关键词: 石英氧同位素, 沙漠, 沙地, 地表沉积物, 空间分布, 中国

Abstract: The widely distributed arid land in northwest China provides abundant dust for sandstorm occurrence,which causes the serious economic and social problems.It is important to monitor the change of environmental and meteorological factors and to study the desert ecosystem and desertification control.In recent years,some researchers found that dust play a positive effect on increasing the nutrient content of river and enriching the nutrient content of topsoil.So the study on provenances of aeolian sand is of not only the great theoretical and practical significance in aeolian geomorphology,but is also essential for understanding the complex linkages among dust emission,loess accumulation,climate system,and ocean biogeochemistry cycle.It is generally known that the dust sources in China are mainly the vast deserts and sandy lands in northwest China,but the specific distribution and contribution rate are unclear.Previous researchers found that the isotopic exchange of sand-sized quartz was minor under sedimentary conditions.In other words,the isotopic features of quartz will not be changed even after a number of sedimentary cycles.So this paper studied the oxygen isotopic distribution of quartz to establish a foundation for dust tracing.In order to understand the oxygen isotopic distribution of quartz in the main deserts (sandy lands) in China,seventy-five sediment samples were collected from eight deserts and four sandy lands in China,including the Taklimakan Desert,Gurbantunggut Desert,Kumtag Desert,Qaidam Desert,Tengger Desert,Ulan Buh Desert,Mu Us Sandy Land,Hobq Desert,Badain Juran Desert,Hulunbuir Sandy Land,Otindag Sandy Land,and Horqin Sandy Land during the period from 2014 to 2016.Samples were taken from 10 cm thick topsoil far away from human habitation.The samples were crushed to pass through a 200 mesh.Oxygen isotopic compositions of quartz were measured by means of isotope ratio mass spectrometry.The result showed that the quartz δ¹⁸O values varied between 7.8‰ and 14.9‰.There was a big difference in homogenization degree of internal surface sediment among different deserts (sandy lands),in which the homogenization degree in the Taklimagan Desert was the lowest,and that in the Badain Juran Desert was the highest;the spatial variation of oxygen isotopic compositions of quartz in the main deserts (sandy lands) in China was obvious.

Key words: quartz oxygen isotope, desert, sandy land, surface sediment, spatial distribution, China