Search

Abstract: A total of sixty-three surface snow samples collected at Urumqi Glacier No. 1 (UG1), Eastern Tien Shan between March 2006 and December 2007 were analyzed for the concentrations of Na, K, Mg, and Ca in the dissolved and insoluble fractions by ion chromatography (IC) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. The dissolved and insoluble concentrations of these four major elements showed significantly positive correlation (coefficients 0.7~1.0, p <0.0001) with the concentration of insoluble Al (a reference element of the upper continental crust), suggesting that the four elements were mainly derived from crustal materials. The median dissolved fraction percentage (DFP, calculated as dissolved/(dissolved+insoluble)×100%) was 67.1% and 35.7% for Ca and Na, respectively, but only 16.8% and 8.9% for Mg and K, respectively. This suggests that Ca and Na were more readily released into the meltwater than were Mg and K from mineral dust in the UG1 snow. The elution sequence through the surface snow was determined to be Ca>Na>Mg>K by the change of DFP. The temporal variability of DFP was attributed to different processes, such as dry/wet deposition in the atmosphere and the post-depositional melting and elution in snow. The DFPs were relatively stable during the dry/cold season (December through March) due to predominantly dry deposition and infrequent elution, whereas they varied significantly during the wet/warm season (April through November) because DFP was modified by wet deposition (which will increase DFP) and the elution process (which will reduce DFP). Our results reveal that DFP can provide a new insight into the understanding and explanation of ice core records, and basic information for evaluating the impact of atmospheric dust on biogeochemical cycles. [Copyright &y& Elsevier]

Trace elements (TEs) in the insoluble particles of surface snow are less affected by melting processes and can be used as environmental proxies to reveal natural and anthropogenic emissions. Here the first comprehensive study of the 16 TEs (Al, As, Ba, Bi, Cr, Cu, Fe, Mn, Ni, Pb, Sn, Sr, Ti, U, V, and Zn) in insoluble particles (>0.45 μm) from surface snow samples collected at Urumqi Glacier No. 1 (UG1), Eastern Tien Shan, China, from February 2008 to January 2010 were presented. Results show that concentrations of most insoluble particulate TEs (TEs insol) in the snow were higher in summer while lower in winter, due to the increasing particle inputs and melting processes. The abundances of As, Cr, Cu, Ni, Pb, and Zn in some samples were higher than those in surrounding urban soils, which might due to these TEs have further anthropogenic input beyond the already contaminated re-suspended urban soil particles and TEs were mainly enriched in particles with small grain size. Based on enrichment factor (EF) and principal component analysis (PCA), our results suggest that eight TEs (Al, Fe, Ti, Ba, Mn, Sr, U, and V) mainly came from mineral dust, while the remaining eight TEs (As, Bi, Cr, Cu, Ni, Pb, Sn, and Zn) were affected by coal combustion, mining and smelting of non-ferrous metals, traffic emissions, and the steel industry. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model suggests that pollutants might originate from Xinjiang province, Kazakhstan, and Kyrgyzstan. Moreover, UG1 received more significant inputs of particle-bound pollutants in summer than in winter due to the stronger convection and the prevailing valley wind that transports pollutants from the city of Urumqi. Image 1 • Trace elements in insoluble particles (>0.45 μm) of snow were reported. • Abundances of As, Cr, Cu, Ni, Pb and Zn were higher in samples than in urban soils. • Pollutants were more easily transferred to UG1 in summer than in winter. Abundances of As, Cr, Cu, Ni, Pb, and Zn were higher in samples than in urban soils, as well as particle-bound pollutants were more easily transferred to UG1 in summer than in winter. [ABSTRACT FROM AUTHOR]

Abstract: 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 HYSPLIT model results suggest that the Westerlies, Arctic air masses and local winds are the main circulations for dust transport to Eastern Tien Shan. [ABSTRACT FROM AUTHOR]

Abstract: The Pamirs are situated in the inner part of the Asian continent, a region which plays a critical role in Asian dust emission and transport. This study measured the elemental composition of atmospheric dust aerosol samples collected during the period between July 2004 and April 2006 at Mt. Muztagata, Eastern Pamirs, at a high-altitude (38°17′N, 75°01′E, 4430m). The Muztagata aerosol samples show Ca/Al (∼0.7) and Fe/Al (∼0.7) ratios that are distinguishable from those from other sites. The La/Th ratios (averaging 2.30–2.36) and Th/U ratios (averaging 2.75–3.11) indicate typical eolian deposition. The dust aerosol samples have very similar rare earth element (REE) patterns, with relative enrichment of light REE, a slight depletion of heavy REE, and a strongly negative europium anomaly (δEu values averaging 0.65). The Muztagata dust shows homogeneity of composition during the sampling period, with minor variations due to seasonal effects and possible different air mass, suggesting the possibility of a well-mixed atmospheric background dust on a regional scale. The zonal Westerlies dominate and the longitude circulations are relatively very weak for dust transport dynamics in the Pamirs and Tien Shan regions. Our results demonstrate a distinct difference in elemental composition between dust over the Eastern Pamirs and that over Inilchek, Central Tien Shan, indicating that the Asian dust emission regions have great variations in their chemical properties, and provide a better constraint on the climatic impact of Asian dust. [Copyright &y& Elsevier]