STATISTICALLY UPDATING PATTERN CHANGE OF NITROGEN DIOXIDE (NO2) POLLUTION IN SEOULSEOK HO CHANG AND SOONHUI LEE
Our previous study (Chang and Lee, 2022) presented observations on the recent changes in nitrogen dioxide (NO2) pollution of Seoul after the COVID-19 pandemic. This paper derives updated results by incorporating recent data, specifically data for the second half of 2021. In addition to confirming the extended results of the existing study (Chang and Lee, 2022), we derived more specific interpretations of the results. The results were as follows: (i) The average monthly NO2 concentration in Seoul has decreased significantly in 2020 compared to that before the COVID-19 pandemic; and (ii) the average difference in the monthly concentration of NO2 in Seoul between January 2021 to December 2021 period and that from January 2020 to December 2020 is not statistically significant. We also found the results originating partly from lifted restrictions on public transportation and non-road vehicles, and partly from resumption of suspended nonindustrial combustion plants in Seoul after the first half of 2020, complementing our previous findings in Chang and Lee (2022). Our study shows statistically comprehensive results compared to the studies that limit their discussions to average values, as that presented in a report by the Ministry of Environment, Republic of Korea.