The transport of chemical components in homogeneous snowpacks on Urumqi Glacier No.1, eastern Tianshan Mountains, Central Asia

Chemical records from alpine ice cores provide an invaluable source of paleoclimatic and environ- mental information. Not only the atmospheric chemical composition but also depositional and post-depositional processes are recorded within snow/tim strata. To interpret the environmental and climatic significance of ice core records, we studied the variability of glacier snowpack chemistry by investigating homogeneous snowpacks from October 2003 to September 2006 on Urumqi Glacier No. 1 in eastern Tianshan Mountains, Central Asia. Principle Component Analysis of ionic species in dry and wet seasons revealed the impact of meltwater in redistributing ions in the snowpacks. The 1st, 2nd and 3rd principle components for dry seasons differ significantly, reflecting complex associations between depositional or/and post-depositional processes. The variability trend of ionic concentrations during the wet seasons was found to fit a Gauss Function with significant parameters. The elution factor revealed that more than half of ions are leached out during the wet seasons. Differences with respect to ion snowpack mo- bility were found. Of the ions studied SO42- was the most mobile and Mg2＋ the least mobile. A threshold relationship between air temperatures and the elution process was investigated over the study period. The results indicate that the strong melt/ablation processes and iconic redistribution occur at a threshold air temperature of 0℃. The study found that surface melt on the snowpacks is the main factor causing the alteration of the snowpack chemistry. Rainfall also has an impact on the chemistry but plays a less significant role than the surface melt.

Anthropogenic Sulfate and Nitrate Signals in Snow from Bogda Glacier, Eastern Tianshan

A 1.2 m snow pit was recovered on July 29th, 2009 from the Bogda Glacier, eastern Tianshan （天山）. The sample site temperature of -9.6 12 indicates that the unique glaciochemical re- cord was well preserved and suitable for the reconstruction of air pollution levels in this previously un- explored region. Samples were analyzed for major ions （Na＋, K＋, Ca2＋, Mg2＋, NH4＋, Cl-, SO42-, NO3-, HCOO＇, and CHaCOO）. NO3 and SO42were characterized by significant high levels of pollution con- centration. 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-]/[SO42-] 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 SO42 and NO3in the Bogda Glacier are the result of anthropo- genic pollutions.