Oxidized Organic Aerosol (OOA), a major component of fine atmospheric particles, impacts climate and human health. Previous experiments and atmospheric models emphasize the importance of nocturnal OOA formation from NO₃· oxidation of biogenic VOCs. This seasonal study extends the understanding by showing that nocturnal oxidation of biomass-burning emissions can account for up to half of total OOA production in fall and winter. It is the first to distinguish nocturnal OOA characteristics from daytime OOA across all seasons using bulk aerosol measurements. Summer observations of nocturnal OOA align well with regional chemistry transport model predictions, but discrepancies in other seasons reveal a common model deficiency in representing biomass-burning emissions and their nocturnal oxidation. This study underscores the significance of near-ground nocturnal OOA production, proposes a method to differentiate it using bulk aerosol measurements, and suggests model optimization strategies. These findings enhance the understanding and prediction of nighttime OOA formation.

氧化有机气溶胶 (OOA) 是大气细颗粒物的主要成分，影响气候和人类健康。先前的实验和大气模型强调了NO ₃ · 生物VOC 氧化产生夜间OOA 的重要性。这项季节性研究扩展了我们的认识，表明生物质燃烧排放物的夜间氧化可占秋季和冬季 OOA 总产量的一半。它是第一个使用大量气溶胶测量来区分所有季节夜间 OOA 特征与白天 OOA 的技术。夏季夜间 OOA 的观测与区域化学传输模型的预测非常吻合，但其他季节的差异揭示了模型在代表生物质燃烧排放及其夜间氧化方面的常见缺陷。这项研究强调了近地夜间 OOA 产生的重要性，提出了一种使用大量气溶胶测量来区分它的方法，并提出了模型优化策略。这些发现增强了对夜间 OOA 形成的理解和预测。