The characteristics of PM1.0 for aircraft measurement case study using ToF-AMS for pre-campaign KORUS-AQ

Abstract:

Jinsoo Choi, Jinsoo Park, Joonyoung Ahn, Sangdeok Lee, Hyunjae Kim, Jun Oh, Youdeog Hong, Jihyung Hong, TaeHyeng Lee¹

Air Quality Division, National Institute of Environmental Research, Korea

¹Department of Environmental Science, Hankuk University of Foreign Studies, Korea

For the Pre-KORUS-AQ Campaign during the period from May 18 to June 13 2015, aircraft observations were conducted: four times over the Yellow Sea and three times above Seoul Metropolitan Area (SMA).

Aerosol (PM_1.0) chemical composition and particles size distribution from 50 to 1000 nm were measured and analyzed using ToF-AMS installed the airplane (Kingair-C90GT, USA) in semi-real time. Concentrations of CO and the number of particles were measured as well.

To analyze the aerosol’s spatial and vertical characteristics, 5 flight paths were designed and the main paths were a cross over above SMA and spatial and vertical profile paths over the Yellow Sea. The flight distance varied from 600 to 900km and the velocity was kept at around 200 to 250 km/hr.

On June 13 2015, the sky in SMA was densely fogged and the PM concentrations were relatively higher than usual. As for concentrations of main fine particles, Sulfate was 6.1 mg/m³, Organic 20.7 mg/m³, Ammonium 2.9 mg/m³ and Nitrate 2.9 mg/m³. Group of organic components consisted of 38.3% C_xH_y, 30.4% C_xH_yO₁, 27.4% C_xH_yO₂, 2.9% C_xH_yN_p and 1.0% C_xH_yO_zN_p, and the proportion of oxidation group was 57.9%. As for C_xH_yO₁ and C_xH_yO₂ groups that are generated from decomposition process of oxidized organic compounds and closely related to SOA, the concentrations were 1.5 times higher than C_xH_y group’s that is related with POA; it is considered that the high concentration on the 13th was highly affected by SOA.

In the morning of the same day, aircraft measurements were conducted at the altitude between 600 and 2,700m above the Yellow Sea level, which revealed measurements of Sulfate 4.8 mg/m³, Organic 35.8 mg/m³, Ammonium 3.0 mg/m³ and Nitrate 3.7 mg/m³; these are similar to or higher than the SMA levels. Ionic group of organic components was composed of 43.4% C_xH_y, 30.1% C_xH_yO₁, 23.8% C_xH_yO₂, 1.9% C_xH_yN_p and 0.8% C_xH_yO_zN_p, and the proportion of oxidized group was about 1.2 times higher than CxHy group; which was similar to the composition of the organic components in SMA.