Assessment of HCHO in Beijing during 2009 to 2020 using satellite observation and numerical model: Spatial characteristic and impact factor

Formaldehyde (HCHO) is an air pollutant that has a detrimental effect on human health and atmospheric environment. Until now, satellite observation has been increasingly a valuable source for monitoring the unconventional atmospheric pollutants due to the limited availability of ground-based HCHO data. Here, we used Ozone Monitoring Instrument (OMI) and the weather research and forecasting with chemistry (WRF-Chem) model to synergistically analyze the spatiotemporal variations of tropospheric HCHO in Beijing during 2009-2020, and the response of O3 to HCHO and NO2 in hotspots. We also discuss the multiple factors influencing the variation of HCHO and identify potential source area. The results indicated that HCHO column concentration is higher in eastern Beijing, and peaking in 2018 (16.68 x 1015 mol/cm2). O3 shows a good response to HCHO, with higher HCHO and NO2 photolysis leading to O3 increase in summer. In winter, decreasing HCHO and increasing NO2 inhibits the formation of O3. Transportation emissions contributed the most to HCHO, followed by the industrial sector, while residential sources have long-term effects. Isoprene produced by plants is one of the main sources of HCHO, whereas meteorological conditions can affect production efficiency. Biomass burning contributes less. Moreover, HCHO in Beijing is affected by the combined effects of local emission and external transport, and Hebei is the potential source area. This study reveals HCHO has a great accumulation potential in cities and highlights the dominant role of anthropogenic emissions, but also need to consider the influence of natural factors and regional transport.

Automated summary

This study used satellite observations and modeling to analyze the spatiotemporal variations of tropospheric formaldehyde (HCHO) in Beijing from 2009 to 2020 and examine the factors influencing its variation. The results showed that eastern Beijing had higher HCHO concentrations, peaking in 2018. HCHO exhibited a good response to ozone (O3), with higher HCHO and nitrogen dioxide (NO2) photolysis leading to O3 increase in summer, while decreasing HCHO and increasing NO2 inhibited O3 formation in winter. Transportation emissions were the largest contributor to HCHO, followed by the industrial sector, and residential sources had long-term effects. Isoprene produced by plants was one of the main sources of HCHO, and meteorological conditions influenced its production efficiency. This study revealed the potential accumulation of HCHO in cities and highlighted the dominant role of anthropogenic emissions, while also emphasizing the influence of natural factors and regional transport.