Seasonal variations of heavy metals in the 1960s Alpine ice: sources versus meteorological factors

We present here the first reliable data on the occurrence of Pb, Zn, Cu, Cd , Bi, Mn and Al in high altitude cold Alpine ice. They were obtained by ana lyzing with three different analytical techniques various sections of a 140 meter long ice core drilled near the summit of Mont Blanc at the French-It alian border. Special emphasis was given to the study of seasonal variation s in ice dated from 1960/61 and 1967/68, i.e, ice deposited just before and after the opening of the Mont Blanc road tunnel. For all the metals, conce ntrations vary by two orders of magnitude from summer to winter, with the h ighest concentrations being observed in summer. For ph, Zn, Cu, Cd and Bi, the lowest concentrations range from 0.1 pg/g (for Bi) to 50 pg/g (for Pb), i.e, values which are comparable to concentrations observed in central Gre enland. Anthropogenic inputs are dominant for Pb, Zn, Cd, and Bi while inpu ts from natural sources are important for Cu, Mn and Al. Both source and me teorological parameters are responsible for the heavy metal content of high altitude alpine ice. These metals mainly originate from Western European s ources as indicated by back air trajectories and emissions data for the dif ferent countries. The observed seasonal variations are however largely link ed with the changing vertical structure of the regional troposphere, which prevented the transfer of pollutants to higher altitudes in winter but not in summer. Our data do not indicate a significant change linked with the op ening of the Mont Blanc tunnel. (C) 1998 Elsevier Science B.V. All rights r eserved.