Study On The Chemical Composition Of PM_2.5 And The Health Effects Of Persistent Free Radicals In A Typical Urban Area Of ​​the Three Gorges Reservoir

Atmospheric particulate pollution caused by industrialization and urbanization is frequent,causing concerns worldwide.PM_2.5can impact visibility,air quality,climate,and human health.PM_2.5has become the primary pollutant of ambient air quality in most cities in China.Southwestern China has also suffered from the particulate pollution,especially in the Three George Reservoir（TGR）region.Wanzhou is one of the typical industrial cities in the TGR region.In order to study the pollution characteristics of PM_2.5and its impact on human health in Wanzhou District,we set up sampling points in Wanzhou City from April 2017 to February 2018 to collect PM_2.5particulates.Ion chromatograph,DRI-2015 thermo-optical carbon analyzer,and electromagnetic resonance spectrometer wave spectrometer analyze water-soluble ions,organic carbon OC,elemental carbon EC and environmentally persistent free radical EPFRs in PM_2.5.The main results are as follows:（1）The average annual concentration of PM_2.5is 28.3 μg·m^-3,and the seasonal variation is shown as winter> autumn> spring> summer.Mass reconstruction analysis showed that OM and SO₄^2-are the two components with the highest content of PM_2.5in Wanzhou,38.8% and 19.9% of PM_2.5respectively.（2）During the sampling period,the water-soluble ions in PM_2.5in Wanzhou were relatively basic.SO₄^2-,NO₃^-,and NH₄⁺ were the three ions with the highest proportion of water-soluble ions,accounting for 37.4%,24.6% and 18.1%.（3）PM_2.5,carbonaceous components,and other components have the same change trend,and the concentrations in winter are significantly higher than in summer.The percentage of SOC in each season is 54.3% in winter> 52.1% in autumn> 40.7% in spring> 28.0% in summer,indicating that SOC is an important part of OC.（4）During the sampling period,the average concentration of EPFRs in PM_2.5was 7.0×10¹³spins·m^-3,which was mainly free radicals with adjacent oxygen atoms centered on carbon.Particulates from coal combustion,transportation,secondary formation and agriculture are important sources of EPFRs in PM_2.5.（5）The health impact assessment shows that in 2017,EPFRs per person inhaled per day in Wanzhou was equivalent to 2.3 cigarettes,reaching 840 cigarettes throughout the year,and the risk of exposure was relatively large.