Central Department of Environmental Science, Tribhuvan University, Kathmandu, Nepal.
Department of Environmental Science, Patan Multiple Campus, Tribhuvan University, Lalitpur, Nepal.
Environ Monit Assess. 2023 Oct 18;195(11):1337. doi: 10.1007/s10661-023-11949-5.
The COVID-19 pandemic caused a setback for Nepal, leading to nationwide lockdowns. The study analyzed the impact of lockdown on air quality during the first and second waves of the COVID-19 pandemic in the Kathmandu Valley. We analyzed 5 years of ground-based air quality monitoring data (2017-2021) from March to July and April to June for the first and second wave lockdowns, respectively. A significant decrease in PM (particulate matter with an aerodynamic diameter ≤ 2.5 μm) concentrations was observed during the lockdowns. The highest rate of decline in PM levels was observed during May and July compared to the pre-pandemic year. The PM concentration during the lockdown period remained within the WHO guideline limit and NAAQS for the maximum number of days compared to the lockdown window in the pre-pandemic years (2017-2019). Likewise, lower PM levels were observed during the second wave lockdown, which was characterized by a targeted lockdown approach (smart lockdown). We found a significant correlation of PM concentration with community mobility changes (i.e., walking, driving, and using public transport) from the Spearman correlation analysis. Lockdown measures restricted human mobility that led to a lowering of PM concentrations. Our findings can be helpful in developing urban air quality control measures and management strategies, especially during high pollution episodes.
新型冠状病毒肺炎疫情给尼泊尔带来了挫折，导致全国范围内实行封锁。本研究分析了 COVID-19 大流行第一波和第二波期间封锁对加德满都谷地空气质量的影响。我们分析了 5 年来（2017-2021 年）从 3 月到 7 月和 4 月到 6 月的地面空气质量监测数据，分别用于第一波和第二波封锁。在封锁期间，PM（空气动力学直径≤2.5μm 的颗粒物）浓度显著下降。与大流行前一年相比，在 5 月和 7 月，PM 水平的下降速度最快。与大流行前几年（2017-2019 年）的封锁期相比，封锁期间 PM 浓度在大多数天数内均保持在世界卫生组织指导限值和 NAAQS 范围内。同样，在第二波封锁期间也观察到 PM 水平较低，这一封锁具有针对性（智能封锁）。从 Spearman 相关分析来看，我们发现 PM 浓度与社区流动性变化（即步行、驾驶和使用公共交通）之间存在显著相关性。封锁措施限制了人类的流动性，导致 PM 浓度降低。我们的研究结果可以帮助制定城市空气质量控制措施和管理策略，特别是在高污染时期。
