The emissions of several air pollutants (NOx, CO, VOCs, etc.) for the replacement of all diesel buses by Compressed Natural Gas (CNG) buses were estimated in the Busan Metropolitan Area (BMA). These emissions were calculated from emission factors considering the different driving speeds with bus routes, distance traveled, and deterioration factors. For the purpose of this study, three categories of fuel type were selected: (1) the combination of diesel (65%) and CNG buses (35%) (DSL+CNG case), (2) all diesel buses (DSL case), and (3) all CNG buses (CNG case). The emissions of NOx and CO in the CNG case were estimated to be significant decreases (by about 50% and 98%, respectively) relative to the DSL case. Conversely, the emission of VOCs (980.7 ton/year) in the CNG case were a factor of 3.3 higher than that (299.8 ton/year) in the DSL case. In addition, the diurnal variations of emissions between two city buses (e.g. diesel and CNG) and all other vehicles were distinctly different because the two city buses operate at a regular time interval. Our overall results suggest the possibility that the pollutant emissions from the CNG buses can exert less influence on air quality in the target area than those from the diesel buses.

Abstract
 1. 서 론
 2. 자료 및 방법
  2.1. 대상지역
  2.2. 시내버스 배출량 산정방법
  2.3. 격자 배출량 생성방법
 3. 결과 및 고찰
  3.1. 국가 대기오염물질 배출량과의 비교
  3.2. 시내버스 배출 총량 변화
  3.3. 시내버스 배출량 공간분포 변화
  3.4. 시내버스 배출량의 시간별 변화
 4. 결 론
 참 고 문 헌

• 방진희(부산대학교 지구환경시스템학부) | Jin-Hee Bang (Division of Earth Environmental System, Pusan National University)
• 강윤희(부산대학교 지구환경시스템학부) | Yoon-Hee Kang (Division of Earth Environmental System, Pusan National University)
• 송상근(부산대학교 지구환경시스템학부) | Sang-Keun Song (Division of Earth Environmental System, Pusan National University)
• 김유근(부산대학교 지구환경시스템학부) | Yoo-Keun Kim (Division of Earth Environmental System, Pusan National University) Corresponding author