[The Hwankyung Ilbo] Analysis on the causes of the high density of fine dust (PM2.5) that occurred in the capital area from January 15th to 18th showed that the contribution rate from abroad starting from 57% gradually decreased due to atmospheric congestion.

The National Institute of Environmental Research analyzed and announced the causes of the high concentration of fine dust in the metropolitan area from January 15th to 18th, when emergency fine dust reduction measures were taken.

According to the research analyzing the data from fine dust observatories, the contribution rate from outside of the country gradually decreased from 57% on 15th, 45% on 16th, and 38% on 17th ~ 18th.

The Institute reported that after the influx of fine dust in the afternoon of January 15th, secondary dust generation became active due to the emission of domestic fine dust-causing substances along with air congestion and high humidity from January 16th to 18th. And the high concentration of fine dust persisted until it was resolved by the northwesterly wind that started from afternoon of the 18th.

The secondary generation of fine dust refers to the process where the sulfur oxides (SOx) and nitrogen oxides (NOx) in the atmosphere undergo physical and chemical reactions and are converted into fine dusts (sulfate (SO₄₂-) and nitrate (NO₃-).

The National Institute of Environmental Research concluded that the high density of fine dust occurred because nitrogen oxides released domestically (from vehicles and plants) were accumulated on the ground and converted into nitrate, which is fine dust due to the secondary generation.

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