Source and sink of volatile organic compounds over snow surface

Snow can serve as both a source and a sink for atmospheric volatile organic compounds (VOCs), as well as a surface for their oxidation. However, the influence of snow on the distribution and fate of VOCs at the surface level remains largely unclear. To address this, we conducted a field campaign in a suburban site of Northeast China, from January to March 2024. VOCs were collected using sorbent cartridges at three different heights (i.e., 2.2 m above snow, at snow surface, and 0.1 m below snow surface), over five daily time intervals, including 7:00 to 10:00, 10:00 to 13:00, 13:00 to 16:00, 16:00 to 19:00, and 19:00 to 7:00 the following day. A total of 48 VOCs, out of 89 in the standards, were detected and quantified due to their relatively low concentrations. These included 16 alkanes, 3 alkenes, 14 aromatics, and 15 halogenated hydrocarbons, measured using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Alkanes and aromatics were the most abundant VOC species, exhibiting a diurnal pattern with lower concentrations during the day and higher concentrations at night. The vertical profiles of VOCs indicated that snow could serve as a source for certain species, such as monoterpenes, and as a sink for others, such as aromatics. The corresponding emission rates and deposition velocities were calculated. The findings from this study enhance the understanding of snow-atmosphere interactions and provide critical insights into the role of snow in influencing surface-level VOC distributions and their associated atmospheric processes.