2015-2021年南京市PM2.5和O3污染特征及复合污染个例研究
Pollution Characteristics and an Air Combined Pollution Case of PM2.5 and O3 in Nanjing from 2015 to 2021
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摘要: 为探究南京市PM2.5和臭氧(O3)污染特征,揭示PM2.5和O3复合污染过程中环境空气污染物及其10nm-10μm气溶胶粒径分布演变特征,分析了2015-2021年南京市环境空气污染物小时浓度数据,并对2015年10月12-17日典型复合污染个例进行了详细分析。结果表明:2015-2021年南京市不同大气污染物的变化特征不同。PM2.5、PM10和SO2浓度显著降低,年均下降率分别为8.9%/a、6.2%/a和15.4%/a。NO2在2015-2019年呈现增加趋势。CO在2016年达到峰值后开始进入下降周期,年均下降率为7.6%/a。2015-2021年O3浓度变化较小。南京市大气污染状况发生较大变化,由PM2.5为主导的大气复合污染转变为以O3为主导的大气复合污染。PM2.5污染频次和污染强度均显著降低,O3污染频次和污染强度均未发生显著变化。污染不同阶段气溶胶数浓度谱均为双峰型分布,但是峰值粒径和浓度存在较大差异。PM2.5污染阶段数浓度峰值浓度最低,NO2污染阶段数浓度谱第一个峰值的峰值粒径向小粒径段偏移,PM2.5和O3复合污染阶段数浓度谱第一个峰值粒径向大粒径段偏移。O3污染阶段,数浓度谱峰值粒径没有变化,但是峰值浓度显著增加,尤其是第一个峰值浓度,是污染前的3-5倍。污染不同阶段下不同环境空气污染物和不同模态气溶胶数浓度的日变化不同。Abstract: In order to explore the characteristics of PM2.5 and ozone (O3) pollution in Nanjing, and reveal the evolution characteristics of ambient air pollutants and 10nm-10μm aerosol size distribution during the PM2.5 and O3 combined air pollution, the hourly concentration data of ambient air pollutants was analyzed in Nanjing from 2015 to 202, and a detailed analysis of typical air combined pollution case from October 12 to 17, 2015. The results showed that the variation characteristics of different ambient air pollutants were different in Nanjing from 2015 to 2021. The concentrations of PM2.5, PM10 and SO2 were significantly decreased, with an average annual decrease rate of 8.9%/a, 6.2%/a and 15.4%/a, respectively. NO2 showed an increasing trend from 2015 to 2019. After reaching its peak in 2016, CO began to enter a decline trend, with an average annual decline rate of 7.6%/a. O3 concentration variation was small from 2015 to 2021. The air pollution situation had undergone great changes in Nanjing, and the air pollution dominated by PM2.5 pollution had transformed into the O3 pollution. The frequency and intensity of PM2.5 pollution decreased significantly, while the frequency and intensity of O3 pollution did not change significantly. The number concentration spectra of aerosols in different stages of the air combined pollution were bimodal, but the peak particle size and concentration were different. The peak concentration of size distribution was the lowest in the PM2.5 pollution stage, the peak of particle size distribution in the first peak shifted to the small particle size segment in NO2 pollution stage, and the first peak particle size shifted to the large particle size segment in the PM2.5 and O3 compound pollution stage. In the O3 pollution stage, the peak particle size of the number concentration spectra did not change, but the peak concentration increased significantly, especially the first peak concentration, which was 3-5 times than before the pollution. Under different pollution stages, the diurnal variations of the different ambient air pollutants and aerosol number concentration of different mode exhibited great variability.
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Key words:
- PM2.5 /
- O3 /
- air combined pollution /
- number concentration /
- size distribution
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