Characteristics of atmospheric non-methane hydrocarbon compounds (NMHCs) and their sources in urban typical secondary transformation in Beijing, China

Abstract

Non-methane hydrocarbon compounds (NMHCs) paly the leading role in the formation of ozone (O3) and secondary organic aerosols (SOA), which can affect severely global climate change, air quality, and human health. NMHCs pollution became a meaningful and crucial research topic in Beijing. From the Eleventh Five-Year Plan to the present, volatile organic compounds (VOCs) have received widespread and great attention in environmental governance, especially the NMHCs. Due to successive stages to control air pollution, the concentration of NMHCs has dropped gradually nearly three years in Beijing. In this study, 54 NMHCs was measured from March 1 to March 30 in 2021. The mean concentration of NMHCs was 33.54 ± 16.69 ppbv during the whole observation period. The mean concentration of NMHCs was 40.69 ± 17.09 ppbv during the haze days, which was greater than non-haze days (26.68 ± 12.75 ppbv). Alkenes, alkanes, aromatics, and acetylene accounted for 34.22%, 33.02%, 32.60%, and 016% in total ozone formation potential (OFP), respectively. Aromatics accounted for 96.61% in total secondary organic aerosol potential (SOAP). All the sources of NMHCs (except for fuel evaporation) made non-negligible contribution to O3 formation. Solvent usage and gasoline exhaust contributed 52.19%, which were the largest contributor to SOAP. Therefore, Beijing should focus on the NMHCs pollution caused by the local emission (especially solvent usage and gasoline exhaust) to control and solve secondary pollution further in this study.