The use of aquatic mosses in assessment of metal pollution: appraisal of type-specific background concentrations and inter-specific differences in metal accumulation

Tissue concentrations of Al, As, Cd, Cu, Fe, Pb and Zn were analysed from 73 river sites, including 29 unpolluted reference sites and 44 sites differently affected by land use and industrial and municipal waste waters. Concentrations were measured both in the youngest terminal parts (reflecting the most current exposure conditions) and in the whole vegetative shoot (indicating long-term exposure) of mosses. For the dominant moss species, Fontinalis antipyretica Hedw., the concentration data were stratified according to the river type (small, medium, or large peatland or moraine land rivers) and assessed for background concentrations and patterns of concentration gradients and explored possibilities for setting criteria for environmental quality standards (EQSs). Further, we analysed species-specific differences in metal concentrations of F. antipyretica, Dichelyma falcatum (Hedw.) and Hygrohypnum ochraceum (Turn. ex Wils.). The background concentrations varied more or less according to the river type; in general, peatland rivers had higher concentration than moraine land rivers. The highest metal concentrations were found in rivers contaminated by acid sulphate soils. For most metals, concentrations in D. falcatum and H. ochraceum were higher than in F. antipyretica. Prerequisites for using mosses in pollution assessment and preliminary suggestions for defining EQSs are presented.