| Based on the PM2.5 filter sampling data collected from the monitoring site of qiujing middle school in yuzhong district,chongqing,this paper carried out a chemical analysis of PM2.5 mass concentration,water-soluble ions,carbon components and inorganic elements to explore the characteristics of PM2.5 pollution in yuzhong district,chongqing.By using CMC method of chemical mass closure,the contribution rate of various chemical components in PM2.5 to PM2.5 concentration was demonstrated.The relationship between PM2.5 concentration and meteorological factors was analyzed,and the software SPSS was used for multiple linear regression analysis.Finally,the HYSPLIT trajectory model was used to simulate the backward trajectory of the pollutants at the sampling point of qiujing middle school in yuzhong district during the study period.The following conclusions are drawn:?1?during the spring sampling period in yuzhong district,chongqing,the PM2.5concentration ranged from 102.1-216.8?g/m3,with an average of 150.4?g/m3.During the autumn sampling period,the PM2.5 concentration ranged from 76.3 to 150.1?g/m3,with an average of 104.9?g/m3.The mass concentration of PM2.5 in spring and autumn of 2018 is 2.0times and 1.4 times of the second-level standard of daily mean PM2.5 stipulated in the latest environmental air quality standard?GB3095-2012?.From the perspective of seasonal difference,the mass concentration of PM2.5 in spring is greater than that in autumn.?2?the average concentration of water-soluble ions in yuzhong district of chongqing in spring and autumn of 2018 was 41.44?g/m3 and 32.87?g/m3,respectively,accounting for27.55%and 31.33%of the total average concentration of PM2.5.SO42-,NO3-and NH4+are the most important water-soluble ions,which are collectively referred to as secondary inorganic ions?SNA?.The SNA concentration averages in spring and autumn are 33.94?g/m3 and27.10?g/m3 respectively,accounting for 81.89%and 82.46%of the total water-soluble ion concentration averages.During the sampling period,the daily mean values of SOR and NOR in spring and autumn were 0.18,0.12,0.21 and 0.15,respectively.Therefore,it can be concluded that sulfate and nitrate in atmospheric aerosols in yuzhong district,chongqing are secondary pollutants obtained through transformation.From SOR>NOR,it can be seen that the transformation rate of gaseous pollutant SO2 is greater than that of NO2,and the transformation rate of SO2 and NO2 in autumn is greater than that in spring.?3?the concentration of TC,OC and TCA in spring was higher than that in autumn,while EC concentration in spring was lower than that in autumn.The concentration of OC and EC in spring was 1.35 times and 0.92 times higher than that in autumn,respectively.The OC/EC ratio was mainly distributed in 2-5 in spring and 1.5-2.7 in autumn in yuzhong district,chongqing,indicating that PM2.5 in the atmosphere was mainly caused by vehicle exhaust emissions,and the OC/EC value at night was lower than that in the daytime,which confirmed that the secondary pollution in spring and daytime in yuzhong district,chongqing was more serious.SOC is an important component of OC and PM2.5,and the proportion of SOC in PM2.5 in autumn is higher than that in spring.OC1 in different temperature section,OC2,OC3,OC4,EC1 EC2,EC2 concentration difference age season carbon component is the main source of yuzhong district in chongqing road dust,vehicle exhaust,OC3,EC1 content is less than the autumn,spring OC4,OC2 content than the autumn,OC4 sunny days in a state of concentration than rainfall,EC1 sunny days in a state of concentration less than rainfall?more than spring,autumn precipitation yuzhong district are consistent with the results of the analysis?.?4?the most main of PM2.5 inorganic elements of Si,Al,K,Ca,Fe,Mg,such as the earth's crust element,element analysis age season accounted for the total of 99.41%and99.19%,crustal elements in measuring elements of yuzhong district is got for:spring>autumn,Si,Al,Ca,Fe,Mg,Ti the six elements are the main tectonic element,concentration is higher,age season in inorganic element,element content accounted for 85.77%and 84.13%.Mg and V elements from the soil,road dust or rock weathering,Ni elements from motor vehicle exhaust,Mn,Cu element from industrial emissions,Co,Sr elements from coal,K is characteristic of biomass burning release elements,Mo element from fuel combustion,zinc,Pb element from the steel refining process,garbage burning and motor vehicle tyre wear.?5?PM2.5 source analysis results in yuzhong district,chongqing:CMC method with chemical mass closure showed that the contribution rates of water-soluble ions,mineral dust,OM,EC and trace elements in autumn were generally higher than those in spring.In spring and autumn,the content of water-soluble ions and OM is the highest,while the content of trace elements is the lowest.Due to the unique climatic conditions in chongqing,there are a large number of sulfur oxides and nitrogen oxides in the atmosphere of yuzhong district.Spring average concentration is higher than the fall did not identify the other substances,due to the strong ablility quartz membrane filter,in the case of high temperature and low humidity,of VOCs and half-VOCs and inorganic gases have a certain adsorption,yuzhong district,chongqing spring temperature,lower humidity and less rainfall,autumn low temperature,high humidity,rainfall,spring and PM2.5 mass concentration higher than autumn.?6?in the spring of PM2.5 concentrations affect the largest is the wind speed,SO42-,NO3-,NH4+,OC,EC and MIN,SO42-,NO3-,NH4+,OC,EC and MIN is positively related to impact,wind speed are negative correlation,autumn is the greatest influence on PM2.5 concentrations of precipitation,wind speed,SO42-,OC and MIN,SO42-,OC and MIN is positive correlation,precipitation and wind speed are negatively affected.?7?based on the HYSPLIT trajectory model,the regional air pollution source in yuzhong district of chongqing can be accurately simulated at a height of 500m.When the altitude is500m,the air transmission track in spring and autumn is roughly transported from southeast to northwest,but the main pollution source is still from the main urban area of chongqing?including yuzhong district?. |
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