To reduce and mitigate the concentration of PM2.5 in wintertime, “Fine particular matter management season” is carried out annually with additional emission abatement actions. To address air pollution, the Seoul Metropolitan Government implemented the second Fine particular matter management season for four months from December 2020 to March 2021. During the period, 13 PM2.5 mitigation plans were carried out and they comprised four sectors: transportation, commercial and residential heating, manufacturing workplace, and exposure to air pollution

The major action in the transportation regulation sector is to charge driving vehicles with emission-grade of tier-5 in the whole area of Seoul. Another action was the financial support for the emission grade of tier-5 vehicles to be replaced with vehicles having the higher emission grade or to be scrapped earlier. Considered the commercial and residential heating sector, the government subsidy for low-NOx residential boilers played an important role in replacing high-NOx boilers used in the residential area. And large commercial buildings were observed whether they kept the inner temperature to maintain appropriate energy consumption. Manufacturing workplaces and construction areas were intensively monitored to reduce fugitive dust emissions. For the sector of exposure to air pollution, cleaning of major vehicle roads was further implemented.

Of the 13 plans from the 2nd fine particular matter management season, 6 major plans were investigated to estimate the amount of emissions reduced. During the management season, 147.2 tons of primary PM2.5 emissions decreased, which is about 16.9% of Seoul's total primary PM2.5 emissions as of 2016. For instance, charging driving vehicles with the emission grade of tier-5 ended up decreasing 82 tons of primary PM2.5 emission, accounting for about 55% of the total reduction during the management season. Nitrogen oxides (NOx), one of the major precursors generating secondary PM2.5, decreased about 10% of the total NOx emissions in Seoul. Among the 6 major plans, charging driving vehicles with the emission grade of tier 5 was the most effective in terms of reducing both primary PM2.5 and NOx emissions.

It is found that the number of total tier-5 vehicles in South Korea has decreased, particularly those registered in Seoul, Incheon, and Gyeonggi-do, which comprise Seoul Metropolitan Area. When it comes to the tier-5 vehicles with low-emission treatment, the decreasing trend is more rapid in Seoul Metropolitan Area than that in other areas. We think that it is important to carry out the financial supports for the low-emission treatment with prohibiting driving vehicles without the low-emission treatment simultaneously.