Significant Contribution of Algal Emissions to Secondary Organic Aerosol Formation from Ambient Air in a Eutrophic Lake-Adjacent Area, China

Eutrophic lakes, often enriched with various algae, can emit large amounts of volatile organic compounds into the atmosphere, which may serve as potential secondary organic aerosol (SOA) precursors. However, their contributions to SOA formation remain poorly understood. We herein conducted a real-time measurement of SOA formation from ambient air in the Taihu Lake-adjacent area in China during the summertime using an Oxidation Flow Reactor (OFR). The results showed that SOA formation in the OFR peaked at 2.62 ± 5.09 μg m –3 during daytime and 6.52 ± 8.02 μg m –3 during nighttime under equivalent photochemical ages of 2 and 3.3 days, respectively. Known precursors explained 23.8%–30.5% of the measured SOA, suggesting the importance of unidentified precursors in the Taihu Lake-adjacent area. Furthermore, by combining the positive matrix factorization and multilinear regression, we found that algal emissions contributed 17.7% and 6.4% to the potential SOA during daytime and nighttime. Heatwaves further enhanced the contribution of algal emissions to SOA, which can exceed 30% for temperatures over 35 °C. To the best of our knowledge, this is the first time that the contribution of algal emissions to SOA formation near a eutrophic lake was quantified. These findings highlight the critical role of algal emissions in SOA formation in adjacent areas of aquatic ecosystems.