霾不同发展阶段下污染气体和水溶性离子变化特征分析

Change in Characteristics of Pollution Gas and Water-soluble Ions at Different Development Stages of Haze

为探讨霾不同阶段下大气污染物的变化特征,使用MARGA观测了2018年11月18日~12月7日长三角地区一次区域霾过程中前体污染气体(NH3、HNO3、SO2)和8种水溶性离子浓度.结合环保数据(PM2. 5、NO2、CO、O3)和气象数据,分析此次区域霾过程的成因、大气污染物的日变化特征以及在霾不同阶段下大气污染物的分布特征.结果表明,此次霾过程中长三角地区主要受到高压脊控制,天气形势稳定,有利于大气污染物累积.霾天时PM2. 5、NO2、NO3-、SO24-、NH4+、Cl-和Na+的浓度分别为(118. 91±39. 23)、(61. 62±26. 34)、(45. 64±16. 01)、(18. 80±8. 02)、(20. 82±7. 16)、(3. 02±2. 25)和(0. 23±0. 22)μg·m-3,分别是干净天的2. 73、1. 63、2. 64、1. 94、2. 50、2. 05和2. 56倍;霾天CO的浓度为(1. 34±0. 39)mg·m-3,是干净天的1. 86倍.不同大气污染物的日变化特征不同.霾不同阶段下大气污染物的分布特征不同. SO2的浓度在霾发生阶段最高;PM2. 5、NO2、NH3、CO和SNA的浓度在霾发展阶段最高;O3、Cl-、Na+和K+的浓度在霾消散阶段最高.SNA在霾不同阶段下对PM2. 5的相对贡献可达94%~96%,且在发展阶段的增速最大,增速排序为NO3-> NH4+> SO24-. SNA在干净天、发生阶段和发展阶段以NH4NO3为主,在消散阶段(NH4)2SO4为主.此次霾过程主要由NO3-增长导致,NO3-在霾发生、发展和消散阶段对PM2. 5的相对贡献分别为51. 06%、51. 85%和48. 22%,主要通过气相均相反应生成.

To explore the variation in characteristics of atmospheric pollutants at different stages of haze,the monitor for aerosols and gases in ambient air(MARGA)was used to observe the concentrations of precursor pollutants(NH3,HNO3,and SO2)and eight water-soluble ions in a regional haze in the Yangtze River Delta region from November 18 to December 07,2018.Combined with environmental data(PM2.5,NO2,CO,and O3)and meteorological data,the causes of regional haze formation,diurnal variation characteristics of air pollutants,and distribution characteristics of air pollutants in different stages of haze were analyzed.The results showed that the Yangtze River Delta region was mainly controlled by a ridge of high pressure during the haze process and the weather situation was stable,which was conducive to the accumulation of air pollutants.On hazy days,the concentrations of PM2.5,NO2,NO-3,SO2-4,NH+4,Cl-,and Na+were(118.91±39.23),(61.62±26.34),(45.64±16.01),(18.80±8.02),(20.82±7.16),(3.02±2.25),and(0.23±0.22)μg·m-3,respectively,and these were 2.73,1.63,2.64,1.94,2.50,2.05,and 2.56 times the levels found on clean days,respectively.The concentration of CO was(1.34±0.39)mg·m-3 on hazy days,which was 1.86 times that found on clean days.Diurnal variation characteristics of different air pollutants were different,as were the distribution characteristics of air pollutants at different haze stages.The concentrations of SO2 was the highest in the haze occurrence stage.The concentrations of PM2.5,NO2,NH3,CO,and SNA were highest in the haze development stage,and the concentrations of O3,Cl-,Na+,and K+were highest in the haze dissipation stage.The relative contributions of SNA to PM2.5 in different stages of haze could reach 94%-96%,and their growth rate was largest in the development stage.The order of growth rate was NO-3>NH+4>SO2-4.SNA mainly existed in the form of NH4NO3 on clean days and in the occurrence and development stages,and(NH4)2 SO4 in the dissipation stage.This haze process was mainly caused by the growth of NO-3,which was mainly generated by gas-phase homogeneous phase reaction,and NO-3 contributes 51.06%,51.85%,and 48.22%,respectively,to PM2.5 in the occurrence,development,and dissipation stages of haze.