Study on Measurement of Troposphereic NO2 in Beijing by MAX-DOAS

Due to the importance of nitrogen dioxide (NO2) in the atmospheres physical and chemical processes and its impact on the environment, climate and human health, reasonable and effective monitoring and control of NO2 concentration in the atmosphere has become a very important topic.The Differential optical absorption spectroscopy (MAX-DOAS) instrument is a passive DOAS instrument that uses the suns scattered light. Compared with the point type instrument which measures in a small range and the active DOAS instrument that uses the light source and reflection device, it has high time resolution, high sensitivity, wide measurement range and not restricted by the platform. In 2018, the annual continuous observation of tropospheric NO2 based on ground-based MAX-DOAS was carried out at the China Academy of Meteorological Sciences (116.32 degrees E, 39.95 degrees N) in Beijing. The original absorption spectra were collected and retrieved using the spectral processing software QDOAS to obtain the NO2 slant column concentration (SCD). Combined with the simpler geometric approximation method of atmospheric quality factor (AMF), the NO2 SCD was converted into vertical column concentration (VCD), and based on this, the Beijing area was studied and analyzed. The characteristics of monthly and seasonal mean change of NO2 VCD, seasonal daily mean change and daily mean change in a week. The results show that the tropospheric NO2 VCD changes obviously with seasons in Beijing, showing the highest in winter and the lowest in summer. The mean value in winter is 2.94x10(16) molec.cm(-2), which is 1.6 times that in summer. The average daily change in different seasons generally shows the obvious difference in the afternoon, and the maximum difference is 2.17x10(16) molec.cm(-2). There is a certain regularity in the daily concentration change in a week. The average concentration on Sunday is about 17% lower than that on other days, and there is a certain weekend effect. By comparing the observation results of MAX-DOAS on the ground with the state control stations data on the ground, the change trend of the two has good consistency, and the correlation coefficient r can reach 0.81. The research shows that ground-based MAX-DOAS can provide an effective means for real-time and rapid monitoring of regional pollution gases and analysis of variation rules and can verify the data obtained from other sources.