Pollution Characteristics And Sources Apportionment Of Atmospheric Particles In Laiwu City

In this paper,Laiwu City was selected as the study area,and atmospheric particles were used in 2016.For the four periods,atmospheric particles of three particle sizes(TSP,PM₁₀,and PM_2.5)were collected.Five samples of ambient air were sampled,and long-term online monitoring data were analyzed to obtain the main pollution characteristics of atmospheric particles.According to the nature of the pollution sources,soil dust,road dust,and urban dust were collected in different seasons,and samples of building cement dust,coal dust,and motor vehicle gas dust were collected only one time,and the characteristics were analyzed.The environmental receptor samples collected were tested to analyze the characteristics of the water-soluble ions,OC and EC,and the sources of atmospheric particles were analyzed.Combined with the backward trajectory,the migration of atmospheric particles was examined under heavy pollution.And some measures were proposed in Laiwu.?1?The concentrations of PM₁₀ from 2015 to 2017 were 134.25?g/m³,126.17?g/m³ and113.00?g/m³,respectively,and the concentrations of PM_2.5 were 85.50?g/m³,72.42?g/m³and 60.36?g/m³,respectively.It appeared a trend of decreasing year by year.There was a obvious seasonal changes,and the pollution was highset in winter.This is mainly related to the energy structure of Laiwu City,and the soot-type pollution is typical of air pollution.In 2016,the ratio of PM_2.5/PM₁₀ was 0.46-0.74,and the ratio of PM_2.5/PM₁₀ in winter was the highest,which indicated that fine particulate pollution is the main in the heating season.The ratio of PM_2.5/PM₁₀ in the spring was the lowest,indicating that sandstorm season is dominated by coarse particles.There was a positive correlation between NO₂ and PM_2.5,and there was a negative correlation between O₃ and PM_2.5 concentrations.?2?The secondary ions(SO₄^2-?NO₃^-and NH₄⁺)in all periods were the most important water-soluble inorganic ions,accounting to more than 70%of the total,indicating that the secondary pollution is mainly in Laiwu City.In 2016,three ions exist mainly in the form of NH₄NO₃ and?NH₄?₂SO₄.The formation of nitrates in the ammonium-depleted samples was related to the heterogeneous hydrolysis of high humidity and N₂O₅ on the surface of acidic aerosols in Laiwu City.Through the ratio of[NO₃^-]/[SO₄^2-],the summer was based on a fixed source,while the spring,autumn and winter are mainly flow sources.The concentration of OC and EC increased with the increase of the particle size,and the value of OC/EC decreased with the increase of particle size,indicating that the secondary pollution was more serious in the fine particles.?3?Using the CMB model to analyze the highest sharing rate of PM_2.5 source for coal-fired dust during the heating season,the highest sharing of PM_2.5 in the spring is urban dust,and the highest sharing rate in summer and autumn is sulfate and Nitrate.From the perspective of the secondary distribution of atmospheric emission sources,the highest sharing rate of PM_2.5 sources in the heating season,autumn,and summer is industrial production,followed by dust,and the highest proportion of in the spring is dust,followed by industrial production.?4?Using the backward trajectory model to analyze the backward trajectory of air mass during heavy pollution.There was a large roundabout phenomenon in the northwest at height of 500m on January 3^th-4^th,accounting for 66.7%of the total,while accounted for 16.7%in the southwest,with a small part coming from the interior of Shandong Province,accounting for 16.6%,the speed is extremely slow,leading to the concentrations of pollutants increasing.