Research A 200 Year Record of Atmospheric Cobalt, Chromium, Molybdenum, and Antimony in High Altitude Alpine Firn and Ice KATJA VAN DE VELDE, † CHRISTOPHE FERRARI, †,‡ CARLO BARBANTE, §, | IVO MORET, §, | TANIA BELLOMI, § SUNGMIN HONG, † AND CLAUDE BOUTRON* ,†, ⊥ Laboratoire de Glaciologie et Ge ´ophysique de l’Environnement du CNRS, 54 rue Molie `re, B.P. 96, 38402 Saint Martin d’He `res, France, Institut des Sciences et Techniques de Grenoble, Universite ´ Joseph Fourier de Grenoble, 28 Avenue Benoı ˆt Frachon, B.P. 53, 38041 Grenoble, France, Dipartim ento di Scienze Am bientali, Universita di Venezia, Dorsoduro 2137, 30123 Venezia, Italia, Centro di Studio sulla Chimica e le Tecnologie per l’Am biente-CNR, Dorsoduro 2137, 30123 Venezia, Italia, and Unite ´s de Form ation et de Recherche de Me ´canique et de Physique, Universite ´ Joseph Fourier de Grenoble (Institut Universitaire de France), B.P. 68, 38041 Grenoble, France High altitude cold snow and ice cores from midlatitude mountain ranges have been used very little to obtain historical records of environmental contamination by heavy metals. Co, Cr, Mo, and Sb have been measured by DF-ICP-MS- MCN (double focusing inductively coupled plasma mass spectrometry with microconcentric nebulizer) in various sections of a 140 m snow/ice core drilled at a high altitude location near the summit of Mont Blanc in the French- Italian Alps. The bottom of the core is older than 200 years. It gives the first snow and ice time series for these metals of high environmental interest for the post Industrial Revolution period. Measured concentrations range from 26 to 433 pg/g for Co, from 8 to 469 pg/g for Cr, from 0.2 to 50 pg/g for Mo, and from 0.2 to 109 pg/g for Sb. For all four metals, concentrations in recent snow are found to be, on the average, significantly higher than concentrations in ice dated from before the middle of the 19th century. There are however differences in the timing and the amplitude of the observed increases from one metal to another. Mo shows the greatest increase (×16), followed by Sb (×5), and Co and Cr (×2-3).Contribution from natural sources is, on the average, limited except for Mo in ice dated from before the middle of the 19th century. For recent snow, contribution from oil and coal combustion is the dominating source for Co, Mo, and Sb. For Cr, on the other hand, the most important contribution is from iron, steel, and ferro- alloy industries. 1. Introduction The study of the frozen archives which can be found in the Greenland and Antarctic ice caps has given a wealth of fascinatinginformation on the historyofthe composition of the atmosphere ofour planet (see, e.g. refs 1-5).Amongthe most interesting species to be studied are heavymetals such as Pb, Hg, and Cd. Investigation of the changes in the occurrence ofthese metals in dated snow and ice from central Greenland has for instance allowed for documenting early large scale pollution of the atmosphere of the northern hemisphere for Pb and Cu two millennia ago (6, 7) and the recent history of heavy metal pollution from the Industrial Revolution to present (see, e.g. refs 8-10). Interesting information was also obtained for the southern hemisphere from Antarctica (see, e.g. refs 11-14). On the other hand, very little effort was devoted toward decipheringthe historyofatmosphericheavymetalpollution on a regional scale in Europe or other temperate areas from the cold snow and ice fields which can be found in high altitude mountain ranges. To our knowledge, the only published data from such areas are for Pb, Cd, Cu, and Zn at a single location in the French -Italian Alps (15, 16). Until now most studies were devoted to Pb, Cd, Cu, and Zn and to a lesser extend Hg. Surprisingly, there are almost no data for other heavy metals such as Sb, As, Se, Cr, Mo, Ag, Au, Co, and V. Moreover, most of the very few published data for these last metals (see,e.g.refs 17-19)are considered to be unreliable because ofcontamination problems during field sampling and/or laboratory analysis (20). We present here comprehensive data on the changing occurrence ofCo (21), Cr (22), Mo (23), and Sb (24) in alpine snow and ice dated from the past two centuries.These metals are of high environmental interest since their atmospheric cycles are now significantly influenced by human activities (25), especially fossil fuel combustion, iron, steel, and ferro- alloyproduction and refuse incineration . Theywere obtained from the analysis ofvarious sections ofa snow/ice core drilled at a high altitude location in the Mont Blanc range at the French -Italian border.Analyses were performed byDF-ICP- MS-MCN (double focusinginductivelycoupled plasma mass spectrometry with microconcentric nebulizer). The data are discussed in the light ofavailable information on the different anthropogenic and naturalsources and their variation since the Industrial Revolution. 2. Experimental Section 2.1. Core Drilling and Dating. The samples were obtained as a 10 cm in diameter snow/ice core drilled at an altitude of 4250 m on the east slope of Do ˆme du Gou ˆter at about 1.5 km northwestofthesummitofMontBlanc (26).Thesampling site (45°50′N; 6°51′E) is characterized by a mean annual temperature of -11 °C and a mean annual snow accumula- tion rate of ∼3.5 m H2O‚yr -1 . The bedrock is ∼140 m below the surface.The close offdepth is ∼60 m. The core was drilled from the surface down to the bedrock using a stainless steel electromechanical drill coated with Teflon (PTFE). No wall retaining fluid was used. Great precautions were taken to minimize contamination brought to the outside of the core *Corresponding author phone: +33 476 82 4237; fax +33 476 82 4201; e-mail: boutron@glaciog.ujf-grenoble.fr. † Laboratoire de Glaciologie et Ge ´ophysique de l’Environnement du CNRS. ‡ Universite ´ Joseph Fourier de Grenoble. § Universita di Venezia. | Centro di Studio sulla Chimica e le Tecnologie per l’Ambiente- CNR. ⊥ Universite ´ Joseph Fourier de Grenoble (Institut Universitaire de France). 10.1021/es990066y CCC: $18.00  1999 American Chemical Society VOL. 33, NO. 20, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3495 Published on Web 09/14/1999