대기 중 에어로졸 산성도(pH) 및 수분함량(ALWC) 측정기법 개발을 통한 질산염 생성 이해

다국어 초록 (Multilingual Abstract)

This study developed a real-time aerosol pH measurement system based on a Particle-Into-Liquid Sampler (PILS) to overcome the limited temporal resolution of conventional filter-based methods. By continuously analyzing liquid samples collected in real time, high-resolution aerosol pH could be obtained, and the reliability of the system was verified through comparison with the U.S. EPA-recommended filter extraction method. When applied to a winter urban environment, aerosol acidity was found to persist due to rapid NO3- formation under ammonium-rich conditions, which outpaced neutralization. The production of hydrogen ions accompanying NO3- formation further lowered pH, indicating that NO3- acts as a key driver of acidity in wintertime urban aerosols. Low temperatures and high relative humidity suppressed the volatilization of HNO3 and promoted aqueous-phase reactions, facilitating stable particulate NO3- formation. In contrast to observations, the ISORROPIA II model persistently overestimated pH under high ALWC and exhibited biases in NO3-–HNO3 partitioning, suggesting that it inadequately represents heterogeneous and aqueous-phase processes under winter urban conditions. These discrepancies highlight the influence of ALWC on aerosol acidification and underscore the need for integrated studies of pH and ALWC.
To address this, we developed a real-time ALWC estimation technique using two T640 PM Monitors, defining ALWC as the mass difference between undried and dried aerosols. ALWC sharply increased when relative humidity exceeded 80 % and showed strong dependence on temperature and dry aerosol mass concentration. The real-time PILS-pH and ALWC measurement approaches presented in this study overcome the spatiotemporal limitations of existing methods, and future integrated pH–ALWC observations are expected to improve the understanding of NO3--driven wintertime acidification mechanisms and enhance the accuracy of pH assessments.

목차 (Table of Contents)

• 제1절 서론 1
• 1.에어로졸(PM2.5) 1
• 2.에어로졸 산성도 (pH) 3
• 3.에어로졸 수분 함량 (ALWC) 6
• 4.연구목적 8
• 제2절 실험 방법 10
• 2.1 PILS 를 활용한 실시간 에어로졸 pH 측정 10
• 2.1.1 PILS (Particle-Into-Liquid Sampler) 시스템 10
• 2.1.2 pH 측정 시스템 16
• 2.1.3 PILS-pH 시스템에서의 에어로졸 pH 산출 20
• 2.2 실시간 PILS-pH 측정법 및 EPA IO-4.1 간 비교 실험 22
• 2.2.1 필터 추출법 22
• 2.2.2 필터 추출법에서의 에어로졸 pH 산출 27
• 2.3 실시간 PILS-pH 측정법의 적용 28
• 2.3.1 측정 개요 28
• 2.3.2 High resolution Time of flight Aerosol mass spectrometer (HR-ToF-AMS) 31
• 2.3.3 Particles-Into-Liquid Sampler with Ion Chromatography (PILS-IC) 33
• 2.3.4 Gas Analysis 35
• 2.3.5 Others 38
• 2.3.6 QA/QC 40
• 2.4 열역학적 평형 모델(ISORROPIA II)의 에어로졸 pH 추정 47
• 2.5 T640 PM Monitor 을 활용한 실시간 ALWC 측정 49
• 2.5.1 실제 대기 조건을 고려한 ALWC 측정 환경 조성 49
• 2.5.2 ALWC 측정을 위한 대기 시료의 건조 조건 53
• 2.5.3 Teledyne T640 PM Monitor 55
• 2.5.4 T640 PM Monitor 을 활용한 ALWC 측정 및 계산 방법 57
• 제3절 결과 60
• 3.1 실시간 PILS-pH 측정법의 평가 60
• 3.2 겨울철 도심지역 에어로졸 화학적 특성 64
• 3.3 질산염 생성 기작 72
• 3.4 질산염 생성에 따른 에어로졸 pH 감소 78
• 3.5 RH가 에어로졸 pH 와 질산염 생성에 미치는 영향 84
• 3.6 측정과 열역학 모델(ISORROPIA II)의 비교 87
• 3.6.1 ISORROPIA II 의 예측 편향 87
• 3.6.2 ISORROPIA II 의 질산-질산염 상 분배 93
• 3.6.3 ISORROPIA II 의 에어로졸 pH 예측 편향 원인 분석 95
• 3.7 T640 PM Monitor 를 이용한 실시간 ALWC 측정 98
• 제4절 결론 104
• 참고문헌 107
• Abstract 130
• 감사의 글 133