Emerging Amines in the Atmosphere: Occurrence and Potential Relevance to Carbon Capture

With the progress of global climate actions, amine-based carbon capture technology is being rapidly deployed. However, they potentially emit amines into the atmosphere, posing risks to air quality, climate, and human health. In this study, we conducted atmospheric measurements in Beijing during 2024 using Vocus Proton-Transfer-Reaction Mass Spectrometry. Several emerging amines of potential carbon capture relevance including C2H7NO, C4H10N2, C4H11NO, C4H11NO2, C5H13NO2 were identified in urban atmosphere. Their median mixing ratios range from 0.69 to 5.21 pptv, comparable to those of typical atmospheric alkylamines. They have different diurnal patterns in comparison to those of alkylamines (e.g., C2-amines). The presence of their oxidation products identified in laboratory studies was verified in the atmosphere, including C4H8N2 (tetrahydropyrazine) that is a potential indicator for C4H10N2 (piperazine) oxidation in the atmosphere. To further support these findings, a modified Orbitrap mass spectrometer was deployed at the same site in 2025 and its high resolution allowed for unambiguous identification of these amine peaks. Flue gas samples from a pilot carbon capture facility were also analyzed using the same Vocus instrument and confirmed the detection of C4H10N2, C4H11NO and C4H11NO2. In recent years, multiple carbon capture facilities have been deployed in Beijing and its surrounding areas. Backward-trajectory analysis of air masses suggests their potential influence to the site.