Chemical Composition Characteristics of Particulate Matter in Seoul Metropolitan Area during the Pre-campaign Period of KORUS-AQ

Abstract:

While the current concentration of particulate matter (PM₁₀) in the metropolitan areas of South Korea shows a continuous decreasing tendency, the high concentration episodes have reportedly been increasing. The Ministry of Environment of Korea plans to promote the Korea-US Air Quality Campaign (hereinafter referred to as KORUS-AQ) in cooperation with NASA, to identify the drivers of particulate matter and ozone and improve the accuracy of forecasting models.

The purpose of this research is to identify the chemical composition characteristics of particulate matters (PM₁₀ and PM_2.5) by analyzing the filters collected at the Seoul intensive monitoring site during the pre-campaign period. From May 18 through June 19 in 2015, we collected the PM₁₀ and PM_2.5 samples from 10 am to 9 am the next day every day for 23 hours by using the low-volume air sampler at KIST, located in Hawolgok-dong, Seongbuk-gu, Seoul, Korea, to analyse fine dust concentration and ionic, carbonaceous, and elemental components.

During the research period, the PM₁₀ and PM_2.5 mass concentrations were within 21.1 - 78.5 ug/m³ and 12.0 - 56.0 ug/m³, respectively and the average PM₁₀ and PM_2.5 mass concentrations were 42.5 ug/m³ and 24.6 ug/m³, respectively. In 24.6 ug/m³ of the average PM_2.5 mass concentration, anions were 37.1 %( 9.7 ug/m³) and cations were 13.9%( 3.6 ug/m³), indicating that 51% of the PM2.5 components were ions. In the ionic components of PM_2.5, sulfate showed the highest concentration (7.03 ug/m³), followed by nitrate (2.61 ug/m³), chloride (0.08 ug/m³), ammonium (3.14 mu/m³), sodium (0.17 ug/m³), kalium (0.15 ug/m³), calcium (0.11 ug/m³), and magnesium (0.01 ug/m³).

The average concentrations of carbonaceous components of PM_2.5 were 4.2 ug/m³ (18.7 %) for organic carbon (OC) and 2.2 ug /m3 (9.8 %) for inorganic carbon (EC), indicating that PM_2.5 had total 6.4 ug/m³ (28.5 %) of carbon. As a result of the analysis on elemental components, it was shown that PM_2.5 had 1.61 ug/m³(6.9 %) of crustal materials and 0.08 ug/m³ (0.4 %) of trace metals that accounted for 7.3%. PM₁₀ was high in crustal materials, as it had 7.40 ug/m³(18.0 %) of crustal materials and 0.15 ug/m³ (0.4 %) of trace metals that accounted for 18.4%. Compared to PM_2.5, PM₁₀ showed high concentrations of K, Ca, Ti, Fe, and Zn that are the main components of fugitive dusts and crust materials.