A comparison between two moss species used as transplants for airborne trace element biomonitoring in NE Italy

Transplants of the mosses Hypnum cupressiforme and Pseudoscleropodium purum used as active biomonitors of airborne trace elements were compared in a survey carried out at Trieste (NE Italy). Twelve elements were considered: Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Pb, Ti, V, Zn. Water-washed materials of H. cupressiforme and P. purum, collected in a remote area to prepare transplants, showed comparable content of all elements, excluding Pb. Transplants of P. purum showed a significantly higher accumulation of Al, Fe, Pb and Ti; higher levels of Cu and V were accumulated in H. cupressiforme. Losses of some elements occurred in some samples of both species; the most consistent losses regarded Cr and Mn. Accumulation data of Al, As, Cd, Hg, Zn found in the two transplanted sets were not correlated. Differences in element uptake in the two mosses are likely to depend mainly on morphology, and probably on the different forms of emission and deposition types of the elements. The two mosses showed an overall accordance in discriminating sites highly and scarcely affected by trace element depositions, although they accumulated some elements, in particular Hg and Zn, in different ways. P. purum proved to be a better accumulator than H. cupressiforme, showing similar or higher accumulation and lower loss of almost all elements, especially those related to particulate, dry depositions; H. cupressiforme could be effective in detecting large-scale patterns, related to wet depositions. These results indicate that these mosses cannot be used interchangeably for monitoring particular elements, and are able to provide complementary information on different, local and long-range deposition patterns.