军运会前后武汉市大气氨-铵气/粒转化监测研究

Atmospheric Gas-to-Particle Conversion Between NH and NH and Its Effect on PM Before, During and After Military World Games in Wuhan City

利用MARGA在线监测仪,作者对武汉城区2019年军运会前后大气中气态污染物与颗粒物水溶性离子(以NH3和SNA为主)的浓度进行连续采样,结合PM2.5及气象要素,分析了大气中NH3-NH4+气/粒转化及其对PM2.5的影响。结果表明,军运会管控前、中和后大气NH3浓度分别为(13.3±5.8)、(7.4±2.7)和(12.3±4.9)μg/m3,并且NH3、NH4+和PM2.5的日变化特征存在一定昼夜差异。利用潜在源贡献分析可知NH3和NH4+受外来传输的影响较小,结合其日变化特征说明NH3主要是武汉城区移动源排放。NH3-NH4+气/粒转化研究表明,军运会期间[NH3]∶[NH4+]比值均大于1,不利于NH3向NH4+转化,并且[NH3]:[NH4+]比值与PM2.5浓度存在一定负相关(R2=0.62)。在NH3充足的高湿环境中,NH3-NH4+气/粒转化率明显增加,其中NH4+主要以(NH4)2SO4和NH4NO3的形式存在,且NH4+更易与SO42-结合。

The mass concentrations of gaseous pollutants and particulate water-soluble ions(mainly NH3 and SNA) in the urban area of Wuhan were continuously measured before, during and after the 2019 Military World Games by the MARGA online monitor, which combined with PM2.5 and meteorological data to analyze gas-to-particle conversion between NH3 and NH4+. The results show that the concentration of NH3 before, during and after the Military World Games is(13.3±5.8)μg/m3,(7.4±2.7)μg/m3 and(12.3±4.9)μg/m3, respectively. There is some day-night differences in the daily changes of NH3,NH4+and PM2.5, and the PSCF shows that NH3 and NH4+is less affected by external transmission, indicating that NH3 mainly emissions from local mobile source in Wuhan. The study about gas-to-particle conversion between NH3 and NH4+shows that the [NH3]∶[NH4+] ratio is much greater than 1 before, during and after the Military World Games, it will go against the NH3 conversion, and the [NH3]∶[NH4+] ratio has a certain negative correlation with PM2.5 concentration(R2=0.62). In a high-humidity environment with sufficient NH3, the gas-to-particle percent conversion is increased, which NH4+obviously exists as the formation of(NH4)2SO4 and NH4NO3. And NH4+is more likely to combine with SO42-.