Observations by Ground-Based MAX-DOAS of the Vertical Characters of Winter Pollution and the Influencing Factors of HONO Generation in Shanghai, China

Abstract

Analyzing vertical distribution characters of air pollutants is conducive to study the mechanisms under polluted atmospheric conditions. Nitrous acid (HONO) is a kind of crucial species in photochemical cycles. Exploring the influence and sources of HONO in air pollution at different altitudes offers some insights into the research of tropospheric oxidation chemistry processes. Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements were conducted in Shanghai, China, from December 2017 to March 2018 to investigate vertical distributions and diurnal variations of trace gases (NO2, HONO, HCHO, SO2, and water vapor) and aerosol extinction coefficient in the boundary layer. Aerosol and NO2 showed decreasing profile exponentially, SO2 and HCHO concentrations were observed relatively high values in the middle layer. SO2 was caused by industrial emissions, while HCHO was from secondary sources. As for HONO, below 0.82 km, the heterogeneous reactions of NO2 impacted on forming HONO, while in the upper layers, vertical diffusion might be the dominant source. The contribution of OH production from HONO photolysis at different altitudes was mainly controlled by the concentration of HONO. MAX-DOAS measurements characterize the vertical structure of air pollutants in Shanghai and provide further understanding for HONO formation, which can help deploy advanced measurement platforms of regional air pollution over eastern China.

Differences in the Vertical Distribution of Aerosols, Nitrogen Dioxide, and Formaldehyde between Islands and Inland Areas: A Case Study in the Yangtze River Delta of China

“…DOAS has been widely used in studies of the vertical distribution characteristics of atmospheric components in different environments (suburban, regional, island, and offshore) in different regions, e.g., the Beijing-Tianjin-Hebei [9,[17][18][19], the Pearl River Delta region [13,20,21] and the YRD region [22][23][24][25][26][27]. This technology provides a promising method for the accurate monitoring and management of air pollution.…”

“…The most important advantage of the MAX-DOAS is that it can simultaneously monitor various atmospheric components, including aerosols, NO 2 , and HCHO, thereby overcoming the errors of atmospheric component monitoring using different instruments. MAX-DOAS has been widely used in studies of the vertical distribution characteristics of atmospheric components in different environments (suburban, regional, island, and offshore) in different regions, e.g., the Beijing-Tianjin-Hebei [9,[17][18][19], the Pearl River Delta region [13,20,21] and the YRD region [22][23][24][25][26][27]. This technology provides a promising method for the accurate monitoring and management of air pollution.…”

Analysis of the Vertical Distribution and Driving Factors of Aerosol and Ozone Precursors in Huaniao Island, China, Based on Ground-Based MAX-DOAS

“…Air pollution is a complex mixture of gases and particulate matter with local and nonlocal emission sources, causing spatiotemporal variations in concentration and composition that carry associated health risks [1,2]. To be specific, aerosols are multiphase systems made up of solid, liquid, and gas particles suspended in the atmosphere that pose a serious threat to human health and limit the visibility of the atmospheric environment [3][4][5]. Nitrogen oxides (NO 2 ), one of the six conventional pollutants listed in China's air quality evaluation standards, can promote the generation of ozone.…”