Studies on the stability of mercury in fresh snow for the reconstruction of historical Hg concentrations from glacial ice

Abstract
Glaciers are well suited as paleoclimate archives of natural and anthropogenic emissions. In order to reconstruct air pollution levels in the Altai region, a 140 m ice core was drilled at the Belukha glacier (49°48'26. 3"N, 86°34'42.8"E, 4062 m asl) in July 2001. The Altai Mountain range is located close to major sources of air pollution such as heavy metal mining and metallurgy in East Kazakhstan and the large Hg mine in Aktach, South Siberia. Preliminary results showed that the Belukha glacier might be a suitable paleoclimate archive. However, especially in the case of Hg, it is still unclear whether the deposition record contained in glacial firn and ice indeed reflects atmospheric concentrations. A study by Lalonde et al. [2002] suggests that Hg in fresh surface snow is not stable, but decomposes or re-enters the atmosphere. We therefore investigate Hg concentrations in freshly fallen snow at the high-alpine site Jungfraujoch, which is located at 3500 m asl in the Swiss Alps. Preliminary results show that Hg concentrations levels in pressent da clean winter snow at this site are of the same order of magnitude than at the Belukha glacier (low ng L ^-1 range). Sample preparation is conducted under class 100 clean room conditions according to ultra-clean procedures [Boutron and Batifol, 1985, Boutron, 1990, Ferrari et al., 2000]. Hg analyses are performed by cold vapour inductively coupled plasma mass spectrometry (CV-ICP-MS) (Finnigan MAT, ELEMENT) [Klaue and Blum, 1999].