Heavy metals in fresh snow collected at different altitudes in the Chamonix and Maurienne valleys, French Alps: initial results

The Chamonix and Maurienne valleys, French Alps, are major pathways for int ernational truck and automobile traffic in Western Europe since they give a ccess to the transalpine Mont Blanc and Frejus road tunnels. Moreover, the seasonal snow pack, which accumulates from autumn to spring in these two va lleys, is a major contributor to fresh water resources for a large number o f people, especially in large cities such as Geneva, Lyon and Grenoble. Dur ing winter 1998, we have collected a series of snow samples from two well-i dentified snowfall events at various altitudes ranging from 1150 to 3532 m on the sides of these two deep valleys. They were analysed for Li, B, Ti, V , Mn, Fe, Co, Cu, Zn, Mo, Pd, Ag, Cd, Sn, Sb, Pa, Pt, Au, Pb, Pi and U by d ouble focusing inductively coupled plasma mass spectrometry with micro conc entric nebulization (DF-ICP-MS-MCN). Ultraclean procedures were used for fi eld sampling and laboratory analysis.; The results show surprisingly law co ncentration values. With the exception of Li, B, Pd, Sn, Pt and Au, concent rations are found to decrease with increasing altitude. Crustal enrichment factors larger than +/- 10 times the mean crustal abundance are observed fo r Cu, Zn, Li, Mo, Pb, Ag, Pi, B, Sb, Sn, Cd, Au, Pt and Pd, strongly sugges ting contributions from non-crustal sources for these metals, especially lo cal and/or regional anthropogenic sources. Significant contributions are li kely to originate from truck and automobile traffic, electrometallurgical a nd electrochemical industries and municipal incinerators. These data provid e with a unique snapshot of the situation which prevailed in the two valley s before the disaster which occurred on 24 March 1999 in the tunnel of Mont Blanc, which resulted into a massive fall of the traffic in the Chamonix v alley and a parallel rise in the traffic in the Maurienne valley. (C) 2000 Elsevier Science Ltd. All rights reserved.