To elucidate the variation characteristics and influencing factors of water-soluble inorganic ions(WSIIs)in PM2.5 during the heavy pollution period of the Spring Festival under the influence of air pollution control and COVID-19 epidemic,the concentrations of WSIIs in PM2.5 during two heavy pollution periods occurred in the three consecutive Spring Festival holidays in Tianjin from 2018 to 2020 were comparably investigated.The results showed that the average PM2.5 concentration in 2018(98.32 μg·m-3)and in 2020(137.7 μg·m-3)was significantly higher than that in 2019(49.97 μg·m-3).The average PM2.5 concentration in the period Ⅱ of heavy pollution episode in 2020(206.5 μg·m-3)was 2.1 times higher than that in the period Ⅰ in 2018(98.32 μg·m-3).The concentration of NO2 in the two pollution periods changed little,while the average concentration of SO2 in the period Ⅱ(14.89 μg·m-3)was 49.6％of that in the period Ⅰ(30.04 μg·m-3).The SNA accounted for more than 77％of the WSIIs,and were mainly in the forms of NH4NO3 and(NH4)2SO4 among which NH4NO3 was the most important inorganic salt and it's concentration in the period Ⅱwas much higher than that in the period Ⅰ.In addition,PM2.5/CO,SOR and NOR in the period Ⅱsignificantly increased,indicating that the more effective formation of SO42-and NO3-was one of the main reasons for the high concentration of PM2.5 in the period Ⅱ.Adverse meteorological conditions such as low boundary layer height,high relative humidity and low wind speed resulted in stable and strong inversion weather,which led to the reduction of atmospheric environmental capacity and greatly improved the generation efficiency of secondary inorganic aerosols during the period Ⅱ,thus offsetting the impact of epidemic effect and emission reduction measures.For the period Ⅰ,in addition to secondary transformation,PM2.5 concentrations may be more affected by regional transmission.
关键词
春节/水溶性无机离子/SNA/形成机制/天津
Key words
Spring Festival/water-soluble inorganic ions/SNA/formation mechanism/Tianjin
万方数据