Observation on the aerosol and ozone precursors in suburban areas of Shenzhen and analysis of potential source based on MAX-DOAS.

Long-term stereoscopic observations of aerosol, NO, and HCHO were carried out at the Yangmeikeng (YMK) site in Shenzhen. Aerosol optical depths and NO vertical column concentration (NO VCD) derived from MAX-DOAS were found to be consistent with other datasets. The total NO VCD values of the site remained low, varying from 2 × 10 to 8 × 10 mol/cm, while the HCHO VCD was higher than NO VCD, varying from 7 × 10 to 11 × 10 mol/cm. HCHO VCD was higher from September to early November than that was from mid-late November to December and during February 2021, in contrast, NO VCD did not change much during the same period. In January, NO VCD and HCHO VCD were both fluctuating drastically. High temperature and HCHO level in the YMK site is not only driving the ozone production up but also may be driving up the ozone concentration as well, and the O production regime in the YMK site tends to be NO-limited. At various altitudes, backward trajectory clustering analysis and Potential Source Contribution Function (PSCF) were utilized to identify possible NO and HCHO source locations. The results suggested that the Huizhou-Shanwei border and the Daya Bay Sea area were the key potential source locations in the lower (200 m) and middle (500 m) atmosphere (WPSCF > 0.6). The WPSCF value was high at the 1000 m altitude which was closer to the YMK site than the near ground, indicating that the pollution transport capability in the upper atmosphere was limited.