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  • Author or Editor: L. Tobler x
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Abstract  

Individual samples of several sets of plants (lichens, tobacco, spruce needles, grass, botanical reference materials) show highly significant correlations of Al, Fe, Hf, La, Na, Th, Ti and V with Sc. These correlations result from the terrigenous part of aerosols deposited on and measured together with the plants. The composition of this contamination is almost uniform among the different plant sets and can be approximated by the composition of the upper continental crust. The mass of the terrigenous material ranges from <1 to >100 mg/g plant. Its presence is expected to lead to concentrations of the above and of other elements that deviate substantially from those of plants without contamination. This is proved by the comparison of two sets of spruce needles, one of which was measured without and the other after removal of the aerosol.

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Abstract  

Northeastern Atlantic sedimentary rare earth element (REE) (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) phase associations among CaCO3, authigenic and lithogenic material are estimated from total sediment REE, Al, Ca, Si, Mn and Co abundances using a linear correlation technique. Phase associations were also determined using a selective chemical leaching technique specific for CaCO3+exchangeable cation, easily reducible oxyhydroxide and residual material. Results suggest that 25–50% of the REE associated with the clay material are exchangeable cations and 20–35% of the total 3+REE and 4% of the total Ce reside in coatings on the CaCO3 tests.

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Abstract  

The aerosols adhering to one year old spruce needles are investigated as for the mass deposited and as for the chemical composition. The method for the isolation of the material is presented. 33 elements are determined by neutron activation analysis. Precision, accuracy, sampling error and variation over 14 sites at the interior of woods are discussed. Chemical composition is compared to local topsoil and to local aerosols collected on filters.

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Abstract  

La, Ce, Nd, Sm, Eu, Tb, Yb and Lu were determined in needles of age class 5 from 6 individual Norway spruce trees and in their soils. Measurements were done by neutron activation analysis with a group separation of the REE. Concentrations in spruce needles are among the lowest values reported for plant leaves. Concentrations show small variations between the soils, but large variations between the trees. The mean ratio plant/soil is about 5·10–3 forall REE except Ce. Needles have no Eu-anomaly and a strong negative Ce-anomaly with respect to the soil. In addition to the fractionation of the individual REE between trees and the soil, there is also a considerable fractionation between the trees.

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Abstract  

Rare earth elements are isolated as a group from neutron activated rock samples by a new radiochemical procedure based on extraction with thenoyltrifluoracetone/phenanthroline in CHCl3. The procedure consists of three extraction steps, obviates the use of anactive carriers and gives practically quantitative chemical yields, thereby avoiding fractionation of the individual rare earths. Details of the dissolution, chemical separations and counting procedure are given togther with an analysis of BCR-1.

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Abstract  

The Si determination with epithermal neutrons using the reaction28Si (n,p)28Al is described. Thermal neutrons are eliminated from the irradiation position with a BN-shield. Two first order interfering reactions with P and with Al necessitate appropriate corrections. The interfering reaction on Al is shown to depend heavily on the hydrogen (H) content of the sample, which therefore must be taken into account. The lower application range in plant samles is estimated to be 500 g g–1. Reproducibility is <5% in suitable cases, but not as good if the necessary corrections are large. The capacity is 25 samples per 8 h. The method is applied to 3 plant standards (rice, hay and pine needles) and to 47 samples of spruce needles. The applicability to different plant materials is mainly limited by their relative Al, P and Si concentrations. Literature values are use to find plant categories in which Si can be reasonably determined by instrumental epithermal neutron activation analysis (IENA).

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Abstract  

Samples of various types (spruce needles, blackberry leaves, soils, and soil extracts) have each been taken at 6 places from the same site. In addition, 4 whirls each from 2 spruce trees were sampled. Rare earth elements (REEs) were determined in these samples by neutron activation analysis with a chemical group separation. Variations between places were found to be small with soils and soil extracts, but large with plants. Variations between whirls were small. Plants neither reflected the soil nor the soil extract. Both plant species were dissimilar, but the logarithm of their ratio was a linear function of the atomic number of the REE. A negative Ce anomaly (with respect to soil) was found in both plant species.

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Abstract  

Forest Swiss soils from 39 locations sampled ad three depths each were extracted with a buffered solution of pH 4.65 containing EDTA. Nearly 30 elements were determined by instrumental neutron activation analysis in these extracts. The results obtained are discussed in terms of efficiency of the extractant, precision and accuracy. Summariszed results are presented for the quantities fractions of the elements extracted.

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Abstract  

Selenium nuclides are available from thermal neutron induced nuclear fission of 235U at the gas-jet facility at the Swiss spallation neutron source (SINQ) at Paul Scherrer Institute, Switzerland. The formation of stable selenium compounds, their transport yields using the gas-jet system and their relative thermal decomposition temperature were investigated under oxidizing and reducing conditions in the target chamber. Using O2, H2, CO, and propene as additional gases, the selenium isotopes are suggested to form H2SeO3, H2Se, COSe, and C3H6Se, respectively, with overall 84Se yields of 1.5%, 4.7%, 6.3%, and 21.9%, respectively. Adsorption enthalpy, vapour pressure, solubility and acidity data for these species were collected from the literature or estimated from other known thermochemical properties. Carrier free bromine isotopes (84Br, 86Br) in the form of HOBr were obtained by thermally decomposing H2SeO3 and retaining elemental Se under oxygen rich conditions on quartz at 400 K.

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