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新冠疫情期间武汉空气质量变化的多维观测分析

Multidimensional Observation Analysis of the Air Quality Changes in Wuhan during the Coronavirus Disease-2019 Pandemic

  • 摘要: 基于国控站点和武汉本地加密站点,利用2020年1月1日至2月13日6种常规污染物及细颗粒物(PM2.5)组分的逐小时监测数据,评估了新冠疫情管控前后武汉地区大气污染物的时空变化特征及管控措施对不同类型站点的影响区别。结果显示:在实施疫情管控措施后,武汉市颗粒物浓度大幅降低,基于两种观测网(89个站点)计算得出PM2.5、PM10浓度变化率分别为−23.44%、−32.95%,但O3浓度显著增加,变化率为55.22%,比国控站点变化率高10.6%;在空间分布上,颗粒物浓度呈现北高南低,但武汉偏南区域站点的浓度下降幅度更大,与偏南风频次增高导致管控措施更多影响下风方向区域有关。偏南区域站点NO2浓度降低幅度更大,同时O3浓度升高,其原因是NO浓度大幅降低,其滴定反应减弱,并且气象条件也有利于O3持续累积,维持较高浓度。从不同类别站点浓度变化差异来看,疫情管控措施对二次污染物的交通站点和工业园区站点影响最大,两者基于两种观测网计算所得的浓度变化率均超过国控站点的浓度变化率,PM2.5和O3的国控站点变化率分别比交通站点变化率低6%和18%。对于一次污染物而言,SO2、CO浓度变化小,浓度变化率分别为−6.10%和−5.61%,与疫情期间重点排放源没有停工有关;在6种常规污染物中,NO2浓度变化幅度最大,其浓度下降了−55.26 %,与交通管控直接相关。对比分析2019年和2020年同期气溶胶组分浓度发现,2020年疫情管控期间 \mathrmN\mathrmO_3^- / \mathrmS\mathrmO_4^2- 比值降低,更接近1,有机碳(OC)与元素碳(EC)比值增大到6.07,说明汽车尾气等移动源的比重减小,燃煤燃烧影响比重增大。

     

    Abstract: Based on the state-controlled sites and local-controlled sites, using the hourly monitoring data of six conventional pollutants and PM2.5 component data from 1 January to 13 February 2020, the temporal and spatial variation characteristics of air pollutants in the Wuhan area before and after the coronavirus disease 2019 (COVID-19) controls and the impact of control measures at different types of sites were evaluated. The results showed that after implementing epidemic control measures, the particulate matter concentration in Wuhan decreased significantly. Based on the calculation of two observation networks (89 stations), the change rates of PM2.5 and PM10 concentrations were −23.44% and −32.95%, respectively, but the O3 concentration increased significantly, at a rate of 55.22%, 10.6% higher than that of the state-controlled sites. In terms of the spatial distribution, the particulate matter concentration is higher in the north and lower in the south but decreases more at stations in south Wuhan, which is related to the increased frequency of southerly wind, resulting in more control measures affecting the downwind area. The decrease in NO2 concentration at the stations in the south is greater, while the O3 concentration increases. The reason is that as the NO concentration decreases greatly, the titration reaction weakens, and the meteorological conditions are also conducive to continuously accumulating O3 and maintaining a high concentration of O3. From the difference in concentration change among different types of stations, the epidemic control measures have the greatest impact on secondary pollutants at traffic and industrial stations. The concentration change rates calculated based on the two observation networks exceed those of state-controlled stations. The change rates of PM2.5 and O3 are 6% and 18% lower at state-controlled stations compared to traffic stations, respectively. The primary pollutants, SO2 and CO, show small concentration changes at rates of −6.10% and −5.61%, respectively, possibly because key emission sources were not shut down during the epidemic. Among the six conventional pollutants, the NO2 concentration changed the most, decreasing by −55.26%, which is directly related to traffic control. Comparing and analyzing the aerosol component concentrations in the same periods in 2019 and 2020 reveals that during the epidemic control period in 2020, the \mathrmN\mathrmO_3^- / \mathrmS\mathrmO_4^2- ratio decreased closer to 1, and the OC/EC ratio increased to 6.07, indicating a decrease in the proportion of mobile sources, such as automobile exhaust, and an increase in the impact of coal combustion.

     

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