Oak leaves and pine needles as biomonitors of airborne trace elements pollution

With the aim of investigating their usefulness for biomonitoring atmospheric contamination, oak (Quercus robur) leaves and pine (Pinus pinaster) needles, were collected from 55 sampling points in rural areas throughout Galicia (NW Spain). Samples of terrestrial mosses, known to be good indicators of atmospheric deposition, were collected from the same sites, to allow comparisons to be made. The concentrations of Al, As, Cd, Cu, Cr, Fe, Hg, Mn, Ni, Ph and Zn in the samples were determined. The present study provides the first data on bioaccumulation in these tree species in rural areas, on a regional scale. The metal levels in the pairs of species, i.e. pine-moss and oak-moss, were compared; the corresponding correlations indicate that these tree species have a low capacity for monitoring air quality and also a limited efficiency as bioaccumulators of the metals studied. Despite the inefficiency of the tree species in reflecting atmospheric contamination in clean areas, the corresponding background levels of metals, essential for evaluating degrees of contamination, were calculated. Finally, some of the difficulties encountered in the use of the leaves and needles of these species in biomonitoring studies are reported. (C) 2003 Elsevier B.V. All rights reserved.