Depositional characteristics of NH4+ on Ürümqi glacier No. 1, eastern Tien Shan, China

Abstract

Investigation into the depositional and post-depositional processes of atmospheric NH4+ on Ürümqi glacier No. 1 (UG1), China, was implemented within the Program for Glacier Processes Investigation (PGPI) campaign. Aerosol and surface snow samples were collected concurrently on a weekly basis from March 2004 to March 2005 in the UG1 accumulation zone at the headwaters of the Ürümqi river, eastern Tien Shan. All samples were analyzed for NH4+ and other chemical species. This paper investigates the seasonal variations of NH4+. A significant linear relationship (R2 = 0.70, N = 21, P < 0.01) between NH4+ concentrations in surface snow and aerosol was found during spring and summer, indicating that the warm-wet condition facilitates the air-snow exchange of NH4+. Humidity was found to be a significant meteorological factor influencing NH4+ in deposition in autumn and winter. The NH4+ concentration in aerosol clearly shows a trend similar to that in surface snow, suggesting that the variation of atmospheric NH4+ might have been preserved in the surface snow. The possible source of NH4+ is discussed in this paper.