Characteristic Changes Of PM_2.5 Pollution In Typical City In Shandong Province And The Influence Of Policies On It

PM2.5 has an important impact on human and health climate change.Jinan,was selected as the research site,it is the capital city of Shandong Province.The study was carried at urban and suburban sites of Jinan at the important turning points(2006,2016 and 2021)in the FiveYear plans.The pollution characteristics of water-soluble inorganic ions,carbon particles and elements in PM2.5 in different years,different seasons(winter and summer)and different functional districts(urban and suburban sites)were analyzed.The spatial-temporal characteristics of regional transport and source were studied by backward trajectory,potential source analysis and source apportionment model.At the same time,the impact of the relevant policies introduced and implemented by the national and local governments at different stages on PM2.5 pollution was analyzed.The results revealed that from 2006 to 2021 the average concentration of PM2.5 in Jinan decreased significantly.The transformation of PM2.5 pollution was from sulfuric acid type to nitric acid type.The concentrations of K+ and Cl-decreased significantly,while the carbon component showed a downward trend,and the proportion of EC in carbon species decreased from 3.04%to 1.96%,which was attributed to the reduced influence from the primary emission.The concentration of total trace elements increased significantly,and compared with enrichment factors,it was found that elements such as Pb and Zn showed a decreasing trend,while elements such as Cu and Mg showed an increasing trend.These were related to the fact that since the 11th Five-Year Plan,Jinan had made great efforts to develop the automobile industry and improve environmental protection in the coal-burning industry.For example,the Adjustment and Revitalization Plan of Jinan A utomobile Industry released in 2009 mentioned to maintain the steady development of the automobile industry.In the "13th Five-Year" energy conservation and emission reduction comprehensive work Plan of Jinan City,desulfurization facilities and ultra-low emission transformation projects were required for coal-fired power plants,petrochemical refining and steel industries.In addition,in air pollution prevention,strictly prohibiting crop straw burning effectively reduced the emissions from the biomass burning;in order to prevent and control environmental risks of heavy metals,comprehensive treatment of major heavy metal pollutants had been carried out.According to the season,the average concentration of PM2.5 and its main components in winter were much higher than that in summer,which was related to human activities such as coal burning in winter.The average concentration of PM2.5 and its main components at the urban site were similar to those at the suburban site,indicating the differences between urban and suburban PM2.5 pollution were gradually decreasing.Compared to the urban site,biomass burning and transportation sources contributed more at the suburban site.In 2021,atmospheric transmission is more complicated,and the influence of atmospheric regional transmission in Jinan was increased in the surrounding areas.The simulation results of PSCF revealed that the potential source areas of PM2.5 pollution were significantly reduced,illustrating the joint prevention and control work was effective and Shandong Province was the main potential source area of PM2.5 in Jinan in both winter and summer.The PMF source apportionment results showed that with the increase of years,the contribution of traffic source increased significantly,while the contributions of dust source,industrial source and combustion source showed a decreasing trend,which may be due to the implementation of dust pollution prevention measures,such as strengthening dust management at the construction site,improving the cleaning level of pavement,etc.;limited the development scale of the metallurgical industry in the city,strictly controlled the construction of coking production lines and other policies.At the same time,the second formation had been playing an important role.The contributions of all sources were similar in winter and summer except to the higher contribution from combustion source in winter than that in summer.The contribution of all sources were similar with secondary source>traffic source>mixed primary source>dust source>industrial source and the contribution is near for the same source at the urban and suburban sites.