On the contribution of low-molecular mass organic acids to new particle formation in a continental central European city

New particle formation (NPF) contributes substantially to the overall aerosol burden, impacting air quality, climate, and human health. This study investigates the roles of biogenic and anthropogenic molecules together with sulfuric acid in NPF and growth in Budapest, an urban environment in continental central Europe with diverse emission sources. Our findings highlight a strong role of sulfuric acid in nucleation, though additional species are necessary to explain the high observed formation rates. We find that regional NPF events are primarily associated with southerly air masses and elevated temperatures, which enhance the concentrations of precursor vapors. Among these, low-molecular-mass organic acids such as malonic and acetic acid exhibit strong correlations with particle formation rates and number concentrations, particularly at high concentrations, indicating their role in different NPF stages. Furthermore, we show that oxidized organic molecules (OOMs) from both biogenic and anthropogenic volatile organic compounds also play a role in NPF and growth. By classifying OOMs based on their source rather than volatility, we gain better insights into their roles. Our results suggest that isoprene and aliphatic OOMs promote nucleation, while terpenes and aromatic OOMs appear less involved. This study underscores the complexity of NPF in urban environments, where diverse chemical species interact under varying meteorological conditions. Our findings are crucial for refining atmospheric models and encourage informing strategies to mitigate air pollution and climate impacts.