Study On The Temporal And Spatial Variation Characteristics Of Dust Aerosols And Their Health Effects In The Area West Of The Hu Huanyong Line In China

The severe dust storm in northern China in spring 2021 drew new attention to dust pollution,which had gone unnoticed for many years.As one of the dust source areas on the west side of the Hu Line,the Tarim Basin has a unique basin topography that is complicating the source-sink relationship and transport process of dust aerosols in the basin.extremely complex.Furthermore,affected by global warming,northwest China has shown a trend of regional climate change,resulting in a certain increase in the vegetation coverage of the underlying surface.As the main inhalable dust aerosols,PM₁₀ has a significant impact on human health.Under the background of the increasing frequency of spring sandstorms in northern China in recent years,it is of great scientific significance to study the changes in the atmospheric environment,influencing factors and their impact on human health on the west side of the Hu Line in China.Therefore,this paper takes the Taklimakan Desert,the main high-incidence area of dust storms in China,as the central research area.It is based on multi-source observation data of environment meteorology and satellite remote sensing,as well as population health data for many years,combined with the WRF-Chem air quality model and health risk model,to understand the Hu Line in China in this century.The environmental significance of atmospheric aerosols was analyzed.The temporal and spatial changes of the atmospheric environment on the west side of the Hu Line and its influencing factors were investigated.The regional transport and emission of dust aerosols in the Taklimakan Desert was studied with exposure to health risks.The main conclusions are as follows:(1)The significance of the Hu Line to the geographical distribution of atmospheric aerosols in China and its environmental changesThe spatial distribution of the recent 20-year average aerosol optical depth(AOD)in China generally presents a spatial pattern of high in the eastern and low in the western.The Hu Line is basically the same as the boundary between natural aerosol emissions and man-made aerosol emissions in China.The seasonal average AOD reached its the highest value in spring,and autumn was the season with the lowest AOD.The changing distribution of aerosols in China's mainland is strongly influenced by the climate of East Asian monsoons.In July,in weak summer monsoon years compared with normal years,central and southern China showed relatively obvious positive anomalies of AOD,while northern and eastern coastal areas had negative AOD anomalies.Compared with 20a,the AOD in North China in El Ni(?)o years is 0.1–0.2 lower than that in 20a,while it is 0.1–0.2 higher in South China.The opposite is true in La Ni(?)a years,reflecting the impact of ENSO events on the interannual variability of winter aerosols in China.(2)Temporal and spatial evolution characteristics and influencing factors of dust aerosols on the west side of the Hu LineThe average number of sandstorm days in northern China had been fluctuating with a decreasing trend from 2000 to 2013,and increasing from 2013 to 2019.In the nearly 40 years,the high incidence season of sandstorm in Taklamakan Desert extended gradually from spring to summer.Since the beginning of this century,the range of sandstorm days in the whole Northwest China has shown an obviously downward trend.The spatial distribution of sandstorm days in northern China has been shrinking westwards since 2000,which has changed the spatial pattern of sandstorms in northern China.The temporal and spatial variations of sandstorm days in northern China is closely attributed to the decreases of average wind speed and gale days,the significant increase of annual precipitation and the increase of vegetation cover with the greenness and wetness of the land surface in northern China.The increase in near-surface wind speed in the southern margin of the Tarim Basin was an important meteorological factor for the frequent occurrence of sandstorms in this area,and the increase in surface vegetation coverage could be the main reason for the significant decrease in the sandstorms days in the Gobi Desert.(3)Regional transport and emissions of dust aerosols during a typical sandstorm in Taklimakan DesertUsing ground PM₁₀ observation data and ERA-5 meteorological reanalysis data,combined with WRF-Chem model simulation,a typical sandstorm process in the Taklimakan Desert in spring 2021 was analyzed,and the influence of soil moisture changes in the basin on sand and dust aerosols.Affected by atmospheric circulation,strong cold air invades the basin along three different paths.The cold air from the north crossed the Tianshan Mountains and produced a downdraft in the northern part of the basin,forming a ground dust layer.At the same time,the westerly belt in the south of the basin made the surface dust belt move eastward.The dust belt gathers at the northeast mouth of the basin,and the low pressure on the ground makes the dust layer rise to the free atmosphere above 7 km.The soil moisture of the underlying surface has different degrees of influence on the concentration and range of dust aerosols in the Taklimakan Desert.Compared to the sand-dust aerosol concentrations before and after the increase in soil moisture,dust aerosol concentrations in the central area decreased significantly with a negative rate of 2–10%to the western side of the basin and the central hinterland of the basin.(4)Health risk assessment of sand and dust aerosols emitted by deserts in Northwest China in springFrom 2017 to 2020,the average PM₁₀ concentrations in China showed a decreasing trend year by year on the time scale.In 2021,the PM₁₀ concentration in the North China Plain increased due to the strong sandstorm process in the south of Mongolia in spring.The number of premature deaths was related to PM₁₀ concentrations,premature mortality and mean population-weighted concentrations.In 2017,the excess deaths(NE)formed a belt-like pattern centered on the Beijing-Tianjin-Hebei region,radiating across the Northeast Plain,Eastern Sichuan,central China,and the Yangtze River Delta.After 2018,the scope of NE has shrunk to the Beijing-Tianjin-Hebei region year by year,and the number has also decreased significantly.In the spring of 2021,the scope and quantity of NE increased sharply,forming key high-value areas in the Beijing-Tianjin-Hebei region.Beijing(31,700),Tianjin(18,400),Shanghai(21,300)and Chongqing(21,400)topped the list of premature deaths.The emigration or inflow of the population has a two-way impact on air quality in different regions.