Evaluation of contamination, by different elements, in terrestrial mosses

Evaluation was made of the degree to which samples of terrestrial mosses (S cleropodium purum and Hypnum cupressiforme) collected in Galicia (NW Spain) were contaminated by different elements. The concentrations of Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, S, Se, and Zn in the mosses were determined, then the contamination factors were calculated by dividin g each value by the corresponding background level of that element. To asse ss contamination using contamination factors (CFs), a scale was established that allowed categorization of sampling sites for each element determined. The proposed scale comprises six categories, ranging from CF values of les s than 1 (no contamination) to values of greater than 27 (extreme contamina tion). Finally, all available information was brought together and summariz ed in a contamination index. This index has the advantage that it takes int o account the toxicity of the elements and that can be used with an already existing scale of classification.