Pollution Characteristics And Sources Of Carbonaceous Component In PM_2.5 And PM₁₀ In Guanzhong Area

The air pollution in Guanzhong area is serious and the fog is frequent.It is the vital area for air pollution prevention and control.This study set sampling sites?XA,WN,TCH,BJ and XY?from September 2017 to January 2018 in five major cities in the Guanzhong area?Xi'an,Weinan,Tongchuan,Baoji and Xianyang?.Analysis of the temporal and spatial variation characteristics of PM_2.5.5 and PM₁₀0 of their carbon component concentrations,and the PMF model is used to analyze the source spectrum characteristics and backward trajectory cluster analysis of Xi'an.Scientific and effective data support for air pollution control in Guanzhong area.The results show that PM_2.5.5 and PM₁₀0 are highly correlated with manual and online monitoring concentration data,and the consistency is significant correlation,and the average value of manual monitoring samples is higher than online monitoring.The concentrations of PM_2.5.5 and PM₁₀0 in Guanzhong area were 87.39±46.54 and151.92±84.95?g·m^-3,respectively,mainly PM_2.5.The spatial distribution from high to low of particles with different particle sizes is basically the same as XY>XA>WN>BJ>TCH.The overall distribution is the most serious in the central part of Guanzhong,and the pollution in surrounding cities is relatively light.After the start of the heating season,the concentration of pollutants increased significantly,which was related to urban heating,lower boundary layer,more static and stable weather,and accumulation of pollutants.The sources of the two types of particles at each point are similar,but the difference between the sites is significant.The concentration of OC?Organic Carbon?and EC?Element Carbon?of PM_2.5particles in the atmosphere of autumn and winter in Guanzhong area ranged from 2.56to 42.36?g·m^-33 and 0.36 to 4.76?g·m^-33 respectively,3.10 to 61.44?g·m^-33 and 0.25 to7.07?g·m^-33 in PM₁₀,respectively.The spatial distribution of OC is the same as that of particulate matter,and the difference in EC is related to its source.The content of TCA?Total Carbon Aerosols?in PM_2.5.5 and PM₁₀0 was 31.86%and 22.70%,respectively.The seasonal distribution of OC and EC concentration and content was low in autumn and high in winter.The OC and EC of each site had the same pollution source and the different particles were mixed in the urban environment.The OC/EC ratio initially judges that the main sources of pollution contribution in Guanzhong are coal-fired pollution and motor vehicle pollution sources.The average concentrations of SOC?Secondary Organic Carbon?in PM_2.5.5 and PM₁₀0 were 7.44±5.54 and 9.62±7.49?g·m^-3,respectively.The content of SOC in PM_2.5.5 is 8.76%,accounting for 48.03%of OC,6.28%of PM₁₀,accounting for 48.09%of OC.The content in the fine particles is high.Seasonal distribution,winter is higher than autumn,and the formation conditions of winter SOC are more sufficient.Combined with the carbon composition characteristics of local pollution sources in Xi'an,the results of PMF model operation show that the pollution contribution sources of PM_2.5.5 carbon components are biomass combustion and coal combustion source?48.63%?,gasoline vehicle exhaust pollution?23.07%?,diesel Vehicle exhaust pollution?18.82%?,road dust pollution?9.47%?.XA,BJ and XY site biomass burning and coal source are the main contributors,while the TCH site is the main gasoline vehicle exhaust.The proportion of carbon source 4 pollution sources in PM₁₀0 particles was45.56%,23.78%,16.69%,and 13.97%,respectively.Compared with PM_2.5,the proportion of road dust pollution in PM₁₀0 particles is high.From the perspective of seasonal distribution,biomass burning and coal-fired sources change significantly in autumn and winter,with high winter and low autumn,especially BJ site The contribution of diesel exhaust is high in autumn and low in winter.Fine particles are most affected by biomass burning and coal-burning,gasoline-vehicle exhaust pollution.The results of backward trajectory clustering indicate that the Guanzhong area mainly has four trajectories from the northwest,west,northeast and local areas.The transmission of local area and the high concentration of PM_2.5.5 and PM₁₀0 in the northeast air mass are the main transmissions of polluted air mass.The XA and XY sites are closer to each other,and there is cross-contamination effect.The WN site is transported in the northeast direction,and the southwest direction is affected by the Weihua Group Plant emissions.The BJ site was accumulated by the transportation in the Guanzhong area.The geographical location of Guanzhong area is special,the surface wind speed is low,it depends on vertical mixed diffusion,the winter boundary layer is low,there is regional pollution transmission,and the difference between low air mass and perennial wind direction causes pollutant accumulation and SOC formation.In particular,the difference between the high and low pressure differences is not conducive to the spread of pollutants in the basin topography,so that the pollutants are paralyzed in the area,causing continuous pollution.In view of the pollution status of particulate matter and its carbon components in Guanzhong area,it proposes regional joint prevention and control,coal-fired technology innovation,improvement of vehicle use efficiency,use of clean energy,and targeted recommendations at various points.