Occurrence Patterns and Generation Characteristics of Secondary Inorganic Ions in PM2.5 at Different Pollution Levels in Changsha City in Winter
Based on the online monitoring data of secondary inorganic ions(SNA)in PM2.5,gaseous pollutants and the meteorological factors,this study analyzed the variation characteristics,occurrence patterns and generation characteristics of secondary inorganic ions in PM2.5 at different pollution levels.The results showed that the mean concentrations of NO3-,SO42-and NH4+were(20.6±14.1)μg/m3,(7.0±3.9)μg/m3,(5.2±2.8)µg/m3,respectively.SNA accounted for 53.9％of PM2.5 mass concentration,and NO3-was the main contributor.The concentrations of SNA on pollution days were 1.3 times higher than those on clean days,and NO3-increased the most.Compared to the clean days,NO2,SO2 and relative humidity are higher on pollution days.SNA existed primarily as(NH4)2SO4 and NH4NO3 on clean days.However,SNA mainly existed in the form of(NH4)HSO4 and NH4NO3 on pollution days.The average pH of aerosol in Changsha was 3.1,with higher acidity observed on pollution days.The mean values of sulfur oxidation ratio(SOR)and nitrogen oxidation ratio(NOR)were higher on pollution days than on clean days.The correlation between SOR,NOR and AWC on pollution days was also significantly higher than on clean days.The generation of SO42-was dominated by liquid-phase reaction,and the generation of NO3-was dom-mated by heterogeneous hydrolysis on pollution days.Overall,AWC promoted SOR and NOR.
PM2.5 pollutionsecondary inorganic ions(SNA)secondary generationAerosol water content(AWC)
NETL
NSTL
万方数据
