Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change, Nanjing University of Information Science and Technology, Nanjing, 210044, China; Key Laboratory Meteorological Disaster, Ministry of Education & Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disaster, Nanjing University of Information Science and Technology, Nanjing, 210044, China; Jiangsu Provincial Key Laboratory of Agricultural Meteorology, School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing, 210044, China.
Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change, Nanjing University of Information Science and Technology, Nanjing, 210044, China; Key Laboratory Meteorological Disaster, Ministry of Education & Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disaster, Nanjing University of Information Science and Technology, Nanjing, 210044, China; Jiangsu Provincial Key Laboratory of Agricultural Meteorology, School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing, 210044, China.
Environ Pollut. 2021 Apr 15;275:116615. doi: 10.1016/j.envpol.2021.116615. Epub 2021 Jan 29.
To prevent spreads of Coronavirus disease-2019 (COVID-19), China adopted the lockdown measures in late January 2020, providing a platform to study the response of air quality and atmospheric chemical and physical properties to strict reduced emissions. In this study, the continuous measurements of aerosol light absorption were conducted in Nanjing, east China, from January 3 to March 31, 2020. Our results showed that the contribution of black carbon (BC) to light absorption at the different wavelengths was more than 75% and the rest light absorption was contributed by brown carbon (BrC), which was mainly originated from primary emissions. Secondary BrC absorption, which was mainly produced by photochemical oxidation, constituted a minor fraction (2-7%) of the total absorption. Compared with the sampling in the pre-lockdown, the significant decreases of BC (43%) and secondary BrC absorption (31%) were found during the lockdown period, resulting in a substantial decrease of solar energy absorbance by 36% on a local scale. The control measures also changed the diurnal variations of light absorption. Due to the reduced emissions, the relative fraction of fossil fuel to BC also dropped from 78% in the pre-lockdown to 71% in the lockdown. The concentrations of BC, PM and NO decreased 1.1 μg m, 33 μg m and 9.1 ppb whereas O concentration increased 9.0 ppb during the COVID-19 lockdown period. The decreased concentrations of BC, PM and NO were mainly contributed by both emission reduction (51-64%) and meteorological conditions (36-49%). Our results highlighted that the balance of control measures in alleviation of particulate matter (PM) and O pollution, and meteorology should be seriously considered for improvement of air quality in this urban city of China.
为了防止 2019 年冠状病毒病（COVID-19）的传播，中国于 2020 年 1 月下旬采取了封锁措施，为研究空气质量和大气化学及物理特性对严格减排的响应提供了平台。在这项研究中，2020 年 1 月 3 日至 3 月 31 日，在中国东部的南京进行了气溶胶光吸收的连续测量。我们的结果表明，黑碳（BC）对不同波长光的吸收贡献超过 75％，其余的光吸收由棕色碳（BrC）贡献，而棕色碳主要来自一次排放。二次 BrC 吸收主要由光化学氧化产生，占总吸收的一小部分（2-7％）。与封锁前的采样相比，封锁期间发现 BC（43％）和二次 BrC 吸收（31％）的显著减少，导致局部太阳能吸收减少了 36％。控制措施还改变了光吸收的日变化。由于排放量减少，化石燃料在 BC 中的相对比例也从封锁前的 78％降至封锁期间的 71％。封锁期间，BC、PM 和 NO 的浓度分别降低了 1.1μg/m、33μg/m 和 9.1ppb，而 O 的浓度增加了 9.0ppb。BC、PM 和 NO 的浓度降低主要是由于减排（51-64％）和气象条件（36-49％）的共同作用。我们的研究结果强调，在中国这个城市，为改善空气质量，应认真考虑控制措施在缓解颗粒物（PM）和 O 污染方面的平衡以及气象条件的影响。
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