Asian Journal of Atmospheric Environment Vol. 7-3, pp.139-151, September 2013 doi: http://dx.doi.org/10.5572/ajae.2013.7.3.139 Airborne Measurements of Ozone and Its Precursors over Yeosu-Gwangyang Industrial Areas in the Southern Coast of Korea So-young Kim*, Seok-jun Seo, Hyun-ju Park, Jung-seok Son, Ji- hoon Park and Jong-choon Kim Air Quality Research Division, National Institute of Environmental Research Kyungseo-dong, Seo-gu, Incheon 404-708, Korea *Corresponding author. Tel: +82-32-560-7276, E-mail: [email protected] absorbing 95% to 99% of the sun’s harmful ultraviolet ABSTRACT rays. The recently increasing levels of ozone in the troposphere, however, have been known to not only The purpose of this study is to understand distributio- affect human health by irritating the eyes and respira- nal characteristics in the atmospheric concentra- tory system, but also do harm to crops (Papayannis et tions of O and its precursors based on data taken 3 al., 1998; Herman et al., 1996). Tropospheric ozone at the southern Korean coast. The average O con- 3 is mainly formed from the reaction of volatile organic centration in the high altitude was found to range from 32.3 to 90.8 ppb with a maximum concentra- compounds (VOCs) and nitrogen oxides (NOx) under strong sunlight with almost no wind (Chameides et tion of 132 ppb. The ambient O3 concentration was high at altitudes of 1000 m and 500 m above the sou- al., 1992; Fehsenfeld et al., 1992). In urban areas, thern sea near Gwangyang Bay and an industrial area where many sources of NOx and VOCs exist, the containing emission sources. The daily mean concen- amount of ozone generation fluctuates widely due to photochemical reactions, transportation, and accumu- trations of NOy and CO were 6.7-24.2 ppb and 0.152- 0.487 ppm, respectively. During the aerial measure- lation (Wang et al., 2001; Kleinman et al., 2000). Gwangyang Bay, the site for this study, has an east- ment period, the highest mean concentration of O3 was observed on June 1. The aerial measurement west length of 27 km and a north-south length of 15 results showed that the maximum ozone concen- km. It is surrounded by areas such as Gwangyang, tration was observed to be 132 ppb in the high alti- Suncheon, Yeosu, Namhae, and Hadong. About 2.9 tude the southernmost part of Yeosu. The measure- billion tons of fresh water flows to this narrow back ment of vertical wind fields in the air indicated that bay from the Seomjin River every year. Gwangyang O3 formed in the southernmost part of Yeosu was Bay is also a major industrial hub where large opera- transported by strong southwesterly winds to the tions, including power plants, petrochemical com- northeast of Gwangyang Bay. This led to a ground plexes, and steel mills, are concentrated. In coastal O3 concentration of over 100 ppb in Jinju, the north- areas such as Gwangyang Bay, the circulation bet- eastern part of Gwangyang Bay. On August 9, when ween land and sea breeze typically affects ozone, and the maximum O3 concentration was 50 ppb, the mea- the wind direction is related to ozone accumulation surement results showed that O3 concentrations were (Cheng, 2002; Liu et al., 1992). This leads to fre- relatively low compared to other days. In particular, quent instances in which air quality standards are ex- low NO2 and TVOC concentrations were observed, ceeded, despite proper awareness and control of air both of which serve to form O3 in photochemical pollution. reactions. Data on ozone warning in Gwangyang Bay during a six-year period from 2003 to 2008 were compared Key words: O3, NO2, TVOC, Gwangyang Bay, Pho- tochemical reactions, Wind with data from metropolitan areas including Seoul, Incheon, and Gyeonggi. It was found that Gwangyang Bay issued ozone warnings more frequently than those metropolitan cities inhabited by more than 20 1. INTRODUCTION million people. Yeosu, Suncheon and Gwangyang issued ozone warnings five times in 2006 and 22 Ozone in the stratosphere serves as a protective times in 2007. This indicates that photochemical shield for plants, animals, and humans on earth by pollution in these areas was significantly higher than 140 Asian Journal of Atmospheric Environment, Vol. 7(3), 139-151, 2013 in other parts of Korea. 60 The high-ozone episodes in the Gwangyang Bay area were usually observed in summer. Many studies into the causes of highly-concentrated ozone have 50 been performed in Korea and abroad. According to a ) � study conducted by the National Institute of Environ- mental Research (NIER) in 2006 to identify the gene- 40 ration of photochemical air pollutants, the main fac- Latitude ( China tors influencing ozone occurrence include temperature, Korea Japan 30 solar radiation, cloudiness, and wind speed. It was found that in similar weather, higher concentrations of NOx and VOCs create more favorable conditions for highly-concentrated ozone. In addition, a study 90 100 110 120 130 140 conducted in Busan, a coastal area like Gwangyang Longitude (�) Bay, showed that higher ozone concentrations and more frequent high-ozone episodes were observed -290 during the early afternoon when sea breeze are usually absent (Oh et al., 2004). The occurrence of ozone is -300 not limited to the surface. The vertical transportation -310 of ozone transferred from neighboring areas or produc- -320 ed from mixed layers is known to have a significant -330 influence as well. Thus, the characteristics of its verti- cal distribution and advection have also been studied -340 (Lee et al., 2009; Helmig et al., 2002). In Korea, -350 many studies on Gwangyang Bay ozone (Ha et al., -360 2006) have focused on ground monitoring results, -370 while almost no measurements have been made using 110 120 130 140 150 160 170 180 190 aircraft in the larger area including Gwangyang Bay Fig. 1. Air quality monitoring stations and meteorological and its background areas. In this study, aircraft mea- observatories around the study site. surement were conducted for the spatial distribution of ozone and its precursors in Gwangyang Bay and neighboring areas to determine the distributional pat- were collected from a network of 14 stations air qua- terns at various latitudes, longitudes, and locations, lity monitoring stations (Fig. 1): four stations in Gwang- and a comparative analysis was made of the spatial yang City (Jeong-dong, Jinsang-myeon, Chilseong-ri, distributions. and Taein-dong), four stations in Yeosu City (Gwang- mu-dong, Munsu-dong, Samil-dong, and Wollae- dong), two stations in Suncheon (Yeonhyang-dong and 2. METHODS Jangcheon-dong), and four stations in Jinju (Daean- dong, Sangbongdong-dong, Sangpyeong-dong, and Various data were used to identify the spatial distri- Ha-dong). To see the air conditionsin each case, wea- bution of ozone and its precursors at the southern ther data were also collected from the nearest meteoro- coast, including the results of aerial observations and logical offices located in Yeosu, Suncheon, Jinju, and ground monitoring and data on ground air and high Tongyeong. For the high altitude, data from the mete- altitude measured during the periods from May 25 to orological office in Gwangju, Jeollanam-do were used. June 15, and July 25 to August 15, 2009. For analysis, data were divided into two groups: 2. 1 Aerial Measurement high concentration days, on which the highest O3 The aircraft used for this study was a Chieftain PA- concentration was observed (100 ppb or higher), and 31-350 twin-engine propeller model (U.S. Piper) low concentration days, on which the highest O3 owned by Changwoon Aviation Co., Ltd. The aircraft concentration was lower than 50 ppb. To analyze the specifications and the measuring method were based aerial measurement results, a comparison was made on Han et al., 2005. between the aerial measurements and ground mea- The inside of the aircraft was equipped with a gas surements, both of which were performed in the same analyzer (a trace-level Thermo model for NOy, O3, time period. The concentration data used for this study and CO) and a Tedlar bag for VOCs. An automatic Airborne Measurements of Ozone and Its Precursors 141 Table 1. Description of relevant instruments equipped on the aircraft. Species Response Technique Range Precision detected time UV Photometric / TEI O ⁄100 ppb 20 sec (10 sec ave.) 1 ppb 3 (Trace Level 49C) Chemiluminescence / TEI NO ⁄100 ppb 60 sec (10 sec ave.) 0.05 ppb y (Trace Level 42C) NDIR / TEI CO ⁄10 ppm 60 sec (10 sec ave.) 0.04 ppm (Trace Level 48C) PAN PMT (GC-Luminol) 30 ppt 3 min - HNO3 Auto sampler / DI water - 5 min 2- SO4 Auto sampler / DI water - 5 min - VOCs GC-FID / Perkin- Elmer --- mass flow control system was installed on the gas analyzer to avoid any alteration to suction flow, which can happen with changes in flight altitude. Table 1 lists the measurement items used in the aircraft above the southern coast. The concentrations of O3, NOy and CO were measured consecutively. Before and after a measurement was performed, corrections to the instrument were made in the laboratory or field based on the installation conditions applied in the aircraft. The instrument was warmed up for two to three hours after beginning its operation. When it was stabilized, the zero gas was released to set background concentration values. An ozone generator made by the Korea Research Institute of Standards and Sci- ence (KRISS) was used to correct the concentration to 7 points or higher in the range of 0-200 ppbv. To measure VOCs, a precursor important to ozone gene- ration, Teflon bags were used to collect samples at several selected points where VOC concentration levels Fig.