제주시 도심지역 대기 중 미세먼지의 조성 특성과 오염원 추정

Abstract

Particulate matter (PM) are the complicated mixtures of the chemical materials which are directly emitted from the natural and anthropogenic sources or formed as the secondary pollutants from the primary emissions through chemical reactions. Thus, the chemical composition of PM provides useful data for evaluating the sources of PM. In order to manage the air quality in the local area, it is essential to understand the chemical composition and source of PM. This study was conducted to understand characteristics of chemical compositions and estimate sources affecting PM, especially in the local living environment of Jeju City where is getting more urbanized. The mass concentration and chemical composition of PM were investigated at the Jeju City. PM2.5 samples were collected intensively from 2017 to 2018 at Yeongdong air pollution monitoring site in Jeju City, Korea. Since the source and chemical composition of PM are different depending on size of particles, PM2.5 and PM10 must be investigated simultaneously in order to effectively manage PM. Therefore, PM2.5 and PM10 samples were collected simultaneously in January, April, August, and November 2018 and the concentration of various species contained in PM was analyzed: 9 watersoluble inorganic ions, OC (organic carbon), EC (elemental carbon), and 22 elements. The average mass concentration of PM2.5 was 16.61±9.38 ㎍/㎥ for two years, which is slightly higher than the National Annual Average Standard (15 ㎍/㎥) for PM2.5. The PM2.5 level became relatively higher when the northwest wind blew. The average mass concentration of PM10 was 33.42±21.15 ㎍/㎥, and the PM2.5/PM10 ratio was 0.47 in 2018. PM consisted mainly of ionic species, carbon species, and elements. Ions, carbon and elements contributed 56.7%, 18.0%, and 7.0% to PM2.5 mass, respectively and 45.4%, 11.0% and 13.8% to PM10 mass, respectively. Secondary ions (SO4 2-, NO3- , NH4+) were the most abundant species in PM2.5, accounting for 52.2% of PM2.5 mass. In PM2.5, about two-thirds of total carbon were occupied by OC and the ratio of OC/EC was 4.23. The elements contained in both PM2.5 and PM10 were mostly soil and sea salt origin components. The chemical composition of PM showed that the contribution of secondary aerosol ions and carbon species in PM2.5 and that of natural origins such as soil and sea salt in PM10 were significant. The component materials that constitute PM2.5 and PM10 were investigated using mass reconstruction methods. AMSUL (ammonium sulfate) in PM2.5 and CM (crustal materials) in PM10 showed the largest component ratio. When the PM2.5 showed high concentration, the concentrations of secondary aerosols such as AMSUL and AMNIT (ammonium nitrate) also showed a distinct increase. The concentration of CM, in particular, increased significantly when PM10 showed high concentration. It can be found from the concentration ratio of NO3-/SO4 2- that the PM in the downtown area of Jeju City was more affected by mobile sources compared with that in the background area of Jeju Island. According to the enrichment factor, Cl- and Mg2+ were found to be originated from sea salt, while Al, Ti, Ca, Sr, and Fe were highly likely to be crustal/soil origins. From the results of the PMF analysis, it was found that nine types of sources, named secondary sulfate, secondary nitrate, oil combustion, biomass burning, vehicle, coal combustion, soil, sea salt, and industry, were affected on the chemical composition of PM. Among these possible sources, the contribution of secondary sulfate was the largest at 28.9% in PM2.5 and the soil source contribution was the highest at 30.5% in PM10. Compared with the possible sources in the other cities in Korea, the contribution of secondaryaerosol was found to be greater than that of sources for the combustion and vehicle in Jeju City where there is little impact from primary emissions. The major component and the dominant sources under the high PM episodes were tried to be identified, based on data for chemical composition of PM. Secondary ionic species (SO4 2-, NO3- , NH4+) and organic matter in PM2.5 were important contributors to the occurrence of the high concentration of PM2.5, while CM was a substance that contributed greatly to the high concentration of PM10 during the period of Asian Dust. When episode with high concentration of PM2.5 occurred in Jeju City, the effects of secondary aerosol sources were predominant. By specifying the cases of pollution phenomena with the high concentration of specific chemical species along with the high concentration of PM, the sources of PM that could not be estimated using PMF analysis could be identified. Despite the absence of distinct sources that affect the local air quality in Jeju City, the high PM episodes are observed every year and various types of sources are also being identified in this study. Based on the results of this study, long-term and consistent observation and multidisciplinary research should be carried out in order to clearly interpret the pollution characteristics of PM that affect the local air quality of Jeju City