Determination of Mn, Fe, and Cu in chemically-treated wood pulps by the XRF addition method.

A rapid X-ray fluorescence addition method has been developed for quantification of the technically most important metals in wood pulp matrix (Mn, Fe, and Cu). Pretreatment consisted of just two steps: first, acid was added to the sample to achieve homogeneous distribution of the metals; the pulp was then pressed lightly on to Mylar film. Total analysis time was less than 10 min. The concentration range investigated was up to 15 mg kg(-1) for Mn and up to 5 mg kg(-1) for Fe and Cu. Metal concentrations in Scandinavian pulps are not expected to exceed these amounts. The quantification limit was 2 mg kg(-1) for all three metals. The reproducibilities and repeatabilities were concentration-dependent and varied between 3 and 19% and between 1 and 17%, respectively. The squares of the linear correlation coefficients between measured intensity and added metal concentration were 0.994, 0.950, and 0.932 for Mn, Fe, and Cu, respectively.

Leaching of aluminium from aluminium dishes and packages.

A study was carried out of the leaching of aluminium from aluminium cooking vessels and packages. Very small or undetectable levels of aluminium leached from packaging materials into foodstuffs. In boiling tests with neutral porridge no migration of aluminium into the test matrix was observed from the pan. When boiling milk, the leaching of aluminium was 0.2-0.8 mg/kg. The aluminium content of tap water in aluminium pans when reaching boiling point was 0.54-4.3 mg/l and increased with increasing boiling time to 6.3-17 mg/l. Aluminium dissolved in foods based on acidic fruit juice rose to levels of 2.9-35 mg/kg when the foods were boiled in aluminium pans. Steaming of currant berries in an aluminium vessel gave aluminium concentrations of 19-77 mg/kg in the resulting juice. The highest aluminium concentration of 170 mg/kg was measured in rhubarb juice prepared in the steaming vessel. Aluminium dissolved in water to levels of 0.81-1.4 mg/l when heated for the first time in new coffee percolators. The aluminium concentration of water heated in older percolators was 0.09-0.78 mg/l.

Factors affecting trace-metal bioaccumulation in Finnish headwater lakes.

Fourteen unpolluted Finnish headwater lakes with pH values varying from 4.8 to 7.0 were studied for trace-metal concentrations in water, sediment, aquatic plants (Nuphar luteum L., Sparganium sp.), aquatic insect larvae (Limnophilus sp., Phryganea sp.) and fish (Esox lucius L., Perca fluviatilis L., Coregonus sp., Salvelinus fontinalis L., Salmo trutta L.). Trace-metal deposition was estimated by analysing the snowpack. Non-parametric correlation analysis was carried out between trace metal concentrations in biota and pH, ANC, TOC, CA + Mg concentration in water and a given metal concentration in water and sediment. Bioaccumulation of several trace metals increased with increasing acidity and decreasing ANC in water. This was especially true for Pb and Cd. Aquatic plants were, in general, the best indicator group concerning differences in trace-metal bioaccumulation in lakes with different acidity. There was some evidence that a higher concentration of TOC in water may reduce bioaccumulation of Pb, Cd and Zn in aquatic plants and fish. The copper concentration in sediment was the only background variable explaining Cu concentration in aquatic insects. Multivariate analysis of the whole background data gave comparable preliminary results. Over 80% of the trace metal concentrations in biota of different lakes was explained by the background variables. In general, elevated concentrations of most of these trace metals can be expected to occur in the biota of acidified low calcareous lakes.

The selenium content of edible mushrooms in Finland.

In this investigation the selenium contents of 142 mushroom samples were determined. The majority of the samples were wild Finnish mushroom species generally used for human consumption. The selenium contents of some cultivated mushrooms were also determined. In all, the material analyzed consisted of 38 different mushroom species. Selenium concentrations were assayed after modified wet and dry ashing, by atomic-absorption spectrometry using the hydride technique and the standard-addition procedure. The reliability of the method was tested with certified standard reference materials. The results of analysis obtained indicate that selenium contents vary considerably between different mushroom species. Of the species investigated, by far the highest selenium contents were found in Boletus edulis (mean 17 mg/kg dry weight). Other mushrooms having considerable selenium contents included Macrolepiota (5.0 mg/kg), wild Agaricus spp. (2.7 mg/kg), Gasteromycetes (1.9 mg/kg), Lactarius torminosus (1.9 mg/kg) and Marasmius oreades (1.6 mg/kg). The contents in these mushrooms are sufficient to provide an amount of selenium that is nutritionally significant in relation to the total daily intake of selenium of the Finnish population. Other edible mushrooms generally used in Finnland, e.g. species belonging to Cantharellaceae, Russula, Boletaceae (other than B. edulis) and Lactarius (other than L. torminosus) contained only small amounts of selenium. The importance of these mushrooms as a source of selenium is therefore marginal. The selenium content of Lactarius torminosus decreased by an average of 32% during the blanching necessary before consumption of these mushrooms.