Long-range transport of giant particles in Asian dust identified by physical, mineralogical, and meteorological analysis

Abstract

Abstract. Giant particles transported over long distances are generally of limited concern in atmospheric studies due to their low number concentrations in mineral dust and possible local origin. However, they can play an important role in regional circulation of earth materials due to their enormous volume concentration. Asian dust laden with giant particles was observed in Korea on 31 March 2012, after a migration of about 2000 km across the Yellow Sea from the Gobi Desert. Scanning electron microscopy (SEM) revealed that 20 % of the particles exceeded 10 µm in equivalent sphere diameter, with a maximum of 60 µm. The median diameter from the number distribution was 5.7 µm, which was larger than the diameters recorded of 2.5 and 2.9 µm in Asian dust storms in 2010 and 2011, respectively, and was consistent with independent optical particle counter data. Giant particles (> 10 µm) contributed about 89 % of the volume of the dust in the 2012 storm. Illite-smectite series clay minerals were the major mineral group followed by quartz, plagioclase, K-feldspar, and calcite. The total phyllosilicate content was ∼52 %. The direct long-range transport of giant particles was confirmed by calcite nanofibers closely associated with clays in a submicron scale identified by high-resolution SEM and transmission electron microscopy. Since giant particles consisted of clay agglomerates and clay-coated quartz, feldspars, and micas, the mineral composition varied little throughout the fine (< 5 µm), coarse (5-10 µm), giant-S (10-20 µm), and giant-L (> 20 µm) size bins. Analysis of the synoptic conditions of the 2012 dust event and its migration indicated that the mid-tropospheric strong wind belt directly stretching to Korea induced rapid transport of the dust, delivering giant particles. Giant dust particles with high settling velocity would be the major input into the terrestrial and marine sedimentary and ecological systems of East Asia and the western Pacific. Analysis of ancient aeolian deposits in Korea suggested the common deposition of giant particles from Asian dust through the late Quaternary Period. The roles of giant particles should be reviewed with regard to regional circulation of mineral particles and nutrients.

In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013

“…However, there is evidence of Aeolian dust transport and sedimentation of giant dust particles in the ocean up to 10 000 km away from source regions in the tropical Atlantic (Prospero et al, 1970;Carder et al, 1986) and Pacific (e.g. Betzer et al, 1988;Middleton et al, 2001;Jeong et al, 2014). Airborne observations also confirmed that the coarsest particles (> 20 µm in diameter) are far from completely depleted over the North Atlantic (McConnell et al, 2008;Ryder et al, 2013).…”

An Evaluation of the CHIMERE Chemistry Transport Model to Simulate Dust Outbreaks across the Northern Hemisphere in March 2014

“…Nevertheless, in this version of CHIMERE the formation of coarse nitrate due to the reaction of calcium with nitric acid (issued from the anthropogenic pollution) is not considered and could enhance the interactions between natural and anthropogenic emissions as it has been studied in China [101]. The transport of "giant" mineral particles, which can be defined as particles with diameters exceeding 10 µm, is rarely documented in the literature according to a recent study [102]. This study analyzes a specific Asian episode leading to the delivery of big particles in Korea thanks to mid-tropospheric strong winds.…”

The environmental implications for dust in high-alpine snow and ice cores in Asian mountains

“…Asian dust in Mt. Tateyama (central Japan) snow samples show a median volume diameter 6-21 μm (Osada et al, 2004), while dust particles of up to 60 μm (equivalent sphere diameter) have been transported as far as 2000 km away (Jeong et al, 2013). Therefore, transport of large particles from the remote arid region to the high-alpine glacier surface on the Tibetan Plateau is feasible.…”