No abstract

A direct TXRF method for the determination of metal impurities by applying three different freshwater algae, viz., Chlorella keslerii, Synehococcus sp. and Cylindrospermopsis raciborskii, was developed. The applicability of the slurry sampling technique was confirmed by comparing the analytical results obtained with those obtained by total digestion of the algae. The concentration data showed an acceptable agreement for Cu, Fe, Mn and Zn. The calculated accumulation factors for the metals detected were highest for Chlorella keslerii.

Three silicon carbide powders having different grain size distributions were analyzed by total reflection X-ray fluorescence (TXRF) spectrometry with the application of slurry sampling. For the elements investigated (Fe, Ti, V, Cu, Ni, and Ca) the line-to-background ratios show a maximum value at a surface concentration of 12.5 μg/mm2. For the realization of this surface concentration, a 25-μL aqueous slurry with a concentration of 1% (m/V) and pH of 10 was dropped onto the hydrophobic quartz carrier plate. For quantification of the intensity data, gallium was added as an internal standard to the slurries. Under these experimental conditions, the analytical data of the fine-grained powders (80–90% of the powder particles were less than 1.5 μm) are in good agreement with concentrations determined in various laboratories by inductively coupled plasma atomic emission spectrometry (ICP-AES), ICPmass spectroscopy (MS), electrothermal vaporization- (ETV)-ICP-AES, slurry sampling graphite furnace atomic absorption spectroscopy (GF-AAS), and neutron activation methods. Powders with a mean grain size greater than 1.5 μm deviate much more from the reference data. Calculated limits of detection (LODs) range from 2 to 25 μg/g. The precision expressed as relative standard deviation (RSD) varies between 4 and 14% for Fe, Ti, and V, whose concentrations in the fine-grained silicon carbide samples exceed by a minimum of tenfold their limits of detection; however the precision is very poor for Cu (66.6%) and Ni (62.3%), which have concentrations near the limits of the detection.

There is little data on the mineralogy of carbonate pedofeatures in the calcareous soils in Hungary which belong to the European prairie ecodivision. The aim of the present study is to enrich these data.The mineralogical composition of the carbonate pedofeatures from characteristic profiles of the calcareous soils in Hungary was studied by X-ray diffractometry, thermal analysis, SEM combined with microanalysis, and stable isotope determination.Regarding carbonate minerals only aragonite, calcite (+magnesian calcite) and dolomite (+proto -dolomite) were identified in carbonate grains, skeletons and pedofeatures.The values relating, respectively, to stable isotope compositions (C 13 , O 18 ) of carbonates in chernozems and in salt-affected soils were in the same range as those for recent soils (latter data reported earlier). There were no considerable differences between the values for the carbonate nodules and tubules from the same horizons, nor were there significant variations between the values of the same pedofeatures from different horizons (BC-C) of the same profile. Thus it can be assumed that there were no considerable changes in conditions of formation.Tendencies were recognized in the changes of (i) carbonate mineral associations, (ii) the MgCO 3 content of calcites, (iii) the corrected decomposition temperatures, and (iv) the activation energies of carbonate thermal decompositions among the various substance-regimes of soils.Differences were found in substance-regimes types of soils rather than in soil types.

No abstract