More Complete Reactive Organic Gases Measurements Reveal Greater Role of Combustion Emissions in Shanghai Megacity

Abstract Significant differences exist in molecular profiling of reactive organic gases (ROG) across different analytical techniques, hindering our understanding on their atmospheric characteristics and sources. Photochemical assessment monitoring stations (PAMS) routinely measure a key group of ROG, that is, hydrocarbons, which have been used for source apportionment in past decades. This study took Shanghai megacity as an example to investigate the differences in chemical characteristics and source apportionment between PAMS species and a more comprehensive set of ROG, including high‐carbon alkanes, terpenoids, N‐containing and oxygenated species. We found PAMS species accounted for only 44.1% and 24.7% of ROG, respectively, in carbon concentration and OH reactivity. Comprehensive ROG characterization especially advances in source attribution: (a) source apportionment based on ROG species (ROG method) resolved nine sources compared to PAMS method, which resolved six sources with two of them remained as mixed sources, and among the newly identified sources by ROG method, three were attributed to combustion activities, specifically, diesel, coal, and biomass combustion; (b) improved temporal correlations between resolved sources and the corresponding tracers, such as gasoline exhaust, fuel evaporation, and solvent usage further confirming the source origin; (c) increased fractional contributions from industrial and combustion sources. To summarize, we found fugitive sources (solvent usage, fuel evaporation, and industrial process) dominated with PAMS method, but combustion sources outweighed fugitive sources with ROG method. These distinct results indicate PAMS method may underestimate combustion‐related ROG emissions. Although current clean air policies focus on the abatement of fugitive sources, combustion emission reductions require greater future attention.