Hua Nan, Shang Yue, Xie Ming-Jie
Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science & Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China.
Shangqiu Meteorological Bureau, Shangqiu 476000, China.
Huan Jing Ke Xue. 2023 Feb 8;44(2):593-601. doi: 10.13227/j.hjkx.202204103.
To understand the changes in chemical composition and sources of PM under the extreme reduction background during the COVID-19 epidemic periods in Nanjing, hourly observation results of PM components (water-soluble inorganic ions, carbonaceous components, and inorganic elements) of two epidemic events from January to March 2020 and June to August 2021 were analyzed. In comparison to that during pre-epidemic periods, the concentration of NO during the two epidemic control periods decreased by 52.9% and 43.0%, respectively, which was larger than the decreases in NH(46.4% and 31.6%) and SO(33.8% and 16.5%). Since the observation site was located close to a main road, the decrease in elemental carbon (EC, 35.4% and 20.6%) was higher than that in organic carbon (OC, 11.1% and 16.2%). In reference to the variations in the characteristic ratios of the bulk components mentioned above, the epidemic control showed a more substantial influence on traffic emissions than industrial activities. The concentration time series of PM major components over the epidemic periods indicated that NO from local traffic emissions had substantial contributions to the formation of NO, which led to local short-term PM pollution. In addition, the positive matrix factorization (PMF) model was used to analyze the hourly observation data of PM components. The seven identified factors were linked with metallurgy, firework and firecracker combustions, road traffic emissions, coal combustion, dust resuspension, secondary sulfate, and secondary nitrate. Because the nitrate was unstable under high temperature, the contribution of secondary nitrate to PM during the epidemic control period of 2021 (summer, 21.2%) was much lower than that during the epidemic control period of 2020 (winter, 60.6%); however, the formation of secondary components always dominated the contribution of PM sources. Therefore, emissions of NO and SO should be further controlled to continuously reduce ambient PM concentrations in Chinese cities.
为了解南京新冠疫情期间极端减排背景下细颗粒物（PM）的化学组成和来源变化，分析了2020年1月至3月以及2021年6月至8月两次疫情期间PM成分（水溶性无机离子、碳质成分和无机元素）的逐小时观测结果。与疫情前相比，两个疫情防控期间的NO浓度分别下降了52.9%和43.0%，降幅大于NH（46.4%和31.6%）和SO（33.8%和16.5%）。由于观测点靠近主干道，元素碳（EC，35.4%和20.6%）的下降幅度高于有机碳（OC，11.1%和16.2%）。参照上述总体成分特征比值的变化，疫情防控对交通排放的影响比对工业活动的影响更大。疫情期间PM主要成分的浓度时间序列表明，本地交通排放的NO对NO的形成有很大贡献，导致了本地短期的PM污染。此外，采用正定矩阵因子分解（PMF）模型分析了PM成分的逐小时观测数据。识别出的七个因子与冶金、烟花爆竹燃烧、道路交通排放、煤炭燃烧、扬尘、二次硫酸盐和二次硝酸盐有关。由于硝酸盐在高温下不稳定，2021年疫情防控期间（夏季，21.2%）二次硝酸盐对PM的贡献远低于2020年疫情防控期间（冬季，60.6%）；然而，二次成分的形成始终主导着PM源的贡献。因此，应进一步控制NO和SO的排放，以持续降低中国城市的环境PM浓度。
