Content and Localisation of Heavy Metals in Thalli of Hemerophilous Lichens

For the purpose of this work an epiphytic lichen species, Hypogymnia physodes (L.)NyL, was used. Thalli of the lichen were treated with solutions of nitrate salts of heavy metals, including Zn(NO3)2, Cu(NO3)2, Pb(NO3)2, and Cd(NO3)2. To simulate the acid rain impact, pH of the metal mixture was lowered to pH 4, using Na2S2O5. Content of heavy metals was determined after a standard UV mineralization method (water solution) and burning method (in temperature 450°Cthalli), using a Microcomputer Voltage-ammeter Analyser (MAW). After two months exposure of the lichen to the mixture of heavy metal nitrates it was ascertained that there was an increase of accumulation of Zn, Pb, Cu, and Cd in the thalli; a decrease of thalli pH caused increased uptake of toxic elements by the lichen; Pb and Cd remained mainly on the surface of the thalli and in the cell walls, whilst Zn and Cu penetrated to the protoplast.