Testing differences in methods of preparing moss samples.

Various methods are currently used to prepare moss samples prior to their analysis in biomonitoring surveys. To date there has been no investigation of whether different results are obtained by using different preparation techniques. We therefore selected three preparation procedures (freezing, drying and acclimatization), currently applied in the European Moss Survey and other studies, to test whether significantly different concentrations of Al, As, Cd, Cr, Cu, Fe, Hg, K, Ni, Pb, Se, V and Zn are obtained. In addition, we considered the effect that the degree and type of contamination of the sampling sites and the different times of the year may have on the results. We found significant differences in the concentrations of all elements in the moss samples subjected to the different procedures and recommend standardization of the methods of sample preparation for valid comparison of the results. We further recommend that the samples are picked over directly in the field, to remove adhering material, and then cleaned prior to analysis.