Seasonal variations in the sources of natural and anthropogenic leaddeposited at the East Rongbuk Glacier in the high-altitude Himalayas

Abstract

Lead (Pb) isotopic compositions and concentrations, and barium(Ba) and indium(In) concentrations have been analysed at sub-annual resolution in three sections froma b110mice core dated to the 18th and 20th centuries, as well as snow pit samples dated to 2004/2005, recovered from the East Rongbuk Glacier in the high-altitude Himalayas. Ice core sections indicate that atmospheric chemistry prior to ~1953 was controlled by mineral dust inputs, with no discernible volcanic or anthropogenic contributions. Eighteenth century monsoon ice core chemistry is indicative of dominant contributions from local Himalayan sources;non-monsoon ice core chemistry is linked to contributions fromlocal (Himalayan), regional (Indian/Thar Desert) and long-range (North Africa, Central Asia) sources. Twentieth century monsoon and non-monsoon ice core data demonstrate similar seasonal sources of mineral dust, however with a transition to less-radiogenic isotopic signatures that suggests local and regional climate/environmental change. The snow pit record demonstrates natural and anthropogenic contributions during both seasons,with increased anthropogenic influence during non-monsoon times.Monsoon anthropogenic inputs are most likely sourced to South/South-East Asia and/or India, whereas non-monsoon anthropogenic inputs are most likely sourced to India and Central Asia.