Water and snow chemistry of main ions and trace elements in the karst system of Monte Pelmo massif (Dolomites, Eastern Alps, Italy)

Abstract

Water and snow chemistry of a high-altitude karst environment, the Monte Pelmo massif in the Dolomites (Eastern Alps, Italy), was investigated by a multidisciplinary analytical approach using ‘clean’ trace-metal techniques. Main ions of environmental significance (F–, HCOO–, Cl–, NO2–, NO3–, SO42–, Na+, NH4+, K+, Ca2+, Mg2+, HCO3–) were analysed by high-performance ion chromatography (IC). Trace elements of natural (Li, B, Mn, Co, Cu, U) as well as anthropic (Cr, Ni, Zn, Pb) origin were investigated by inductively coupled plasma-mass spectrometry (ICP-MS). Analytical data on filtered samples indicated that snow chemistry is dominated by the dissolution of air-borne particulate matter, primarily red dust of Saharan origin, which appears to be a preferred vehicle of contaminant transportation. In water samples, dolomite weathering was the predominant chemical step in the presence of sulfate ions, leading to excess magnesium concentrations and to Mg:Ca ratios often exceeding unity. The combined use of ICP-MS for trace element determination and chemometric tools, such as principal component analysis (PCA) and cluster analysis (CA), provided evidence of the absence of local anthropic pollution sources, and the presence of divalent transition metal cations associated with gypsum deposits. Finally, the excess uranium content was found to be associated with karst waters, and it could possibly have been a ‘natural’ tracer to characterise deep circulations.