Secondary formation dominated low molecular weight amines origins in aerosols over the marginal seas of China

Abstract. Atmospheric low molecular weight amines play important roles in new particle formation, aerosol properties, and climate. However, the compositions, sources, and secondary formation mechanisms of amines in offshore aerosols remain unclear. Here, an integrated observation of methylamine (MA), ethylamine (EA), dimethylamine (DMA), iso-propanamine (IPA), propanamine (PA), "trimethylamine + diethylamine" (TMDEA), and > 100 other chemical components in total suspended particles was conducted during a spring 2018 research cruise across the Yellow Sea and Bohai Sea, China. Concentrations of total amines exhibited a north-to-south decrease from the Bohai Sea to the South Yellow Sea, corresponding to the declined influence of terrestrial air masses. Source analyses were performed by evaluating the linear relationships between individual amines and specific organic molecular tracers representing primary biogenic sources, higher plant waxes, marine/microbial sources, biogenic secondary organic aerosols (BSOA), biomass burning, and fossil fuel combustion. MA, EA, and DMA were largely influenced by terrestrial biogenic and anthropogenic sources, with the majority (74.0%, 52.6%, and 65.7%, respectively) formed through nitrate-associated secondary formation pathways, interacting with BSOA formation. PA was mainly derived from combustion-related sources, along with terrestrial and marine biogenic contributions. In contrast, the predominate amine, TMDEA, was mostly generated through sulfate-associated secondary formation pathways (61.8%) and contributed by marine emissions, leading to the north-to-south increase in its relative contribution to aerosol amines. The findings highlight distinct potential sources and formation mechanisms for different amines in offshore aerosols, and underscore the importance of multiphase chemistry of amines under varying ambient conditions.