Anthropogenic sulfate and nitrate signals in snow from Bogda Glacier, eastern Tianshan

Abstract

A 1.2 m snow pit was recovered on July 29th, 2009 from the Bogda Glacier, eastern Tianshan (??). The sample site temperature of -9.6 ? indicates that the unique glaciochemical record was well preserved and suitable for the reconstruction of air pollution levels in this previously unexploredregion. Samples were analyzed for major ions (Na+, K+, Ca2+, Mg2+, NH4 +, Cl-, SO42-, NO3-,HCOO-, and CH3COO-). NO3 - and SO4 2- were characterized by significant high levels of pollution concentration. Most air masses backward trajectories ending in December 2008 have passed the Urumqi City center, while some even traveled across the primary nuclear weapons testing venue of the former Soviet Union (STS). The mean pH value of snow samples is coincident with the average value of Urumqi’s aerosol, and the ratio of [NO3-]/[SO4 2-] in the snow pit generally agrees with the value of the Urumqi winter aerosols. In addition, the [HCOO-]/[CH3COO-] ratio of snow samples is only 0.7, lower than unity. These analyses indicate that SO4 2- and NO3 -in the Bogda Glacier are the result of anthropogenic pollutions.