Research On The Regional Variations In Wintertime Physical And Chemical Properties Of Atmospheric Particles Over The East Edge Of Tibetan Plateau And The Sichuan Basin

Regional centers of maximum and minimum aerosol concentrations exist over the Sichuan Basin and its adjacent Tibetan Plateau in the spatial distribution.The spatial and temporal variations of atmospheric particles in the polluted and clean atmospheric environment between the two regions need to be analyzed,especially the physical and chemical properties of carbonaceous particles in the east edge of Tibetan Plateau and the Sichuan Basin,which is of great scientific significance for understanding the effect of atmospheric pollutants on the environmental changes of the Tibetan Plateau.In order to characterize the atmospheric pollutants and carbonaceous particle pollution in the east edge of Tibetan Plateau and the Sichuan Basin,this study conducted a statistical analysis of the air quality level and pollutant concentrations in January 2017 in the large city of basin,the small city of basin,the basin-plateau transitional zone,and the east edge of Tibetan Plateau zone;and this study divided the east edge of Tibetan Plateau and the Sichuan Basin into four areas:the urban zone of basin,the suburban zone of basin,the basin-plateau transitional zone,and the east edge of Tibetan Plateau zone,conducted the field measurement with day and nighttime membrane sampling of atmospheric particles in these four zones from January 1 to20,2017,and then investigated the carbonaceous components with the laboratory experiments.We further compared the difference in mass concentrations of carbonaceous particle in winter in the east edge of Tibetan Plateau and the Sichuan Basin,discussed the Spatiotemporal variations and size distribution characteristics of carbonaceous particle,and qualitatively analyzed the source of carbonaceous particle.The study results were concluded as follows:1.In the large and small city of the basin,as well as the basin-plateau transitional zone,the polluted weather prevailed in January 2017 with the polluted days of about 77.4%,77.4%,and 74.2%of the total days,respectively.The east edge of Tibetan Plateau was less polluted,with 96.8%of good air quality days.The large city of the basin was the most polluted,followed by the small city of the basin,and the plateau zone was the least polluted.In addition,the four zones of the east edge of Tibetan Plateau and the Sichuan Basin were ranked according to the concentrations of PM_2.5during the observation period:the suburban zone of basin(146.0?g?m^-3)>the urban zone of basin(127.1?g?m^-3)>the basin-plateau transitional zone(116.0?g?m^-3)>the east edge of plateau zone(42.8?g?m^-3).Even in the east edge of plateau zone with a clean atmospheric environment,ground PM_2.5and PM₁₀concentrations exceeded the national ambient air quality standards.And the over-standard rate of PM_2.5and PM₁₀in the basin zone was much higher than that in the plateau zone.During the heavily polluted period,the PM_2.5concentrations were highest in the large city of basin,and the pollution levels were similar in the four zone during the non-polluted period.The distribution characteristics of NO₂concentration showed:the large city of basin>the small city of basin>the basin-plateau transitional zone>the plateau zone.There is a period of NO₂pollution in the urban zone of basin,and its over-standard rate was 22.6%,indicating the impact of atmospheric pollution from urban transportation tail gas emissions in the Sichuan Basin.The concentrations of SO₂,CO,and O₃were small,and the pollution level meets the the national ambient air quality first-level standards.The concentration of SO₂in the plateau zone was greater than that in the basin.The order of CO concentrations showed the large city of basin>the basin-plateau transitional zone>the small city of basin>the plateau zone.The O₃concentrations in the plateau zone and the basin-plateau transitional zone were greater than those in the city of basin.2.Carbonaceous particles in the east edge of Tibetan Plateau and the Sichuan Basin were mainly concentrated in the size?2.5?m,followed by the 2.5?5?m.In the urban zone of basin,the suburban zone of basin,and the basin-plateau transitional zone,OC of the PM_2.5accounted for 76.31%,65.96%,and 81.90%of OC of the TSP,respectively,and EC of the PM_2.5accounted for 85.13%,90.20%,and 81.01%of EC of the TSP,respectively.This reveals that fine carbonaceous particle plays a leading role in atmospheric carbonaceous particle pollution in the east edge of Tibetan Plateau and the Sichuan Basin.In the particle size?2.5?m,the order of EC concentrations presented the suburban zone of basin>the urban zone of basin>the basin-plateau transitional zone>the plateau zone,with the order of OC concentrations in the urban zone of basin>the suburban zone of basin>the basin-plateau transitional zone>the plateau zone.And in the>2.5?m particle size,the distribution order of EC concentrations distributed with the urban zone of basin>the suburban zone of basin?the basin-plateau transitional zone with the order of OC concentrations in the suburban zone of basin>the urban zone of basin>the basin-plateau transitional zone.The concentrations of both OC and EC were higher in urban and suburban zone of the basin than in the plateau and the basin-plateau transitional zone.3.For the atmospheric particles with size?2.5?m,the main sources of carbonaceous particles were identified with coal combustion,and vehicle exhaust emissions in the urban zone of the basin;and was coal basin emissions in the suburbs zone of basin,the basin-plateau transitional zone,and the plateau zone,reflecting the effect of transportation differences between the urban and suburbs Sichuan Basin on different sources of carbonaceous particle.For the atmospheric particles with size>2.5?m,the main sources of carbonaceous particles were coal combustion and biomass combustion,and dust and household natural gas emissions in the urban zone of the basin and the basin-plateau transitional zone;and the carbonaceous particle was mainly affected by coal and biomass combustion,and cooking emissions in the suburbs zone of basin,where may be more affected by non-combustion sources than the urban zone of the basin and the basin-plateau transitional zone environments.In the urban and suburban zones of the basin and the basin-plateau transition area,the proportion of POC to TC was largest,the proportion of SOC was the second,and the proportion of EC was the smallest.In the plateau zone,the proportion of POC to TC was largest,and the proportion of EC was the smallest in fine particles.During the observation period,the east edge of Tibetan Plateau and the Sichuan Basin was mainly contributed by primary organic carbon,and the secondary organic carbon contributions in the basin zone was more than that those in the plateau zone,which could reflect the importance of the special warm and humid atmospheric conditions in the basin for the formation of secondary organic carbon.