摘要
新冠疫情“封锁”为研究极限减排对环境空气污染物浓度变化的影响建立了“天然实验室”。本文通过多尺度对比贵阳市“封锁”前后不同阶段的空气污染物PM2.5,PM10,SO2,NO2,CO和O3浓度变化,并结合同期的气象资料,研究疫情“封锁”对贵阳市空气质量的影响。结果显示:“封锁”对6项污染物的影响明显不同,一级“封锁”导致PM2.5、PM10、SO2、NO2和CO平均浓度分别比“封锁”前期下降了3.23%、14.84%、0.08%、52.45%和22.30%,而O3平均浓度则上升了33.88%。NO2对疫情“封锁”的响应最为明显,其浓度大幅下降与疫情期间严格的交通管制有关。机动车活动水平下降减少了空气中的NO浓度,导致对O3的“滴定”作用减弱,从而使一级“封锁”期间O3浓度大幅上升。PM2.5平均浓度在一级“封锁”期间下降幅度较小,可能与气体–颗粒转换生成更多的硫酸盐气溶胶有关。气象条件对污染物浓度具有重要影响。在二级“封锁”期间日照时数和温度显著上升,相对湿度明显下降,光化学反应较为活跃,导致O3浓度显著上升。日照时数增加,气温升高使扬尘作用加强,导致空气中的颗粒物PM2.5和PM10浓度明显增大。本研究的启示为:采取减排措施改善空气质量时有必要制定预防O3污染的方案,并关注气体–颗粒转换产生的二次气溶胶对空气质量的影响。
The “lockdown” during the COVID-19 pandemic has established a “natural laboratory” to study the impact of extreme emission reductions on changes in air pollutant concentrations. We compared the changes in the concentrations of the pollutants PM2.5, PM10, SO2, NO2, CO and O3 at different stages before and after the “lockdown” in Guiyang city on a multi-scale basis. The results show that the “lockdown” had significantly different effects on the six pollutants. The first-level “lockdown” caused the average concentrations of PM2.5, PM10, SO2, NO2, and CO to drop by 3.23%, 14.84%, 0.08%, 52.45% and 22.30%, respectively, compared with the previous period of the “lockdown”. while the average concentration of O3 increased by 33.88%. NO2 had the most obvious response to the “lockdown” of the epidemic, and its sharp drop in concentration was related to strict traffic control. The reduction in the activity level of motor vehicles reduced the NO concentration in the air, causing the weakness of the “titration” of O3, which greatly increased the O3 concentration during the first-level “lockdown” period. The average concentration of PM2.5 decreased slightly during the first-level “lockdown” period, which may be related to the formation of more sulfate aerosols from gas-particle conversion. Meteorological conditions have an important influence on the concentration of pollutants. During the secondary “lockdown” period, the sunshine hours and temperature increased significantly, the relative humidity decreased significantly, and the photochemical reaction was more active, leading to a significant increase in the O3 concentration. The increasing sunshine hours and temperature had strengthened the effect of dust, resulting in a significant increase in the concentration of particulate matter PM2.5 and PM10 in the air. The enlightenment of this study is: it is necessary to formulate a plan to prevent O3 pollution, and pay attention to the impact of secondary aerosols produced by gas-particle conversion on air quality when adopting emission reduction measures to improve air quality.
