Nitrogen Oxides Spatial Distribution and Emissions with Mobile Multi-Axis Differential Optical Absorption Spectroscopy in Wuhan City

For NOx, pollutions in Wuhan during the outbreak of COVID-19, we applied a mobile MAX-DOAS and a portable ultraviolet DOAS to cooperatively measure NOx, concentration in the third ring road of Wuhan from Feb. 29th to Mar. 14th, 2020. The mobile MAX-DOAS acquired the vertical column concentration (VCD) distribution of NO2 along its course and the portable ultraviolet DOAS measured the NO and NO2 concentrations to calculate [NOx]/[NO2]. Then, the NOx emission flux and its error of the third ring road of Wuhan were calculated in conjunction with the data of the wind field. The results show that the NO, emission flux during the measurements in the third ring of Wuhan ranges from 7.78 mol/s to 15.71 mol/s, about 10.78 mol/s on average. Compared with the average [NOx]/[NO2], the real-time [NOx]/[NO2] along the route of the mobile MAX-DOAS derived from the portable ultraviolet DOAS could effectively reduce the error of NOx emission flux caused by the [NOx,]/[NO2] error. However, this method is not recommended in scenarios with substantial near-surface NOx emission sources.

Automated summary

In investigating NOx pollution in Wuhan during the COVID-19 outbreak, researchers used a mobile MAX-DOAS and a portable ultraviolet DOAS to measure the NOx concentration in the third ring road. The study found that the average NOx emission flux was approximately 10.78 mol/s, and using the combination of mobile MAX-DOAS and portable ultraviolet DOAS effectively reduced measurement errors, but may not be suitable for areas with significant near-surface NOx emission sources.