Variations in heavy metal concentrations in the moss species Abietinella abietina (Hedw.) Fleisch. according to sampling time, within site variability and increase in biomass

Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mo, Ni, Pb, V and Zn were analysed in the moss Abietinella abietina (Hedw.) Fleisch. to estimate atmospheric heavy metal depositions. Samples were taken at five comparable sites within a radius of 25 m four times during the year 2000 (July 3rd, August 3rd, September 7th, October 3rd). The samples were taken by means of a PVC-tube (r=10 cm) and could therefore be related to aboveground growth and aerial deposition. The investigation showed significant differences between the various sampling times for concentrations of all heavy metals in total but not between concentrations of a single metal. For Cu, Hg, Mo, Pb and Zn temporal variation (=variation between the four times of sampling) was larger than spatial variation (=variation of concentrations between sub-samples at a single sampling time). Growth rates of the mosses differed significantly between sampling times, which reflects the low precipitation at the beginning of the season. Biomass increase, dust and precipitation influenced the metal concentrations. The calculation of deposition rates, which takes growth rates into account, showed significant differences between the various sampling times for Al, Cd, Cr, Cu and Ni, which is controversial to the results obtained from concentrations of these elements. Additionally, the calculation of atmospheric deposition rates showed a constant increase of metal depositions throughout the investigated period, which can not be seen by considering the concentrations only.