Abstract Aerosol size distributions were measured using a scanning mobility particle sizer (SMPS), and also PM1 (particulate matter ≤ 1 μm in aerodynamic diameter) samples were collected in parallel at a representative site in New Delhi during spring in 2013 and 2014. Based on the temporal variation of particle count mean diameter (CMD), sampling periods are characterized as growth events and non-growth events. Particle size distribution measurements suggest that some consecutive nights experienced unique nighttime subsequent growth of particles, which sustained for a longer period. Average particle growth rate measured during growth events was 5.64 ± 3.03 nm h−1. Atmospheric trace gas concentrations and meteorological data show that these growth events (nighttime) are influenced by higher concentrations of gases, e.g., NO2 (56.5 ± 29.7 μg m−3), SO2 (9.34 ± 1.14 μg m−3) and RH (45.7 ± 9.5%) than those of non-growth events (daytime) (37.9 ± 18.6 μg m−3, 7.19 ± 2.08 μg m−3 and 37.7 ± 6.9%, respectively). Further, analysis of PM1 samples collected during the study period shows that the particulate water-soluble organic carbon (WSOC) (12.7 ± 4.1 μg m−3), NH4+ (9.4 ± 3.2 μg m−3), SO42− (2.03 ± 0.70 μg m−3), K+(1.06 ± 0.40 μg m−3), and NO2− + NO3− (0.59 ± 0.36 μg m−3) are the major contributors of particulate mass, wherein NH4+, SO42−, K+, NO2− + NO3− mass concentrations were higher during growth events. Correlation study shows that nighttime aerosol composition during growth (in sub-micron range) events are more enriched by inorganic species (i.e., NH4NO3, (NH4)2SO4 and H2SO4 vapors) as compared to organics (i.e., WSOC, does not show much difference in growth events and non events). Our results suggest that nighttime sulfate formation at the site is mostly mediated by high NO2 and NH3 at elevated RH. For the formation of sulfate and other inorganic species, a nighttime atmospheric chemistry is proposed, which is linked to particle growth. Growth events observed typically in nighttime have both biomass burning and anthropogenic influences as indicated by high concentrations of WSOC, K+ and black carbon in PM1 and carbon monoxide in gas phase.

中文翻译：

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在新德里春季观察到的夜间颗粒生长：SO 2 水相氧化的证据

摘要 使用扫描迁移率粒度仪 (SMPS) 测量气溶胶粒径分布，并于 2013 年和 2014 年春季在新德里的代表性地点平行收集 PM1（空气动力学直径≤ 1 μm 的颗粒物）样本。粒子计数平均直径 (CMD) 的时间变化，采样周期被表征为生长事件和非生长事件。颗粒尺寸分布测量表明，一些连续的夜晚经历了独特的夜间颗粒随后生长，这种生长持续了更长的时间。在生长事件期间测量的平均颗粒生长率为 5.64 ± 3.03 nm h-1。大气痕量气体浓度和气象数据表明，这些生长事件（夜间）受到较高浓度气体的影响，例如 NO2 (56.5 ± 29.7 μg m-3)，SO2 (9.34 ± 1.14 μg m-3) 和 RH (45.7 ± 9.5%) 比非生长事件（白天）（37.9 ± 18.6 μg m-3、7.19 ± 2.08 μg m-3 和 37.7 ± 6.9%）分别）。此外，对研究期间收集的 PM1 样本的分析表明，颗粒状水溶性有机碳 (WSOC) (12.7 ± 4.1 μg m-3)、NH4+ (9.4 ± 3.2 μg m-3)、SO42- (2.03 ± 0.70 μg m-3)、K+(1.06 ± 0.40 μg m-3) 和 NO2- + NO3- (0.59 ± 0.36 μg m-3) 是颗粒质量的主要贡献者，其中 NH4+、SO42-、K+、NO2- + NO3- 质量浓度在生长事件期间更高。相关性研究表明，与有机物（即 WSOC）相比，生长（亚微米范围内）事件期间的夜间气溶胶成分更富含无机物种（即 NH4NO3、(NH4)2SO4 和 H2SO4 蒸气）在增长事件和非事件中）。我们的结果表明，该地点夜间硫酸盐的形成主要是由高 RH 下的高 NO2 和 NH3 介导的。对于硫酸盐和其他无机物种的形成，建议采用夜间大气化学，这与颗粒生长有关。通常在夜间观察到的生长事件同时具有生物量燃烧和人为影响，如 PM1 中高浓度的 WSOC、K+ 和黑碳以及气相中的一氧化碳所示。