Chemistry of Supraglacial Ponds in the Debris-Covered Area of Lirung Glacier in Central Nepal Himalayas

摘要

Glacial meltwater samples were collected from 15 supraglacial ponds at elevations ranging between 3989 and 4292 m above sea level in the debris-covered area of Lirung glacier in central Nepal Himalayas, from November 2010 to October 2011 on a bimonthly basis. We examined elevation trends, and their control by seasonality, dominant geochemical processes, and seasonal dynamics in these supraglacial ponds. Concentration of some parameters showed a decreasing trend with elevation but with high variability and modulation by seasons, being more prevalent in the post-monsoon. Sulfate is the only parameter showing significant elevation trends regardless of the season, although the trend is also affected by the monsoon. The concentrations of major chemical solutes were highest during post-monsoon season and lower in the pre-monsoon and monsoon seasons, indicating influence of seasonality on dissolution, dilution, and hydrological processes. Contribution to chemical loads from marine aerosols to these pond water appeared to be minor except for sodium and magnesium. Chemical weathering of carbonate and silicate minerals fueled by dissolution of pyrite appeared as the dominant geochemical processes.