| The western Inner Mongolia is characterized by a widely desert distribution,intensity windblown sand activities and frequently storms,and is generally considered as an important dust transport corridor.The mineral sand produced by wind erosion land-surface that is be transmitted over a long distance to the east Asia,North America and other places,had a considerable impact on the atmospheric environment,human health,terrestrial ecosystems and geochemical recycling process.Despite the study about sandstorm and dust source had made a great progress,forming series of systematic,complete and quantitative research and monitoring method,and made outstanding achievements in dust source and dust transmission path in large scale,but meso-micro scale dust emission and transmission process in dust source understand unclear,little research have been reported.Desert as a global dust source,its internal sand release and transmission process is not only the key scientific issue for atmospheric environment and sand science,but also the uncertainty component model in earth system model,which become the hot spot and difficulty in global climate change study.So,we chose the western Inner Mongolia as a typical research area,and conducted series field monitoring and laboratory analysis on tectonic geomorphology,soil texture of land surface,land cover change,windblown sand/dust activity,wind energy environment,and wind erosion grain of spectral change,horizontal wind erosion flux and PM10 dust emission rates of the typical surface during windblown sand/dust processes,and also PM10 rare earth element content of the typical surface.The results show the main dust emission source and the potential dust transfer process in the study areas.The results of tectonic geomorphology,soil texture of land surface,land cover change,windblown sand/dust activity,and wind energy environment showed that desert had low dust emission capacity due to lower surface silt and clay fraction?silt fraction<10%,and clay fraction<5%?.However,the sand sea and neighboring areas contain multiple types of surfaces that release dust,such as dry lakes and riverbeds,degraded oases,and Gobi surfaces.?Silt fraction is 40%-65%,and clay fraction is 15%-43%?.This means that as a unique landform body under the influence of the dominant wind force,it is an important dust deposit area.A localized and seasonal sand/dust storm has released an abundance of fine dust particles from the surrounding area.These have been mixed and deposited in the Badain-jaran desert Tengger desert and also Mu us sand under the dominant wind force,and most particulate material are probably also reworked by the wind as the sand saltates and the dunes migrate.These variable winds homogenize the dust in this region by remobilizing it time and again.Since 2000,the rainfall areas that is more than 250mm is increasing rapidly in forest cover area,and reducing significantly in aeolian desertification,which not only help reduce the surface wind erosion,and strengthen the fallout process of dry/wet dust.The clay fraction is significantly accelerate the soil formation,and makes ecological restoration to the benign cycle in the dominant downwind area.Based on field observations and the determination of the fractions of aeolian dust on the land surface and in near-surface sand flows,we characterized the horizontal wind erosion flux of the land surface in the western Inner Mongolia areas of northern China,and the volume of dust emitted?PM10?during windblown sand/dust processes.The Alxa are exposed to frequent aeolian processes,but with a greater proportion of high-power events than the Mu Us sandy land.It can be seen that the marginal sand seas of the Desert(mean d:0.113 mm;mean Ir:37.01 kg day-1 m-2;QPM10:0.82 kg day-1 m-2),degraded land of oases of the inland rivers(mean d:0.073 mm mean Ir:17.21 kg day-1 m-2;QPM10:2.43 kg day-1 m-2),and Gobi-type deserts located in arid areas(mean d:0.102 mm;mean Ir:37.62 kg day-1m-2;QPM10:0.68 kg day-1m-2)are regions of strong Ir and sources of considerable dust emission.In contrast,the Mu Us sandy lands have both lower Ir(mean Ir:0.44 kg day-1 m-2)and PM10 dust emission rates(mean QPM10:0.04 kg day-1 m-2),and the larger suspended load particle size limit d?mean d:0.147 mm?because their surfaces have greater vegetation cover.Therefore,these areas also appear as poor sources of dust.Based on REE abundance data of land surface PM10 fraction,using the archon shale?PAAS?,the upper continental crust?UCC?and chondrite?CH?normalized processing,the normalized REE patterns,REE ratios and pairs REE rations land surface PM10 fractions are highly consistency.Homogeneous geochemical characteristics of PM10 fraction means that the same sources of PM10 fraction existed among whole study area.The results also suggest that?REE of the PM10fractions has obvious increasing trend along the dominant wind direction.The mean abundances of the REE elements in the degraded land of oases of the Ejin Qi and floodplains,marginal sand seas and gobi of the Badain jaran desert,marginal sand seas and gobi of the Tengger desert,and the Eastern Kobq desert and Mu Us sandy lands are 181.649?g·g–1,198.159?g·g–1,209.506?g·g-1 and 238.55?g·g-1,respectively.The REE geochemical characteristic of PM10 fraction in the space pasterns has high consistency with the monitoring results of wind erosion and dust release process.The lower?REE abundance of PM10 fraction usually located in the salt lake and oasis degraded land with high PM10 content and dust emission rates.Under the dominant wind force,abundant fine dust particles released from the surrounding area supply abundant fine particles for dust formation of the Badain jaran and Tengger sand sea surface during seasonal and localized windblown sand/dust activities,and also provide for storage of abundant amounts of the fine dust fraction.The REE abundance of PM10 fraction increased slightly on Badain jaran and Tengger sand sea and surrounding area,and increased significantly in the Mu Us sandy lands. |
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