Study On The Composition And Toxic Effects Of Inhalable Particulate Matter Emitted From Typical Motor Vehicle Exhaust

In recent years,the formation mechanism and health hazards of atmospheric haze have attracted worldwide attention.The toxic components and sources of inhalable particles have become a research hotspot,and the particulate matter emitted by traffic is an important object.In order to explore the contribution of traffic emissions to atmospheric particulate pollution hazards and compare the differences of different types of vehicle exhaust emissions on human health,this study selected the actual ambient air PM_2.5in different periods during a heavy pollution weather in Nanjing and the inhalable particulates(PM_2.5,PM₁₀)with different particle sizes from 10 typical vehicle exhaust emissions as the research objects.Based on the analysis and determination of the concentrations of carbon,metal elements and water-soluble ions in the particles,the cytotoxicity of various particles on A549 human lung epithelial cells in vitro was studied.The harm of various actual ambient air particulates and vehicle exhaust particulates on human health was revealed from three aspects of cell activity,oxidative damage and inflammatory damage.The main results are as follows:(1)The typical heavy pollution event in winter mainly comes from vehicle exhaust pollution,which is affected by the pollution air mass in the southwest.In addition,the meteorological conditions such as relative humidity and PM_2.5 concentration are significantly positively correlated,which makes PM_2.5 hygroscopic growth and causes PM_2.5 concentration to increase.Low wind speed makes atmospheric pollutants not easy to diffuse,resulting in continuous accumulation of pollutants.It was found that the higher the concentration of PM_2.5was,the stronger the toxic effect on cells was.The degree of oxidative damage and inflammatory damage(TNF-?)induced by PM_2.5 during the clean period was more serious than that during the pollution period.The change of metal composition indicates that this heavy pollution event is mainly affected by human factors,while the change of water-soluble ions indicates that traffic sources make major contributions to this heavy pollution event.(2)The particulate composition of two particle sizes of different types of motor vehicles is significantly different.For the carbon component,the content of gasoline vehicle is smaller than that of diesel vehicle,and the OC/EC of gasoline vehicle is much larger than that of diesel vehicle.For water-soluble ions,for all vehicle types,Na+,NO3-and SO42-account for the vast majority of the water-soluble components measured,which are related to the formation of NOx caused by high-temperature combustion and the production of a large amount of sulfate in the exhaust emission process.For metal elements,the metal content of gasoline vehicles is greater than that of diesel vehicles.One of the important reasons for the difference in the composition of particulate matter emitted by motor vehicles is the weight of the vehicle.In addition,with the tightening of vehicle emission standards,particulate matter emissions are also gradually reduced.(3)The two kinds of particles emitted by different types of motor vehicles can cause different aspects and degrees of cell damage.PM_2.5 emitted by the same type of motor vehicles has higher cytotoxicity than PM₁₀,resulting in a higher degree of decrease in cell activity,and the degree of oxidative damage caused by PM_2.5 is more serious than that caused by PM₁₀,while the degree of cellular inflammation caused by PM₁₀ is higher than that caused by PM_2.5.PM_2.5emitted from gasoline vehicles has strong cytotoxicity.With the improvement of motor vehicle emission standards,the toxic and harmful substances in exhaust gas are also reduced,and the harm to human health is weakened.To sum up,motor vehicle exhaust is still the main source of urban air pollution.For the treatment of motor vehicle exhaust,the diesel exhaust gas control device is recommended for diesel vehicles,which can effectively reduce the EC content in diesel vehicle exhaust PM_2.5.For small gasoline vehicles,the treatment is mainly aimed at reducing the formation of secondary organic carbon,minimizing the use of metal components,actively responding to the call of the state and improving emission standards.