Characteristics, evolution, and sources of OC and EC fractions with insights into secondary organic aerosol formation at a traffic site in Istanbul
Atmospheric Pollution Research, cilt.17, sa.8, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 17 Sayı: 8
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.apr.2026.103074
- Dergi Adı: Atmospheric Pollution Research
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, INSPEC
- Anahtar Kelimeler: Carbonaceous aerosols, OC-EC fractions, Secondary organic carbon, Source apportionment, Urban air pollution
- Marmara Üniversitesi Adresli: Evet
Özet
Concentrations of organic carbon (OC1–OC4) and elemental carbon (EC1–EC6) fractions were investigated to characterize their distributions, temporal evolution, and possible sources at an urban traffic site in Istanbul. PM2.5 samples were collected during six intensive sampling campaigns between January 2017-January 2018, with six daily 2 h daytime samples and one 12 h nighttime sample. Thermal-optical analysis was performed using the NIOSH870 protocol, in which OC fractions were evolved at 310, 475, 615, and 870 °C, and EC fractions at 550, 625, 700, 775, 850, and 870 °C. The annual total carbon concentration was 15.4 ± 5.8 μg m−3, with OC1 (30%) and EC3 (18.8%) as the dominant fractions, while EC1, EC5, EC6, and pyrolyzed carbon exhibited concentrations below 0.5 μg m−3 accounting for less than 0.8%. Most OC1–OC4 were higher during the daytime, whereas EC1–EC3 showed stronger nighttime contributions, indicating distinct diurnal influences of traffic emissions, residential heating, and atmospheric dispersion. Estimated primary and secondary organic carbon (POC, SOC) were generally higher during the daytime and nighttime, respectively. The wintertime and nighttime enhancement of SOC was consistent with lower temperatures, high relative humidity, shallow boundary layers, and weak atmospheric dispersion. Thermal-fraction patterns, interpreted with support from previous studies and principal component analysis, suggested mixed influences from traffic emissions and residential heating, while polar plots and trajectory cluster analysis indicated that POC was more strongly associated with regional transport under higher wind-speed conditions, whereas SOC was linked mainly to local formation and accumulation under low-wind, weak-dispersion conditions.