Concentration and composition of dust particles in surface snow at Urumqi Glacier No. 1, Eastern Tien Shan

摘要

Major, trace, and rare earth elements (REE) were determined by inductively coupled plasma-mass spectrometer (ICP-MS) for dust particles that were extracted from fresh surface snow samples collected weekly or biweekly between March 2006 and January 2008 at Urumqi Glacier No. 1 (UG1) in Eastern Tien Shan, Central Asia. The UG1 dust shows average Fe/Al ratios of 0.7, Ca/Al ratios of 0.35, La/Th ratios of 2.62, Th/U ratios of 3.31, an Eu anomaly of 0.63, and L/HREE ratios of 7.87. Seasonal variation is significant in dust concentration, but is not observed in dust composition, which remains rather uniform throughout the sampling period. The compositional homogeneity suggests that dust materials in UG1 are well mixed from their possible source areas. Fine materials from the Junggar Basin, and to a less extend from Tarim Basin, more closely resemble UG1 dust properties in their REE composition than do the local moraines, indicating that the dust in UG1 snow mainly comes from mid- to long-range source areas. The HYSPUT model results suggest that the Westerlies, Arctic air masses and local winds are the main circulations for dust transport to Eastern Tien Shan.