An Increase in Primary Formaldehyde Emissions Induced by the Coal-to-Gas Policy in Beijing

Abstract

In recent years, China has implemented the "coal-to-gas" strategy. The source composition spectra of pollutants emitted from coal and natural gas combustion are substantially different. Therefore, changes in the energy structure may lead to a significant impact on the atmospheric formaldehyde (HCHO) concentration and sources. To investigate the changes in HCHO sources, this study used proton transfer reaction-time-of-flight/mass spectrometry to observe and analyze HCHO in Beijing in May (spring), August (summer), and October (autumn) of 2019 and January (winter) of 2020. The average concentrations during the observation period were 5.1 ± 2.5 ppb (spring), 7.2 ± 1.9 ppb (summer), 3.6 ± 1.9 ppb (autumn), and 1.8 ± 0.5 ppb (winter), showing a characteristic of a single peak (midday) variation. Using nonmethane hydrocarbons as tracers, the source contributions of HCHO were quantified by the positive matrix factorization method. The results showed that the average contribution of secondary + biogenic was 2.2 ppb throughout the year, while the average contribution of anthropogenic primary was 1.5 ppb, accounting for 60.0% and 40.0% of the total concentration, respectively. Importantly, compared with 2011, the contribution of anthropogenic primary increased considerably, by 18.2% in winter, which has a significant relationship with "coal-to-gas". This study emphasizes the importance of primary HCHO emissions from natural gas. With the deep promotion of "coal-to-gas", it is necessary to strengthen the control of pollutants directly emitted from natural gas combustion in the future.

Keywords: primary HCHO, coal to gas, source appointment, PMF