A COMPARATIVE-ANALYSIS OF 3 METHODS FOR D ETERMINING THE ELEMENTAL COMPOSITION OF BRYOPHYTES

The elemental composition of 11 Bryophyte species, found on ten peatla nds in the Athabasca, Alberta, Canada, was analyzed by energy dispersi ve X-ray spectrometry. The results were compared to those obtained by mineralisation of the same samples using a mixture of concentrated aci ds (HNO3 + HClO4) and a microwave oven, followed by analyses with an i nductively coupled Argon plasma spectrophotometer (ICP-AES). Accumulat ions of Al, Ca, Cu, Fe, K, Na, Mg, Mn, P, Pb, S and Zn were measured i n six Sphagnum species and five other Bryophyte genera, as well as sur face water obtained from the sampled peatlands. Analyses of the water samples indicated that a broad spectrum of peatlands was sampled and t hat there were wide variations in elemental concentrations. Discrepanc ies between Na concentrations in the samples as determined by X-ray sp ectrometry and ICP-AES spectrophotometry indicated that concentrations of this element could not be accurately determined by either method. Mineralisation of the moss samples using an acid mixture produced larg e standard deviations between replicates for all elements, while resul ts for the other two methods showed much smaller deviations. With the exception of Mg and Pb, a comparison between results for all elements obtained by X-ray spectrometry and the acid mixture were much less acc urate than the comparison between X-ray spectrometry and mineralisatio n using a microwave oven. Total concentrations of Ca, Fe, K, Mn, P and Zn measured by X-ray fluorescence were very close to those obtained b y mineralisation of the samples using a microwave oven followed by ana lysis using an ICP-AES spectrophotometer (r2 > 0.9). Conversely, X-ray spectrometry could not accurately determine accumulations of those el ements that had maximum concentrations < 10mg.kg-1 or atomic numbers l ess-than-or-equal-to 16.