The influence of pH on trace element uptake by an alga (Scenedesmus pannonicus subsp. Berlin) and Fungus (Aureobasidium Pullulans)

Experiments were carried oud in order to obtain information on the uptake characteristics of metals in the algal and fungus components of lichens. The uptake of ¹¹⁵Cd, ⁶⁵Zn, ⁶⁴Cu, ¹⁴⁰La, ¹⁸⁷W, ⁷⁵Se, and ⁷⁶As in the alga Scenedesmus pannonicus, subsp. Berlin and the fungus Aureobasidium pullulans was determined during 11 days of incubation at pH 5 and pH 7. The results indicate different acid-sensitivity of the alga and the fungus. The metal uptake in the alga was generally faster at pH 7, in the fungus uptake rates were higher at pH 5. In both the alga and the fungus for different pH-values hardly any differences in ultimate metal levels could be observed for Cd²⁺, Zn²⁺, La³⁺, and SeO _inf3 ^sup2- . In algae, the ultimate levels of the accumulated anionic forms of W and As appeared to be independent of pH; in the fungi the ultimate W and As levels were higher at pH 5. No differences could be observed in the Zn²⁺ accumulation capacities of both organisms. The As accumulation capacity of the alga was estimated to be about 10 times the As uptake capacity of the fungus. The results indicate the component-specific uptake and accumulatiom behaviour in intact lichens.     

Moss interspecies comparisons in trace element concentrations

Within the framework of a European-scaled moss survey, various moss species were sampled throughout The Netherlands [NL], Germany [D], and Switserland [CH], and used in moss interspecies comparisons of elemental concentrations. Moss species considered were Pleurozium schreberi [NL,D,CH], Brachythecium rutabulum [NL], Hypnum cupressiforme [D,CH], Hylocomium splendens [D,CH], and Scleropodium purum [D]. Element analysis was carried out directly (The Netherlands, Instrumental Neutron Activation Analysis: As, Br, Ce, Cr, Cs, Fe, La, Mn, Na, Rb, Sc, Se, Sm, Th, Ti, V and Zn), or after sample digestion (The Netherlands, ICP-MS: Pb, Germany, AAS/ICP-AES: Cd, Cr, Cu, Fe, Ni, Pb, Ti, V, and Zn; Switzerland, ICP-AES/ICP-MS: Co, V, and Zn).Local variations (=within sampling sites) in element concentrations were estimated, based upon in-site multiple sampling and analysis of Pleurozium schreberi species in The Netherlands. Element concentrations in moss species were compared in linear correlations, both in unweighted and weighted fits, with weighing factors based on the local variation data. Weighted fits were shown to generally improve the calibration characteristics, as tracked by X ² calculations.The calibration data suggest the presence of previously unnoticed outliers in element concentrations. The absence of further information, however, may prescribe the use of all data in comparison procedures. These results indicate that interlaboratory analysis of replicate samples and the use of dedicated certified reference materials may help solving problems in the analysis of the sample series.For several of the considered interspecies comparisons, weighted calibrations could be based on significant correlations (P=0.05). Actual use, however, will remain arbitrarily decided upon, and may be based on decisions as to what to accept with respect to the levels of uncertainty in the calibration parameters. Furthermore, the use of calibrations in extrapolation modes is greatly restricted by the necessary reservations in geographically larger-scaled applications.