School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, Republic of Korea.
Climate Research Department, National Institute of Meteorological Sciences, Seogwipo, Republic of Korea.
Sci Total Environ. 2023 Feb 1;858(Pt 2):159904. doi: 10.1016/j.scitotenv.2022.159904. Epub 2022 Nov 1.
Despite the curtailment of atmospheric condensing precursor gases during the Coronavirus disease 2019 (COVID-19) lockdown (LD) period, unexpected haze events via the formation of new particles and their subsequent growth have been identified. This study investigated the impact of emission reduction during the Chinese LD period on the new particle formation (NPF) frequency and corresponding particle number size distribution (PNSD) at three regional background atmospheric monitoring sites in the western coastal areas of the Korean Peninsula. During this duration, the number concentrations of the nucleation- (<25 nm) and accumulation-mode (>90 nm) particles significantly decreased in Baengryeong (BRY), showing decreases of 34% and 29%, respectively. Unlike BRY, the PNSD in Anmyeon (AMY), which is influenced by nearby industrial emissions, remained nearly unchanged during the LD period, possibly because the reduction in industrial emissions was not significant during the social distancing period enforced by Korea. Bongseong (BOS) showed a similar variation to that of BRY; however, the magnitude of the reduction was weaker because of its higher altitude compared to other sites. The cyclostationary empirical orthogonal function technique was applied to the measured PNSDs at the three sites to objectively classify NPF events. Because mode 1 of cyclostationary loading vectors commonly represented the typical diurnal variation of PNSD during regional NPF events at three sites, mode 1 of the corresponding principal component time series was used for NPF classification. The NPF frequency decreased by 7%, 1%, and 7% in BRY, AMY, and BOS, respectively, despite favorable meteorological conditions, such as increased temperature and insolation during the LD period. The diurnal variation in the sulfuric acid (HSO) proxy implied that the HSO proxy acted as a determining factor for NPF events during the NPF occurrence time (8-12 local hours) in AMY and BOS; however, NPF occurrence in BRY was not connected to the HSO proxy level. This suggests that BRY was more likely to be influenced by the reduction in organic species in the continental upwind regions, while the occurrence of NPF events in AMY and BOS can be suppressed in association with the distinct reduction in inorganic compounds represented by the HSO proxy during the LD period.
尽管在 2019 年冠状病毒病（COVID-19）封锁（LD）期间限制了大气冷凝前体气体的排放，但仍发现了通过新粒子的形成及其随后的生长而导致的意外霾事件。本研究调查了中国 LD 期间减排对朝鲜半岛西海岸三个区域背景大气监测站点新粒子形成（NPF）频率和相应粒子数浓度粒径分布（PNSD）的影响。在此期间，在 Bengryeong（BRY），小于 25nm 的成核模态和大于 90nm 的积聚模态粒子的数浓度显著降低，分别降低了 34%和 29%。与 BRY 不同，在受附近工业排放影响的 Anmyeon（AMY），PNSD 在 LD 期间几乎没有变化，这可能是因为在韩国实施社交距离期间，工业排放的减少并不显著。Bongseong（BOS）的变化与 BRY 相似；然而，由于其海拔较高，减少的幅度较弱。循环平稳经验正交函数技术被应用于三个站点的测量 PNSD，以客观地对 NPF 事件进行分类。由于循环平稳加载向量的模式 1通常代表三个站点区域 NPF 事件期间 PNSD 的典型日变化，因此使用相应主分量时间序列的模式 1进行 NPF 分类。尽管在 LD 期间的气象条件有利，例如温度升高和光照增加，但在 BRY、AMY 和 BOS，NPF 频率分别降低了 7%、1%和 7%。在 AMY 和 BOS 中，硫酸（HSO）代理的日变化表明 HSO 代理在 AMY 和 BOS 的 NPF 发生时间（当地时间 8-12 时）内是 NPF 事件的决定因素；然而，BRY 中的 NPF 发生与 HSO 代理水平无关。这表明 BRY 更可能受到大陆上风区有机物种减少的影响，而 AMY 和 BOS 中 NPF 事件的发生可以与 LD 期间 HSO 代理代表的无机化合物的明显减少有关。
