| 2020~2021年新冠疫情期间南京市PM2.5化学组成与来源变化特征 |
| 摘要点击 3620 全文点击 2866 投稿时间：2022-04-09 修订日期：2022-05-14 |
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| 中文关键词 新冠疫情 PM2.5 化学组成 交通排放 源解析 |
| 英文关键词 COVID-19 PM2.5 chemical composition traffic emission source apportionment |
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| 中文摘要 |
| 为了解新冠疫情期间极端减排情景下南京市PM2.5的化学组成和来源变化，对南京市2020年1~3月和2021年6~8月两次疫情管控前后PM2.5化学组分（水溶性无机离子、碳质组分和无机元素）的小时观测结果进行分析.结果表明，NO3-浓度在两次疫情管控期间比管控前分别下降52.9%和43.0%，高于NH4+（46.4%和31.6%）和SO42-（33.8%和16.5%）.由于观测点位于交通干道附近，元素碳（EC）的下降幅度（35.4%和20.6%）高于有机碳（OC；11.1%和16.2%）.结合以上丰量组分特征比值的变化，推断疫情管控对交通排放的影响比工业活动更显著.各主要丰量组分浓度在疫情管控前后的连续变化过程表明，来自本地交通排放的NOx对PM2.5中NO3-的形成有重要贡献，并且是短期内本地PM2.5污染形成的重要原因.另外，还采用正定矩阵因子分解模型（PMF）分析PM2.5成分的小时观测数据，解析出的7个因子可分别代表冶金、烟花爆竹燃放、道路交通排放、燃煤、扬尘、二次硫酸盐和二次硝酸盐.由于在高温下硝酸盐不稳定，2021年疫情管控期间（夏季）二次硝酸盐对PM2.5的贡献（21.2%）远低于2020年疫情管控期间（冬季，60.6%），但二次组分的形成始终在PM2.5的来源贡献中占主导地位.因此，进一步控制NOx和SO2排放将是我国城市地区PM2.5持续下降的有效途径. |
| 英文摘要 |
| To understand the changes in chemical composition and sources of PM2.5 under the extreme reduction background during the COVID-19 epidemic periods in Nanjing, hourly observation results of PM2.5 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 NO3- during the two epidemic control periods decreased by 52.9% and 43.0%, respectively, which was larger than the decreases in NH4+(46.4% and 31.6%) and SO42-(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 PM2.5 major components over the epidemic periods indicated that NOx from local traffic emissions had substantial contributions to the formation of NO3-, which led to local short-term PM2.5 pollution. In addition, the positive matrix factorization (PMF) model was used to analyze the hourly observation data of PM2.5 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 PM2.5 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 PM2.5 sources. Therefore, emissions of NOx and SO2 should be further controlled to continuously reduce ambient PM2.5 concentrations in Chinese cities. |
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