effect of direct atmospheric contamination. The metal contents in the ashes of pine bark and wood were also compared to recommendations for ashes to be recycled back to the forest environment. Bark from areas close to emission sources of heavy metal pollution should be considered with caution if aiming at recycling the ash. Burning of bark fuel of pine grown within 6 km of the Cu-Ni smelter is shown to generate ashes with high levels of Cu, Ni as well as Cd, As and Pb.

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.

A diagnostic study of proton-beam irradiated water targets.

A non-destructive method was developed for assessing the average density of a small-volume water target during particle beam irradiation. Due to local boiling of the target water the particle beam penetrates through the target and further through the thin back wall of the target unit. The charged particle beam excites water molecules both in the target water and in the cooling water. A light guide was inserted into the target cooling water to transfer the light emitted during de-excitation to a photodiode which produced a voltage signal when the beam entered the cooling water. Beam current and target-water temperature were recorded simultaneously with the diode voltage signal. The light emitted in the target during irradiation was photographed through a glass window on the target. Photographic views of the target medium during irradiation are presented. Formation of voids in the beam path of the target was verified with the photographic technique.

Preliminary biodistribution studies with a hybrid positron scanner.

The hybrid positron scanner is a scanning device for imaging with short-lived positron-emitting radioisotopes. It is especially suitable for total body scanning studies. The scanner consists of two moveable parallel detectors, which are NaI(Tl)-crystals 40 cm long and 5 cm in diameter with a photomultiplier at each end. One detector is above and the other below the patient. The coordinate in the direction perpendicular to the crystal axis is determined from mechanical movement of the detectors. The coordinate along the crystal axis is determined from the signals of the photomultipliers. The specifications of the hybrid positron scanner are presented. Biodistribution studies in rabbits on the accumulation of 18F in the skeleton and on the 13NH3 distribution in various organs are described. The regional pharmacokinetics of 11C-ethanol in man after peroral administration of the tracer is presented.

Transcapillary exchange and distribution of carbon-11 labelled ethanol in the isolated perfused rat liver.

The distribution kinetics of ethanol in the isolated perfused rat liver at various flow rates and ethanol concentrations were studied by the indicator diffusion technique using 11C-labelled ethanol. A double tracer solution with 99mTc-labelled red blood cells as the vascular reference and 11C-ethanol as the test substance was injected into the catheter connected to the portal vein. Time-activity curves were monitored by a NaI(Tl) scintillation detector above the outflow catheter. The following values were obtained: 0.95 +/- 0.01 for the maximal extraction (Emax), 3.0 +/- 0.1 x flow (r = 0.98) for the capillary permeability surface area product (PScap), 18.7 +/- 2.5% for the vascular volume (V1) and 56.2 +/- 9.0% for the ethanol distribution volume (V2). The volumes were calculated from the products of mean transit time (MTT) and flow (f), and PScap was calculated from the equation PScap = -f x ln(1-Emax). The results show that the ethanol distribution in the liver is flow limited since Emax was constant at various flow rates (0.67-2.55 ml/g x min-1). The distribution volumes obtained agree well with the values for liver vascular volume and water distribution volume reported in the literature.