Study Of Chemical Composition And Sources Apportionment Of Atmospheric Particulates In Jiangnan District Of Nanning City In Winter

The historical data of particulate matter monitoring of two national environmental air quality monitoring stations in 21st Middle School and Shajing Middle School in Jiangnan District of Nanning City were analyzed.Three samples of atmospheric particulate matter from the Shajing Middle School site from December 26,2018 to January 22,2019 were collected.PM₁,PM_2.5.5 and PM₁₀,analyzed 9 kinds of water-soluble ions,16 kinds of inorganic elements,and OC and EC carbonaceous components.The orthogonal matrix factorization model PMF was used to analyze its source,combined with the analytical results and the country.The control station monitors the data online,and uses 3D high-energy laser scanning radar to analyze the temporal and spatial distribution characteristics of pollutants and the source of the 3 km range around the site.According to the online monitoring data,the concentrations of PM_2.5.5 and PM₁₀0 in the Jiangnan District of Nanning City decreased year by year from 2014to 2019,but the primary pollution was still dominated by particulate matter.The PM_2.5.5 pollution of both sites was heavier than PM₁₀,especially the PM_2.5.5 in Shajing Middle School is still higher than the national secondary standard and ranks the bottom in the eight air quality monitoring stations in Nanning.The seasonal distribution characteristics of particulate matter concentration generally showed winter>autumn>spring>summer,and the variation of day and night concentration was characterized by nighttime>daytime,and Shajing Middle School is more significant.During the monitoring period,the mass concentrations of PM₁,PM_2.5.5 and PM₁₀0 were 33.15,47.92 and 69.60?g·m^-3,respectively.The three daily trends were similar,and the correlation was significant and homologous.The concentrationorderofPM₁chemicalcomponentsis:OM>SO₄^2->NO₃^->NH₄⁺>mineral dust>EC>elements>other water-soluble inorganic ions;OM>SO₄^2->mineral dust>NO₃^->NH₄⁺>EC>Other water-soluble inorganicions>ElementsinPM_2.5;OM>mineral dust>SO₄^2->NO₃^->EC>NH₄⁺>Other water-soluble inorganic ions>Elements in PM₁₀.The secondary ions in the water-soluble ions are mainly composed of?NH₄?₂SO₄,followed by NH₄NO₃.The average values??of SOR and NOR in PM_2.5.5 are 0.39 and 0.06,respectively.The secondary transformation of sulfur element is obvious,and the nitrogen element is secondary.The conversion is not obvious,and the atmospheric particles carry more NH₄⁺,which is generally weakly alkaline.The higher concentration of inorganic elements includes Ca,Mg,Fe,Al and Pb.The other elements are low in content,and the heavy metal ions are mainly concentrated in the fine particles with the particle size<1?m,which is harmful to the human body.Through the OC and EC mass concentration,OC/EC ratio,8 carbon components in TC and SOC concentration,the source of carbonaceous components in Jiangnan District,including secondary conversion,is affected by tail gas emissions from diesel and gasoline vehicles and coal combustion.The three types of particulate matter are similar and the contribution ratios are different.The main source contribution rates of PM1 are:biomass combustion source?29.49%?>secondary source?27.65%?>motor vehicle source?18.67%?>coal source?12.48%?>dust source?11.72%?The main source contribution rate of PM_2.5.5 is:dust source?24.67%?>biomass burning source?22.59%?>motor vehicle source?20.33%?>secondary source?16.57%?>coal-burning source?15.84%?;the main source contribution rate of PM₁₀0 is:dust source?27.76%?>biomass burning source?23.52%?>secondary source?18.71%?>coal source?18.15%?)>Motor vehicle source?11.86%?.3D high energy laser radar scanning shows that the south side of the south railway station of the station,the main construction site?500 m storage construction project on the north side,1² km southwest side of the Moon Bay small courtyard and other construction sites?,the main road(800m South Station Avenue on the south side,The 500 m Sanjin Avenue on the east side and the 100m dike road on the north side are key areas for dust pollution,and pollution mainly occurs at night.Sanjin Avenue and South Station Avenue are the key control and control roads for motor vehicles.The extinction coefficient of the intersections of the two roads is obviously large,and the particulate matter is seriously polluted.The key area of biomass incineration is 200 m in the northwest of the station and 1.2 km in the northeast side of the farmland near Lipo.At higher temperatures,the ozone concentration is higher,and atmospheric oxidation significantly causes secondary conversion of particulate matter.Unfavorable meteorological factors such as high humidity and inversion,static stability,etc.can also lead to an increase in particulate matter concentration.