Chemical composition of fresh snow in the Himalaya and Karakoram

The interpretation of firn and ice cores in high-altitude sites in central Asia requires a detailed knowledge of fresh-snow chemistry, especially in the extra-monsoon season. Since 1992 the Water Research Institute of CNR has been involved in sampling and analysis of wet and snow deposition in the Himalayan area. The first campaigns, which were based at the EV-K-2-CNR Pyramid site in Khumbu Valley, were focused on the southern side of the Everest group in monsoon season with the aim of evaluating the long-range transport of inorganic pollutants from the Indian subcontinent to the Himalayan range. In the following years, involving climbing expeditions, we extended our research to other regions outside the monsoon season. This approach allowed us to get a better knowledge of spatial and temporal distribution of major ions in snow deposition of the Himalayan region. Furthermore, our results show that nitrate and ammonium concentrations can be biased by post-depositional gas absorption. In fact the interpretation of nitrate values in glaciochemistry is rather difficult because nitrate concentrations in snow are affected by post-exchange with the atmosphere over a broad range of environmental conditions.