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열광학적 분석 프로토콜에 의한 유기탄소와 원소탄소 측정값 비교

Comparison of OC and EC Measurement Results Determined by Thermal-optical Analysis Protocols

  • 김효선 (한국표준과학연구원 대기환경표준센터) ;
  • 정진상 (한국표준과학연구원 대기환경표준센터) ;
  • 이진홍 (충남대학교 환경공학과) ;
  • 이상일 (한국표준과학연구원 대기환경표준센터)
  • Kim, Hyosun (Center for Gas analysis, Korea Research Institute of Standards and Science) ;
  • Jung, Jinsang (Center for Gas analysis, Korea Research Institute of Standards and Science) ;
  • Lee, Jinhong (Department of Environmental Engineering, Chungnam National University) ;
  • Lee, Sangil (Center for Gas analysis, Korea Research Institute of Standards and Science)
  • 투고 : 2015.08.27
  • 심사 : 2015.09.30
  • 발행 : 2015.10.31

초록

Carbonaceous aerosol is generally classified into OC (organic carbon) and EC (elemental carbon) by thermal optical analysis. Both NIOSH (National institute of occupational safety and health) with high temperature (HighT) and IMPROVE-A (Interagency monitoring of protected visual environments) with low temperature (LowT) protocols are widely used. In this study, both protocols were applied for ambient $PM_{2.5}$ samples (Daejeon, Korea) in order to underpin differences in OC and EC measurements. An excellent agreement between NIOSH and IMPROVE-A protocol was observed for TC (total carbon). However, significant differences between OC and EC appeared and the differences were larger for EC than OC. The main differences between two protocols are temperature profile and charring correction method. For the same charring correction method, HighT_OC was 10% higher than LowT_ OC, while HighT_EC was 15% and 33% lower than LowT_EC for TOT (thermal-optical transmittance) and TOR (thermal-optical reflectance), respectively. This difference may be caused by the temperature of OC4 in He step and possibly difference in POC (pryorilized OC) formation. For the same temperature profile, OC by TOT was about 26% higher than that by TOR. In contrast, EC by TOT was about 50% lower than that by TOR. POC was also dependent on both temperature profile and the charring correction method, showing much distinctive differences for the charring correction method (i.e., POC by TOT to POC by TOR ratio is about 2). This difference might be caused by different characteristics between transmittance and reflectance for monitoring POC formation within filters. Results from this study showed that OC and EC depends on applied analysis protocol as shown other studies. Because of the nature of the thermal optical analysis, it may not be possible to have an absolute standard analysis protocol that is applicable for any ambient $PM_{2.5}$. Nevertheless, in order to provide consistent measurement results for scientists and policy makers, future studies should focus on developing a harmonized standard analysis protocol that is suitable for a specific air domain and minimizes variations in OC and EC measurement results. In addition, future elaborate studies are required to find and understand the causes of the differences.

키워드

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