● As soon as the cold wave goes away, fine dust...

As for the annual average concentration, the lowest ever



cold wave went away for a while, and fine dust arrived immediately after the day broke.

Yesterday (22nd), the concentration of ultrafine dust in Seoul rose to 52µg/m³ and in Gyeonggi-do to 56µg/m³, which was twice as high as usual.

Even today, the concentration of fine dust in western regions such as the metropolitan area, Chungcheong, and Jeonbuk is expected to show'bad' levels throughout the day.



However, it is highly likely that the concentration of ultrafine dust nationwide this year will hit a record low.

In the case of Seoul, the concentration of ultrafine dust began to be monitored in earnest from October 2013.

The concentration of ultrafine dust in Seoul, which was 26µg/m³ in 2014, peaked at 27µg/m³ in 2017, and did not decrease significantly to 24µg/m³ last year.

But this year, things are definitely different.

Although there is still about a week left this year, the concentration of ultrafine dust in Seoul measured so far is 20µg/m³, the lowest level since observation.



The reason for this decrease in concentration this time, as you might think, has been found to have a large impact on the decrease in social activity caused by corona.




Cause of fine dust reduction ① Corona 71% ② Weather 16% ③ Government policy 13%



Due to Corona 19, various social and economic activities in China and Korea have declined.

Particularly in February and March, when fine dust is at its worst, China enforced movement restrictions at the level of city blockade, and some factories were shut down.

Airplanes and ships with high emissions of air pollutants have also decreased more than usual.



Ajou University research team analyzed the amount of fine dust reduction caused by corona during the period.

In particular, we paid attention to February-March this year, when fine dust was the most severe and extreme measures due to corona were implemented.

The average concentration of fine dust in Korea from February 2017 to March 2019 was 32.8µg/m³, but this year it was found to have decreased by 9.9µg/m³ to 22.9µg/m³.



When the research team analyzed the reason for the reduction of fine dust through air quality simulation, 71% of the 9.9 µg/m³ reduction, or 7.0 µg/m³, was analyzed as a reduction due to Corona 19.

The concentration of fine dust decreases when the wind blows strongly or the East wind, which is less influenced by China, decreases. The reduction due to such weather was analyzed to be 1.6µg/m³, or 16%.

The reduction due to the seasonal management system and government policy was 13%.

It is said that the reduction of fine dust by 1.3µg/m³ due to the suspension of the operation of old coal-fired power plants, restrictions on the operation of old cars, the seasonal fine dust management system, including the two-part vehicle system, and Korea's long-term pollutant reduction policy.



In the same way, the research team also analyzed the situation in China.

The concentration of fine dust in China has decreased by 16.8µg/m³, which is more than ours, with 53% of corona-related effects, 22% of weather-related effects, and 25% of reduction policies.



It is worth noting that both China and Korea have significantly reduced the amount of fine dust caused by corona compared to the amount of reduction caused by the existing government policy.

To maintain the air quality this year, much stronger measures are needed than the current policy.

Corresponding author Kim Soon-Tae of the study said, "Even though we were able to confirm the unprecedented effect of improving air quality due to the spread of Corona 19, efforts to reduce emissions should be expanded more than now in order to obtain the clean air we want."



The study was published on December 17th in the sister magazine of Nature, a world-renowned academic journal, Scientific Reports.




● The reason why the reduction of fine dust in Korea is small compared to the amount of reduction in China.



Recent studies at home and abroad raise a question.

The average concentration of fine dust is higher in China than in Korea, but the reduction rate of fine dust is much faster in China.

As a result of the analysis of the Ajou University team, between 2015 and 2018, the amount of ultrafine dust in China decreased by 25%, whereas in Korea, it decreased by only 12%.

It was analyzed that half of the 12% declined due to the help of the weather.

The reduction in our efforts is about 6%.



As compared to China, the reason why the reduction efforts do not work well is because of the large amount of'nitric acid' coming from China and too much'ammonia' in the domestic atmosphere, a study found.

The research team analyzed the air quality of Baengnyeong Island, which has no emission source, so the air is clean and the impact of Chinese pollutants is well observed.

As a result, it was confirmed that the fine dust of sulphate mainly produced by coal power plants on Baengnyeong Island decreased.

However, the nitrate fine dust was rather increased.

Nitrate fine dust is the conversion of'nitrogen oxide', which is mainly made in automobiles, into fine dust.

'Nitrogen oxide' are replaced by 'nitrate' Meet and water in the atmosphere, nitric acid, ammonia, and the encounter will be "fine dust" that we know of. (The nitrate fine particles)



to the coal consumption reduced by intensive policies of China Although the amount of sulfuric acid transferred to Korea decreased, the amount of nitrate fine dust increased as the excess of ammonia that had reacted with sulfuric acid reacted with'nitric acid' transferred from China.

Nitrogen oxide and nitric acid coming from China meet with Korea's ammonia to generate additional fine dust, so Korea's reduction efforts are not working properly.



We cannot reduce the material coming from China.

If so, reducing domestic ammonia will likely solve it, but the problem is that the concentration is too high and it is very difficult to reduce it.

According to the data from the Ministry of Environment compiled up to the most recent, Korea's ammonia emissions amounted to 230,000 tons in 2001 and 300,000 tons in 2017, which is actually increasing.

During the same period, the emission of nitrogen oxides decreased slightly from 1.21 million tons to 1.18 million tons, but the ammonia emission increased.




Korea's ammonia emissions are around 308,000 tons per year, of which ammonia from agriculture accounts for 79% of the total.

Ammonia occurs frequently when fertilizers are used or when raising livestock, but there is no way to control it, so there is a limit to reducing it because pollutants are not emitted from one place like factory chimneys, but rather spread widely.

Because the ammonia concentration is so high, some analysis suggests that a slight reduction in ammonia will not reduce fine dust at all.



Due to these difficulties, fine dust, which has been a social problem since 2013, is still not resolved.

However, while experiencing the corona crisis, I certainly saw great potential.

Until now, there was a limit to reducing pollutants, but if the emission of pollutants is drastically reduced, fine dust decreases faster than expected.

The social distancing and activity restrictions caused by the corona are causing tremendous damage, but it was a year when we were able to see to what extent we had to limit our activities to reduce fine dust.

Like Corona, it suggests that catching fine dust requires much more sacrifice than it is now.



(Photo = Yonhap News)



※Reference


-The impacts of COVID‑19, meteorology, and emission control policies on PM2.5 drops in Northeast Asia, YoonHee Kang


-Direct and cross impacts of upwind emission control on downwind PM2.5 under various NH3 conditions in Northeast Asia, Eunhye Kim


-Role of emissions and meteorology in the recent PM2.5 changes in China and South Korea from 2015 to 2018, Minah Bae


-National Fine Dust Information Center