FRESH SNOW CHEMISTRY FROM HIGH MOUNTAIN REGIONS IN CENTRAL HIMALAYAS

During 1997 summer, fresh snow samples were collected from the high elevation region (5400-7000 m) of Dasuopu Galcier on the northern slope of Mt. Xixabangma (28°33'N, 85°44'E). Compared with other remote regions in the world, major ion concentrations in fresh snow are very low during summer in Mt. Xixabangma, suggesting that the atmosphere is very clean and may represent background value for the middle/upper troposphere in the middle/low latitude area. During summer at Mt. Xixabangma the fresh snow chemistry is minimally influenced by anthropogenic pollutants as revealed by the snow pH (mean value of 6.0). Conductivity of fresh snow are low and constant. A multi regression curve of pH vs conductivity shows a strong correlation; snow pH is negatively correlated with conductivity when pH < 6.0, and positively correlated when pH > 6.0. This suggests that the dominant chemical species of snow are interchanging between acid anions (e.g.SO₄^2-,NO₃^-) and crustal cations.