Conifer needles as biomonitors of atmospheric heavy metal deposition: comparison with mosses and precipitation, role of the canopy

Concentrations of seven elements (As, Cd, Cr, Mn, Pb, V, Zn) in mosses (Hylocomium spledens, Pleurozium schreberi, Eurhynchium angustirete) and needles of Norway spruce (Picea abies) and juniper (Juniperus communis) were determined at 48 sites in Lithuania. Conifer needles consistently showed many times lower concentrations than mosses collected at the same site. Correlations between heavy-metal concentrations in needles and mosses indicated that accumulation processes may be similar, but mosses appear to be clearly preferable as biomonitors of atmospheric deposition because of their higher elemental concentrations and more quantitative reflection of deposition rates. Precipitation in the open field and under the canopy was investigated at two stations with respect to the same metals. The canopy was shown to retain a considerable part of lead, whereas elements such as Zn and Mn were enriched in precipitation under the canopy. Study of metal concentrations in moss growing, respectively, below and outside the canopy showed that none of so studied elements was significantly retained by the canopy. Most of the metals (Cu, Fe, Zn, Cr, Ni, V) were leached from the canopy to a smaller or greater extent. (C) 2000 Elsevier Science Ltd. All rights reserved.