This study by L.Liu et al. provides a year-long view of submicron aerosols during the 2019 JULIAC campaign in Jülich, Germany. The results show that nighttime chemistry plays a much larger role in organic aerosol formation than previously recognized.
Using constrained source apportionment with the ME-2 solver in SoFi, the team analyzed organic and nitrate signals together and clearly separated a distinct nighttime oxidized organic aerosol factor from bulk aerosol measurements. This nighttime component differs from daytime aerosol and makes a major contribution to secondary organic aerosol, especially in the cold season. The findings show that nitrate radicals drive the formation of low-volatility products at night. In winter, this process is mainly linked to biomass-burning emissions, while in summer it is driven more by biogenic emissions.
Overall, the study demonstrates how SoFi can reveal important chemical processes that would otherwise remain hidden in bulk aerosol data.