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Peroxyacetyl nitrate (PAN) and ozone (O 3) are two typical indicators of photochemical pollution, which are harmful to human body and environment. In this study, PAN and O 3 were continuously monitored during static management (SM) of the COVID-19 epidemic in Zhengzhou. Briefly, SM refers to control policies in that all except for essential business are closed; work at home; and no people going out and no gathering, etc. During the SM, the temperature suddenly dropped from 26 °C to 14 °C, which provided a good experimental condition for the study of source transformation, accumulation, and consumption of PAN in the atmosphere. The concentrations of PAN were 0.6, 0.8, and 0.5 ppbv in three periods: before, during, and after the SM. During the SM, the lifetime of PAN was increased due to low temperature, and the accumulation time of PAN was longer, resulting in the increase of PAN concentration in daytime faster than the other two periods. During SM, especially after the temperature drops, the average atmospheric lifetime of PAN was 23.8 h, which was higher than 17.6 h before SM and 13.8 h after SM. This indicated that low temperature was more conducive to the accumulation of PAN. The high potential PAN source (CBPF>0.8) mainly came from the northeast of Zhengzhou, and the wind speed range was between 2.5 and 3 m/s. The backward trajectory analysis showed that 83.3% of the air mass from the northeast and northwest had a greater impact on the PAN concentration in Zhengzhou. [Display omitted] • The concentrations of secondary pollutants PAN and O 3 increased during the COVID-19 control period. • PAN is more likely to accumulate at low temperatures. • At high temperatures, PAN is more likely to pyrolysis and release PA radicals. • Northeast and northwest directions are the main source directions of PAN long-distance transmission. [ABSTRACT FROM AUTHOR]

As the main atmospheric pollutants, the nitrogen oxides (NO x) and dust from industrial exhaust have caused a series of environmental problems. Catalytic membrane is one of the most important technologies for integrated denitration and dust removal, which can achieve the efficient treatment of multiple pollutants. In order to achieve the simultaneous removal of NO and dust in low-temperature exhaust, a novel MnO x /TiO 2 /SiC catalytic membrane was developed. The using of TiO 2 aerogel as the transition layer could increase the loading capacity of MnO x by more than twice, but has little effect on gas permeance of SiC ceramic membrane. The MnO x /TiO 2 /SiC catalytic membrane also exhibit excellent filtration performance with dust rejection rate exceeding 99.97% and thus preventing adverse effects of dust on the catalyst. In the NO and dust coexistence system, the obtained catalytic membrane exhibits good catalytic activity owing to its high loading capacity and outstanding filtration performance, which lead to the high NO conversion rate above 80% with the temperature range of 120–180 °C. Meanwhile, the catalytic membrane exhibits remarkable stability in simulation environment, and the NO conversion rate could maintain at 90% within 65 h. The novel MnO x /TiO 2 /SiC catalytic membrane showed great promise for low-temperature exhaust gas purification. • When using TiO 2 aerogel, the loading capacity of MnO x increased by more than twice. • TiO 2 and MnO x exhibit little effect on gas permeance of SiC ceramic membrane. • The catalytic membrane exhibits superior catalytic and filtration performance. • In the NO and dust coexistence system, dust has no effect on catalytic activity. • The catalytic membrane exhibits remarkable stability in simulation environment. [ABSTRACT FROM AUTHOR]