Ship-based MAX-DOAS measurements of tropospheric NO<sub>2</sub>, SO<sub>2</sub>, and HCHO distribution along the Yangtze River

Abstract

Abstract. In this paper, we present ship-based MultiAxis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of tropospheric trace gases' distribution along the Yangtze River during winter 2015. The measurements were performed along the Yangtze River between Shanghai and Wuhan, covering major industrial areas in eastern China. Tropospheric vertical column densities (VCDs) of nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), and formaldehyde (HCHO) were retrieved using the air mass factor calculated by the radiative transfer model. Enhanced tropospheric NO 2 and SO 2 VCDs were detected over downwind areas of industrial zones over the Yangtze River. In addition, spatial distributions of atmospheric pollutants are strongly affected by meteorological conditions; i.e., positive correlations were found between concentration of pollutants and wind speed over these areas, indicating strong influence of transportation of pollutants from high-emission upwind areas along the Yangtze River. Comparison of tropospheric NO 2 VCDs between ship-based MAX-DOAS and Ozone Monitoring Instrument (OMI) satellite observations shows good agreement with each other, with a Pearson correlation coefficient (R) of 0.82. In this study, the NO 2 / SO 2 ratio was used to estimate the relative contributions of industrial sources and vehicle emissions to ambient NO 2 levels. Analysis results of the NO 2 / SO 2 ratio show a higher contribution of industrial NO 2 emissions in Jiangsu Province, while NO 2 levels in Jiangxi and Hubei provinces are mainly related to vehicle emissions. These results indicate that different pollution control strategies should be applied in different provinces. In addition, multiple linear regression analysis of ambient carbon monoxide (CO) and odd oxygen (O x ) indicated that the primary emission and secondary formation of HCHO contribute 54.4 ± 3.7 % and 39.3 ± 4.3 % to the ambient HCHO, respectively. The largest contribution from primary emissions in winter suggested that photochemically induced secondary formation of HCHO is reduced due to lower solar irradiance in winter. Our findings provide an improved understanding of major pollution sources along the eastern part of the Yangtze River which are useful for designing specific air pollution control policies.

Primary and secondary sources of ambient formaldehyde in the Yangtze River Delta based on Ozone Mapping and Profiler Suite (OMPS) observations

“…The FTS total systematic error of the HCHO retrieval is less than 3.3 %, and the total random error is less than 9.6 % . Due to the high accuracy, the trace gas concentrations measured using FTS have been widely used to validate corresponding satellite products (Yamamori et al, 2006;Jones et al, 2009;Yurganov et al, 2010;Reuter et al, 2011).…”

Spatial distribution and seasonal variability in atmospheric ammonia measured from ground-based FTIR observations at Hefei, China

“…Hefei, located in eastern China, is a highly populated and polluted region, with intensive agricultural production, heavy traffic and transportation. Hefei has suffered severe haze and poor visibility in recent years (Hong, et al, 2018;Tan et al, 2019). Concentrations of PM2.5 often exceed the Ambient Air Quality Standard in autumn and winter.…”

Surveillance of SO<sub>2</sub> and NO<sub>2</sub> from ship emissions by MAX-DOAS measurements and implication to compliance of fuel sulfur content

“…As an expanded apparatus, the multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements are high sensitivity to aerosols and trace gases in the lower troposphere by observing scattered sunlight under different viewing angles closed to the horizontal and the zenith directions (Hönninger et al, 2004;Ma et al, 2013;Sinreich et al, 2005;Wang et al, 2014). Due to its portability, MAX-DOAS instrument can be carried on the ship to observe the vertical column densities (VCDs) of NO2 and SO2 along the cruise, during which high levels of pollutants were found close to the busy port and dense lanes (Hong et al, 2018;Schreier et al, 2015;Takashima et al, 2012;Tan et al, 2018). In addition, MAX-DOAS has been successfully employed for monitoring shipping emissions directly.…”