Abstract. In this study, ship-based multi-axis differential optical
absorption spectroscopy (MAX-DOAS) measurements were performed in the East
China Sea (ECS) area in June 2017. The tropospheric slant column densities
(SCDs) of nitrogen dioxide (NO2), sulfur dioxide (SO2), and
formaldehyde (HCHO) were retrieved from the measured spectra using the
differential optical absorption spectroscopy (DOAS) technique. Using the
simple geometric approach, the SCDs of different trace gases observed at a
15∘ elevation angle were adopted to convert into tropospheric
vertical column densities (VCDs). During this campaign, the averaged VCDs of
NO2, SO2, and HCHO in the marine environment over the ECS area are 6.50×1015, 4.28×1015, and 7.39×1015 molec cm−2, respectively. In
addition, the ship-based MAX-DOAS trace gas VCDs were compared with
satellite observations of the Ozone Monitoring Instrument (OMI) and Ozone Mapping
and Profiler Suite (OMPS). The daily OMI NO2 VCDs agreed well with
ship-based MAX-DOAS measurements showing the correlation coefficient R of
0.83. In addition, the good agreements of SO2 and HCHO VCDs between the OMPS
satellite and ship-based MAX-DOAS observations were also found, with
correlation coefficients R of 0.76 and 0.69. The vertical profiles of these
trace gases are achieved from the measured differential slant column
densities (DSCDs) at different elevation angles using the optimal estimation
method. The retrieved profiles displayed the typical vertical distribution
characteristics, which exhibit low concentrations of <3,
<3, and <2 ppbv for NO2, SO2, and HCHO in a clean
area of the marine boundary layer far from coast of the Yangtze River Delta
(YRD) continental region. Interestingly, elevated SO2 concentrations can
be observed intermittently along the ship routes, which is mainly attributed
to the vicinal ship emissions in the view of the MAX-DOAS measurements.
Combined with the on-board ozone lidar measurements, the ozone (O3)
formation was discussed with the vertical profile of the HCHO∕NO2 ratio,
which is sensitive to increases in NO2 concentration. This study
provided further understanding of the main air pollutants in the marine
boundary layer of the ECS area and also benefited the formulation of policies
regulating the shipping emissions in such costal areas like the YRD region.
Seasonal variations of stable carbon isotopic composition of bulk aerosol carbon from Gosan site, Jeju Island in the East China Sea
