Abstract:

As an important hub city of the "Silk Road Economic Belt"， Xi'an is located in the Guanzhong Basin， bordering the Loess Plateau to the north， Qinling Mountains to the south， and a large number of gobi desert distributed in the northwest， which is an important influence area of sand and dust transit in northern China. In order to study the variation characteristics and potential source areas of atmospheric particulate matter concentration on different time scales during Spring dust in Xi'an， this paper comprehensively analyzes the continuous monitoring data of ambient air quality in Xi'an from March to May 2023. The cluster analysis， potential source factor analysis （PSCF） and concentration weight trajectory analysis （CWT） of a typical dust process were carried out by using HYSPLIT backward trajectory model. The results show that： （1） In the Spring of 2023， there were 9 dust processes in Xi 'an， one of which was blowing sand and the rest was floating dust； The dust distribution was concentrated in March and April， showing a spatial pattern of more in the west and less in the east， more in the surrounding area and less in the city. （2） The concentration of atmospheric particulate matter presented significant response characteristics on different time scales. Specifically， the concentrations of PM₁₀ and PM_2.5 in the dust period were much higher than those in the non-dust period， and PM₁₀ was significantly higher than PM_2.5. The monthly variation of PM_2.5 and PM₁₀ concentration showed a fluctuating change characteristic of first increasing and then decreasing. The ratio of PM_2.5/PM₁₀ showed the characteristics of March > May > April， while the correlation between PM_2.5 and PM₁₀ showed the characteristics of March < May < April. （3） In the process of sand lifting from April 20 to 21， the concentration of PM₁₀ and PM_2.5 showed a "single-peak" type change， the PM_2.5/PM₁₀ ratio showed an inverted" U" pattern change. The concentrations of NO₂， SO₂ and CO all showed a decreasing trend， while the concentration of O₃ showed a decreasing trend first， then increasing and then decreasing. （4） From April 20 to 21， the dust process was formed by the transit of Mongolian High Pressure and surface cold front， and the sand transport path was northwest path， north path and east path. The dust sources were Tengger Desert， Badain Jaran Desert， Kubuchi Desert， Mu Us Desert， Gobi Desert in southern Mongolia and sandy land in northern Henan Province.

Key words: dust storm, ambient air quality, source, Spring, Xi'an