Yellow sand

This is an area of strong continental climate with dry and hot summer and severe winter with strong winds that transport dust at short and long distance, for instance yellow sand phenomenon in northwest China. During air transport these soil particles absorb numerous pollutants-carcinogens, like benzo(a)pyrene and heavy metals (Ni, Cd, Co, Zn, Pb, As) both from industrial emissions into the atmosphere and waste landfill sites. 

Box 1. Yellow sand formation and transport in Asia (after Jie Xuan, 1999, see Bashkin, 2002)... 

Yellow sand or gold powder. It is used in suns where it produces golden yellow rays. It is a reddish yellow sand mixed with... 

Han, Y.-J., Holsen, T.M., Hopke, P.K., Cheong, J.-P., Kim, H., Yi, S.-M., 2002. Identification of source locations for atmospheric dry deposition of heavy metals during yellow-sand events in Seoul, Korea in 1998 using hybrid receptor models. Atmos. Environ. 38, 5353-5361. 

Park, S.-U., In, H.-J., 2002. Simulation of long-range transport of acidic pollutants in East Asia during the Yellow Sand event. Atmos. Environ. 36, 4877 1893. 

Uno I., Amano H., Emori S., Kinoshita K., Matsui I., and Sugimoto N. (2001) Trans-Pacific yellow sand transport observed in April 1998 a numerical simulation. J. Geophys. Res. 106, 18331-18344. 

The smaller Cw values are also connected with water deficiency in Steppe and Desert ecosystems. However, the concentration of various chemical species in rainwater of background regions is higher that that in the Forest ecosystem belt. The major reason is the wind deflation of the soil s surface owing to lack of tree species and only a lean protective layer of grasses and half-shrubs. A large mass of soil particles becomes entrained into the air migration. The most characteristic example is connected with the Yellow sand phenomenon (see Box 7). 

But none of that mattered to the alchemist. He had already seen many people come and go, and the desert remained as it was. He had seen kings and beggars walking the desert sands. The dunes were changed constantly by the wind, yet these were the same sands he had known since he was a child. He always enjoyed seeing the happiness that the travelers experienced when, after weeks of yellow sand and blue sky, they first saw the green of the date palms. Maybe God created the desert so that man could appreciate the date trees, he thought. 

In Asia, the sources of particalates in urban air are both natural (Yellow sand phenomenon) and of anthropogenic origin. 

Figure 8. Average concentration of various elements in particulates during Yellow sand case in Seoul (Choi et al, 1998)...

Chemical composition of particulate matter from Yellow sand phenomenon was studied in Seoul in spring 1998. The mean total suspended particle (TSP) mass concentration in urban air was 98.9 /zg m with the maximum 264.8 /zg m and the minimum 23.9/zg m (Cho et al, 1998). The ratio of mean SPS mass concentration for Yellow sand cases to that for the non-Yellow sand was 1.50, showing that the SPM tends to be greater in Yellow sand periods. The mean ratio of particles with diameter less than 10 pm (PM 10) to the TSP was 0.69 during Yellow sand cases. 

Analysis of these data show that concentration of each chemical element was higher in TSP during Yellow sand cases than during non-Yellow sand cases by 2-3 orders. Most elements were indicated to have higher concentrations in coarse particles than in finer ones. This could be related both to the chemical composition of soil from the Gobi desert as the main source of coarse TSP and to the adsorption of heavy... 

Although the annual mean pHs do not differ sitewise, pH of individual precipitation showed a very large fluctuation, ranging from 3.4. to 8.0. Acidic precipitation appeared episodically about 4% of the precipitation events showed pH of less than 4.0. About 70% of the precipitation had a pH below 5.6 and can be considered as acid rains. On the other hand, about 2% of the precipitation events had pH above 7.0, suggesting strong inputs of alkaline species to rainwater in this region. The input of Yellow sand is one of the important alkaline sources that effect the rainwater chemistry over South Korea. 

Choi K.-C. and Chun E.-C., 1998. Yellow sand composition analyzed by PIXE method. In Proceedings of the 1st K-J 1ST International Symposium on Advanced Environmental Monitoring, September 11-13, 1998, Kwangju, Korea, 124-125. 

Kim K.-W., Kim S.-O., Son A.-J., Lee B.-T. and Ko I., 1999a. Chemical composition of Yellow Sand particles during 1999 Spring episode. In Proceedings of the 2nd International Symposium on Advanced Environmental Monitoring. KJIST, Kwangju, South Korea, 118-119. 

Besides, billions of tons of terrestrial materials are discharged aimually through rivers (including the Huanghe, Aprock, Han, Keum, and others), tens of million of tons of mineral dusts (otherwise known as yellow sand ) are deposited annually into surface seawaters from the atmosphere. It has been suggested that the atmospheric dust flux at the Yellow Sea may be comparable to the river input. The sea receives more than 60% of precipitation in the... 

We analyzed the desert dust samples (yellow sand samples) for carbon and nitrogen isotopic composition with and without HCl treatment (Table 2). Using isotopic mass balance equations as below, carbon isotopic ratios of removed carbon from the Chinese loess samples (S CRemoved c)... 

Table 2. Analytical results of standard yellow sand (Kosa) samples collected from Gunsu Province, China...

A colourless or white vitreous solid, SiOj, insoluble in water and soluble (by reaction) in hydrofluoric acid and in strong allcall m.p. 1713°C b.p. 2230°C. The following forms occur naturally cristoballte (cubic or tetragonal crystals r.d. 232) trldymlte (rhombic r.d. 2.26) quartz (hexagonal r.d. 2.63-2.66) lechatellerlte (r.d. 2.19). Quartz has two modifications a-quartz below 575°C and fi-quartz above 575°C above 870°C fi-quartz is slowly transformed to trldymlte and above 1470°C this is slowly converted to cristo-balite. Various forms of sillcon(IV) oxide occur widely in the earth s cmst yellow sand for example is quartz with iron(III) oxide impurities and flint is essentially amorphous silica. The gemstones amethyst, op, and rock crystal are also forms of quartz. 

The uptake of SO2 on soil dust has been interested in relating to the observational evidence that negative correlation is seen between the concentrations of SO2, and Saharan and Chinese dust (yellow sand) in the field measurement (Hanke et al. 2003), surface of mineral particles is in general coated by nss-S04 (Kojima et al. 2006), and positive correlation is seen between the concentration of nss-S04 and mineral particles in aerosols (Carmichael et al. 1996). The existence of the oxidation process oti aerosol surface in addition to the gas phase reaction and liquid phase oxidatirai in water droplets has also been suggested by Kasibhatla et al. (1997) since the overestimation of SO2 and underestimation of S04 is seen systematically in the comparison between the global model calculation and observation. 

---