Nonagricultural Emissions Dominate Urban Atmospheric Amines as Revealed by Mobile Measurements

Gaseous amines have recently been identified as the key precursors for frequent new particle formation in polluted urban atmospheres. An open question that arises is why amines are abundant in urban areas despite the absence of agricultural emissions. Here, using the Vocus Proton‐Transfer‐Reaction Time‐of‐Flight Mass‐Spectrometry Mobile Laboratory, we present highly time‐resolved and ultrasensitive measurements of amines to elucidate their atmospheric abundance and source distribution over the Yangtze River Delta city cluster. Our results show strong spatiotemporal heterogeneity in atmospheric C2‐ and C3‐amine levels across various landscapes. Unexpectedly, we found that urban areas were ubiquitous hotspots of amines while amine source strength from agricultural areas were rather low. Corroborated by source measurements and source tracers, all of the evidence suggest that nonagricultural emissions are the most important sources responsible for the observed patterns of urban atmospheric amines, implying significant consequences for the global amine emission inventory. Plain Language Summary Recently, the cluster formation of sulfuric acid‐dimethylamine‐H2O has been identified as an important mechanism to explain the frequent formation of new particles in urban polluted atmospheres. However, the interest in gaseous amines across the aerosol scientific community contrasts sharply with the extremely sparse information on their sources and atmospheric abundance. In this study, we present the first mobile measurements showing that the source strength of amines from agricultural areas is modest, thus questing the long‐held assumption that the agricultural sources of amines are similar to those of ammonia. In the case of C2 amines, industrial processes are considered to be an important emission pathway. The dominance of nonagricultural sources, such as fuel combustion, in C3 amines is likely to assign these volatile amine compounds a key function in enhancing new particle formation in polluted atmospheres. Key Points Mobile measurements are a powerful approach to map major sources of gaseous amines In highly urbanized areas, nonagricultural emission sources dominate atmospheric amines C2 and C3 amines are mainly originated from industrial and mobile sources, respectively