Fine Dust from China + Korean Vehicle Emissions = 'High-Concentration Ultrafine Dust in the Seoul Metropolitan Area'

The city center viewed from Namsan in Seoul on the 12th, when the fine dust concentration was at the 'Bad' level, is shrouded in fine dust. Photo by Jinhyung Kang aymsdream@

[Asia Economy Reporter Junho Hwang] The reason for the unusually high concentration of ultrafine dust in the Seoul metropolitan area has been revealed. A study has found that fine dust originating from China combines with domestically generated fine dust, such as automobile exhaust, and through chemical reactions, increases the concentration of ultrafine dust. It is anticipated that reducing nitrogen oxide emissions could lower the concentration of ultrafine dust.

Dr. Jinyoung Kim's research team at the Environmental Welfare Research Center of the Korea Institute of Science and Technology recently published these findings in the international atmospheric science journal Atmospheric Chemistry and Physics, announced on the 27th.

Moist Chinese Fine Dust Meets Domestic Exhaust, Expanding Ultrafine Dust

This is a schematic diagram illustrating the process of high-concentration fine dust occurrence in the Seoul metropolitan area due to the combined enhancement effect of long-range inflow of foreign fine dust under domestic stagnant atmospheric conditions and the accumulation of domestic precursor emissions.

The research team uncovered why the concentration of ultrafine dust in the Seoul metropolitan area is higher than the fine dust concentration in China. High concentrations of ultrafine dust occur in the Seoul metropolitan area during winter and spring, and the team identified the cause by analyzing the thermodynamic properties of fine dust.

The team analyzed ultrafine dust (PM2.5) concentrations by measurement date under conditions categorized as 'overseas inflow,' 'domestic atmospheric stagnation,' and 'overseas inflow + domestic atmospheric stagnation.'

As a result, under atmospheric stagnation conditions without overseas fine dust inflow, the ultrafine dust concentration was 34 μg/m³. When Chinese fine dust inflow occurred, it rose to 53 μg/m³. When domestic atmospheric stagnation was also present, the concentration reached the highest level at 72 μg/m³. Additionally, in cases with Chinese fine dust inflow, secondary pollutants such as sulfate, nitrate, and ammonium within the ultrafine dust, as well as moisture content, were found to be richer compared to cases without such inflow.

Sulfates and nitrates have a strong ability to absorb moisture, thereby increasing the water content within particles. Moist fine dust entering the metropolitan area comes into contact with nitrogen oxides emitted from automobile exhaust and other sources. This contact further generates nitrates within the particles. The repeated combination of nitrates and moisture causes the fine dust concentration to continuously increase.

Ultrafine dust consists of particulate matter with an aerodynamic diameter of 2.5 μm or less. It appears as a mixture of solid or liquid particles composed of carbon components (organic carbon, elemental carbon) and inorganic ion components (sulfate, nitrate, ammonium).

Reducing Exhaust Emissions is Essential for Survival

This is the result of analyzing the relationship (right) between nitrogen dioxide (NO2) concentration and PM2.5 nitrate (NO3-) component in the atmosphere under domestic stagnation (S) and ventilation (V), and foreign long-range fine dust inflow (T) and no inflow (nT) conditions.

The research team expects that reducing nitrogen oxides in Korea will decrease the occurrence of high concentrations of ultrafine dust.

To prevent nitrogen oxides from reacting with moisture in fine dust and converting into nitrates, either atmospheric ammonia or nitrogen oxides must be reduced. However, reducing ammonia could acidify ultrafine dust particles during the process, potentially increasing health risks. Therefore, the research team anticipates that policies aimed at reducing exhaust emissions to lower nitrate components in the atmosphere will be the most effective solution.

Dr. Jinyoung Kim stated, "Through this study, we were able to specifically reveal the complex mechanism by which fine dust from China, combined with nitrogen oxides emitted from domestic automobiles and industrial facilities, increases ultrafine dust concentrations in the metropolitan area. We hope this research will serve as a foundation for more effective ultrafine dust management policies in the Seoul metropolitan area in the future."

This content was produced with the assistance of AI translation services.