Impact of Po Valley emissions on the highest glacier of the Eastern European Alps
1National Research Council, Institute for the Dynamics of Environmental Processes (IDPA-CNR), Dorsoduro 2137, 30123 Venice, Italy
2Department of Environmental Sciences, University Ca' Foscari of Venice, Dorsoduro 2137, 30123 Venice, Italy
3Department of Land, Environment, Agriculture and Forests, Agripolis, University of Padua, Viale dell'Università 16, 35020 Legnaro, Italy
4School of Earth Sciences and Byrd Polar Research Center, The Ohio State University, 108 Scott Hall, 1090 Carmack Road, 43210 Columbus, USA
5Autonomous Province of Bolzano – South Tyrol, Department of Fire Control and Civil Protection, viale Drusio 116, 39100 Bolzano, Italy
6Earth Science Department, University of Pavia, Via Ferrata 1, 27100 Pavia, Italy
Abstract. In June 2009, we conducted the first extensive glaciological survey of Alto dell'Ortles, the uppermost glacier of Mt. Ortles (3905 m a.s.l.), the highest summit of the Eastern European Alps. This section of the Alps is located in a rain shadow and is characterized by the lowest precipitation rate in the entire Alpine arc. Mt. Ortles offers a unique opportunity to test deposition mechanisms of chemical species that until now were studied only in the climatically-different western sector. We analyzed snow samples collected on Alto dell'Ortles from a 4.5 m snow-pit at 3830 m a.s.l., and we determined a large suite of trace elements and ionic compounds that comprise the atmospheric deposition over the past two years.
Trace element concentrations measured in snow samples are extremely low with mean concentrations at pg g−1 levels. Only Al and Fe present median values of 1.8 and 3.3 ng g−1, with maximum concentrations of 21 and 25 ng g−1. The median crustal enrichment factor (EFc) values for Be, Rb, Sr, Ba, U, Li, Al, Ca, Cr, Mn, Fe, Co, Ga and V are lower than 10 suggesting that these elements originated mainly from soil and mineral aerosol. EFc higher than 100 are reported for Zn (118), Ag (135), Bi (185), Sb (401) and Cd (514), demonstrating the predominance of non-crustal depositions and suggesting an anthropogenic origin.
Our data show that the physical stratigraphy and the chemical signals of several species were well preserved in the uppermost snow of the Alto dell'Ortles glacier. A clear seasonality emerges from the data as the summer snow is more affected by anthropogenic and marine contributions while the winter aerosol flux is dominated by crustal sources. For trace elements, the largest mean EFc seasonal variations are displayed by V (with a factor of 3.8), Sb (3.3), Cu (3.3), Pb (2.9), Bi (2.8), Cd (2.1), Zn (1.9), Ni (1.8), Ag (1.8), As (1.7) and Co (1.6).
When trace species ratios in local and Po Valley emissions are compared with those in Alto dell'Ortles snow, the deposition on Mt. Ortles is clearly linked with Po Valley summer emissions. Despite climatic differences between the Eastern and Western Alps, trace element ratios from Alto dell'Ortles are comparable with those obtained from high-altitude glaciers in the Western Alps, suggesting similar sources and transport processes at seasonal time scales in these two distinct areas. In particular, the large changes in trace element concentrations both in the Eastern and Western Alps appear to be more related to the regional vertical structure of the troposphere rather than the synoptic weather patterns.