With the spread of the COVID-19 virus globally, cities worldwide have implemented unprecedented social distancing policies to mitigate infection rates. Many studies have demonstrated that improved air quality and reduced carbon emissions have resulted from the COVID-19 pandemic. Yet, questions remain regarding changes in atmospheric CO₂ concentrations because of the complex cycles involving the interaction of CO₂ with the natural environment. In this study, we compared the changes in urban CO₂ enhancement (△CO₂) reflecting the contribution of local CO₂ emissions to the atmospheric CO₂ in urban areas, according to the intensity of social distancing policies implemented during the COVID-19 pandemic in Seoul, South Korea. We used data from three CO₂ ground observation sites in the central area of Seoul and outside the urban area of Seoul. By comparing the urban CO₂ concentration in Seoul with that of the background area using two different methods, considering both vertical and horizontal differences in CO₂ concentration, we quantified the △CO₂ of the pre-COVID-19 period and two COVID-19 periods, during which intensive social distancing policies with different intensities were implemented (Level 1, Level 2.5). During the pre-COVID-19 period, the average △CO₂ calculated using the two methods was 24.82 ppm, and it decreased significantly to 16.42 and 14.36 ppm during the Level 1 and Level 2.5 periods, respectively. In addition, the urban contribution of Seoul to atmospheric CO₂ concentration decreased from 5.27% during the pre-COVID-19 period to 3.54% and 3.19% during the Level 1 and Level 2.5 periods, respectively. The results indicate that the social distancing policies implemented in Seoul resulted in reduced local CO₂ emissions, leading to a reduction in atmospheric CO₂ concentration. Interestingly, it also shows that the extent of atmospheric CO₂ concentration reduction can be greatly affected by the intensity of policies. Our study suggests that changes in human activity could reduce the urban direct contribution to the background CO₂ concentration helping to further mitigate climate change.

随着 COVID-19 病毒在全球的传播，世界各地的城市都实施了前所未有的社会疏远政策，以降低感染率。许多研究表明，COVID-19 大流行改善了空气质量并减少了碳排放。然而，由于涉及 CO ₂与自然环境相互作用的复杂循环，关于大气 CO ₂浓度变化的问题仍然存在。在本研究中，我们比较了反映本地 CO ₂排放对大气 CO ₂贡献的城市 CO ₂增强（△CO ₂）的变化在城市地区，根据韩国首尔 COVID-19 大流行期间实施的社会疏远政策的强度。我们使用了来自首尔市中心和首尔市区外三个 CO ₂地面观测站的数据。通过使用两种不同的方法比较首尔的城市 CO ₂浓度与背景区域的 CO ₂浓度，同时考虑到 CO ₂浓度的垂直和水平差异，我们量化了COVID-19 前时期和两个 COVID-19 时期的△CO ₂期间，实施了不同强度的密集社会疏远政策（级别 1，级别 2.5）。在 COVID-19 之前的时期，平均 △CO ₂两种方法计算得出的浓度为 24.82 ppm，在 1 级和 2.5 级期间分别显着下降至 16.42 和 14.36 ppm。此外，首尔城市对大气 CO ₂浓度的贡献从 COVID-19 之前的 5.27% 分别下降到 1 级和 2.5 级期间的 3.54% 和 3.19%。结果表明，首尔实施的社会疏远政策导致当地 CO ₂排放量减少，从而导致大气 CO ₂浓度降低。有趣的是，它还表明大气 CO ₂集中度降低会受到政策强度的很大影响。我们的研究表明，人类活动的变化可以减少城市对背景 CO ₂浓度的直接贡献，有助于进一步缓解气候变化。