『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, 4430 m). 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.』
1. Introduction
2. Sampling and measurement
2.1. Aerosol and ice core sampling
2.2. Inductively coupled plasma-mass spectrometry (ICO-MS) analysis
3. Results
3.1. Major element ratios
3.2. Trace elements
3.3. Chondrite-normalized REE patterns and parameters
3.4. Ice core dust composition
4. Discussion
4.1. Composition of Muztagata aerosol/ice core samples
4.2. The major homogeneity and minor variation in element composition:
Implications for a possible regional atmospheric background dust
4.3. Complex and variable properties of Asian dust from different
emission regions
5. Conclusions
Acknowledgments
References