Fine dust has hit the country from Sunday when a cold spell subsided. Fine dust density in the Greater Seoul region and North Chungcheong region was forecast to remain at the “bad” level through Wednesday.
According to the National Institute of Environmental Research Sunday, fire dust density in the western central region of the Korean Peninsula including Seoul, Gyeonggi and North Chungcheong provinces stood at the “bad” level on the day. The daily average ultrafine dust density in Seoul was 45 microgram (microgram or μg is one 1 millionth of a gram) per cubic meters as of 3 p.m. on the day. The reading of ‘bad’ in ultrafine dust density ranges from 36 μg to75 μg. The density hit 98 μg and 91 μg, respectively, in Dongducheon in northern Gyeonggi and Danyang in North Chungcheong at some moments in the morning, exceeding the “very bad” (75 μg or higher) level. “Due to stagnant atmosphere, pollutants generated within the country did not flow away, elevating fine dust density levels,” the institute said.
When cold Siberian high atmospheric pressure transforms into migratory anticyclone to affect the nation, the weather gets less cold, but the atmosphere gets stagnant, blocking pollutants from flowing away. For this reason, the country comes to experience the so-called ‘three cold days followed by four fine dust days’ phenomenon, in which air quality improves on cold days before deteriorating on warmer days.
The institute forecast that fine dust density levels will remain high particularly in the Greater Seoul region through Wednesday. It forecasts ultrafine dust levels in the Greater Seoul and Chungcheong regions will be “high.” The reading of “high” in weekly forecast represents a daily average of 36 μg or higher, and is equivalent to “bad” and “very bad” in daily forecast. Notably, high fine dust levels will likely increase further due to fine dust flowing in from overseas beginning Tuesday. “Fine dust density could rise to the “very bad” level due to smog from China around Tuesday,” Ban Ki-seong, head of the forecast center at K Weather.