Do moss bags containing devitalized Sphagnum denticulatum reflect heavy metal concentrations in bulk deposition?

The trace elements contained in atmospheric deposition have long been of environmental and human health concern. The concentrations of trace elements in bulk deposition are usually monitored using traditional methods, which are often complemented by use of the simpler and less expensive moss bag technique. However, some theoretical aspects of the latter technique are still not well understood, such as the relationship between the levels of trace elements accumulated in moss and the concentrations of these in the atmosphere. In the present study, the correlation between the concentrations of trace elements (i.e., Cd, Cu, Hg, Pb and Zn) in devitalized moss bags (Sphagnum denticulatum) and bulk deposition was studied during 12 exposure periods at 21 sampling sites (SS) affected by different degrees of contamination. Most of the significant correlations involved Cd and to a lesser extent Cu and Zn; however, no significant correlations were found for Pb and Hg. The environmental conditions and particularly the abundance of precipitation are the main causes of the absence of correlations in some cases, presumably because of the loss of elements via washing. Thus, although the moss bag technique is a very useful and economical environmental tool, the limits of the method must always be borne in mind.