Vertical Characteristics of Secondary Aerosols Observed in the Seoul and Busan Metropolitan Areas of Korea during KORUS-AQ and Associations with Meteorological Conditions

Abstract

In this study, the chemical components of aerosols observed at ground level and in upper layers during the Korea–United States Air Quality (KORUS-AQ) campaign were analyzed in two representative metropolitan areas of Korea: the Seoul metropolitan area (SMA) and the Busan-containing southeastern metropolitan area (BMA). First, we characterized emissions using the Clean Air Policy Support System (CAPSS) emission statistics, and compared them with both ground- and aircraft-based measurements obtained during the KORUS-AQ campaign. The emission statistics showed that the SMA had higher NOx levels, whereas BMA had significantly higher SO2 levels. Ground-level observations averaged for the summer season also showed SMA–nitrate and BMA–sulfate relationships, reflecting the CAPSS emission characteristics of both areas. However, organic carbon (OC) was higher in BMA than SMA by a factor of 1.7, despite comparable volatile organic compound (VOC) emissions in the two areas. DC-8 aircraft-based measurements showed that, in most cases, nitrogen-rich localities were found in the SMA, reflecting the emission characteristics of precursors in the two sampling areas, whereas sulfur-rich localities in the BMA were not apparent from either ground-based or aircraft observations. KORUS-AQ measurements were classified according to two synoptic conditions, stagnant (STG) and long-range transport (LRT), and the nitrate-to-sulfate (N/S) ratio in both ground and upper layers was higher in the SMA for both cases. Meanwhile, organic aerosols reflected local emissions characteristics in only the STG case, indicating that this stagnant synoptic condition reflect local aerosol characteristics. The LRT case showed elevated peaks of all species at altitudes of 1.0–3.5 km, indicating the importance of LRT processes for predicting and diagnosing aerosol vertical distributions over Northeast Asia. Other chemical characteristics of aerosols in the two metropolitan areas were also compared.

Statistical Characteristics of Air Quality Index DAQx*-Specific Air Pollutants Differentiated by Types of Air Quality Monitoring Stations: A Case Study of Seoul, Republic of Korea

“…The different sources of O 3 , NO 2 , PM 10 , and PM 2.5 , associated chemical precursors, chemical reactions, and meteorological influences on their concentrations in the ambient air have already been studied in Seoul in many ways [6,14,22,23,25,26,[28][29][30][31][32][36][37][38][39][40]42,[45][46][47]55,[57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74]. Therefore, they can be assumed to be known when discussing their annual cycles.…”

Satellite-Based Diagnosis and Numerical Verification of Ozone Formation Regimes over Nine Megacities in East Asia

“…In East Asia, westerly wind prevails, and the regional O 3 in downwind areas varies by LRT process. Numerous studies have addressed the impacts of the LRT process over the East Asia and Asia-Pacific area [55][56][57][58][59][60][61][62], including the trans-Pacific transport between East Asia and the U.S. [63][64][65][66][67][68][69][70][71]. For this purpose, EXP4-6 were designed to assess the LRT process in East Asia and to estimate how the changes in O 3 in South Korea and Japan are simulated to be accompanied by emission reductions in East China, based on emission reductions (Table 1) by halving the emissions only in East China without changing the emissions in South Korea and Japan.…”