The Characteristics of Atmospheric Aerosol at Aksu, an Asian Dust-Source Region of North-West China: A Summary of Observations over the Three Years from March 2001 to April 2004

Abstract

The observed maximum concentration of total suspended particles (TSP) was 5.2 mg m À3 during the dust event of April 2003. Variations in the TSP and PM 11 (particles smaller than 11 mm) show that high atmospheric concentrations were observed during dust events that occurred mainly in spring and summer. According to the meteorological observations, dust storms or blowing sand/dust occurred not only in spring, but also in summer and autumn, though floating dust occurred mainly in March and April. The frequency of dust events was consisted with the results of dry deposition.During spring and summer, the size-distribution of aerosols is unimodal with a maximum in the range 3.3-7.0 mm, while in winter the size-distribution shows a bimodal pattern with two peaks; at 3.3-7.0 mm for soil particles and 0.65-1.1 mm for anthropogenic particles. From the results of size distribution of soluble ion concentration, anthropogenic particles consist mainly of ammonium sulfate and ammonium nitrate, which result from coal combustion for heating during winter.Concerning chemical composition, aerosols from Aksu contain a significant amount of evaporate minerals such as calcium carbonate (calcite), sodium chloride (halite), and calcium sulfate (gypsum and anhydrite). These evaporates are common minerals in the saline soils which are widespread around observation site, and it is suggested that they are provided into atmosphere from the ground surface together with soil particles.Major element composition for aerosols in Aksu show a lower SiO 2 content and higher FeO, K 2 O and MgO content compared with that for the saline soils (j < 125 mm), the loess deposits in the Tarim Basin and Central Loess Plateau, and Taklimakan Desert sands (j < 125 mm). This suggests that minerals rich in Fe, K and Mg, such as clay minerals and mica, come selectively from the soil surface into the atmosphere as mineral aerosols. This is because their particle size is generally smaller than that of quartz, the main constituent minerals in the soil.

Wet and dry deposition of mineral dust particles in Japan: factors related to temporal variation and spatial distribution

“…Shifting the size fraction of dust particles is attributable to differences in settling velocity with size. For a dust event in March 2001, Mori et al (2003 reported aerodynamic mass size distributions sampled at Beijing, China, and at Yamaguchi, 1500 km downwind from Beijing, western Japan. Although the major peak of aerodynamic mass size distribution at Beijing was found at 4.7-7.0 µm, the peak in coarse mode at Yamaguchi was 3.3-4.7 µm.…”

“…Continuous multi-year data of deposition flux have been reported for dusts transported from desert areas such as central and eastern Asia (Inoue and Naruse, 1987;Yabuki et al, 2005;Hsu et al, 2009;Sun et al, 2003;Ta et al, 2004;Zhang et al, 1993), North America (Reheis, 2006), and the Middle East and Sahara (Ganor et al, 2003;Offer and Goossens, 2004;Pye, 1992;Nihlén et al, 1995;Loye-Pilot and Martin, 1996). Data of shorter (nearly 1 yr or event basis) periods have been reported much more (e.g.…”

Temporal variability of mineral dust concentrations over West Africa: analyses of a pluriannual monitoring from the AMMA Sahelian Dust Transect

“…In the framework of the ADEC Experiment (Aeolian Dust Experiment on Climate impact; Mikami, et al, 2002), PM 11 concentrations have been measured in the northern part of the Taklamakan desert from 2001 to 2004, by weighting filters collected with an Andersen-like cascade impactor (Yabuki et al, 2005). In Aksu, North of the Tarim Basin, the minimum daily PM 11 concentration ranges between 54 and 70 µg m −3 .…”

The Structure of the Dust Layer over the Taklimakan Deser during the Dust Storm in April 2002 as Observed Using a Depolarization Lidar

“…The Aksu Station is situated in an oasis, 80 km southeast of the Aksu city. The data of the routine meteorological observation, automated meteorological instruments and aerosol sampling in the experimental field were available (Yabuki et al 2005). The lidar observations were continuously conducted from April 11 to 21, 2002 except several power failures.…”