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Abstract Snowfall plays a critical role in scavenging atmospheric dissolved organic matter (DOM) and modulating air quality in cold regions; however, the underlying molecular mechanisms remain poorly understood. Here, we investigated the DOM dynamics before, during, and after snowfall using Fourier transform ion cyclotron resonance‐mass spectrometry. Compared with the pre‐snowfall total suspended particles (TSP) sample, the post‐snowfall sample contained about 50% fewer DOM molecules. Light absorption and fluorescence intensity decreased by 34.5% and 15.3%, respectively. Molecular‐level analysis revealed that compounds with high molecular weight, high aromaticity, and low polarity were preferentially removed. Certain smaller species, such as lipids and unsaturated hydrocarbons, also exhibited a decline, but the scavenging effect of snowfall primarily targets larger DOM molecules with more complex structures, longer carbon chains, and higher heteroatom content. After snowfall, the DOM content in TSP increased again within one day and in some cases reached or exceeded pre‐snowfall levels. The post‐snowfall DOM tended to be enriched in complex, highly oxidized compounds with elevated molecular weight and double bond equivalence. The molecular characteristics were correlated with those of the molecules removed during snowfall. These results highlight snowfall's dual role in cold environments: it can temporarily reduce atmospheric organic matter, while also shaping short‐term DOM variability after the event.
Mu et al. (Thu,) studied this question.