Title Page
Contents
Abstract 15
Abstract (Korean) 19
Chapter Ⅰ. Physicochemical and temporal characteristics of individual atmospheric aerosol particles in urban Seoul during KORUS-AQ Campaign: Insights from single-particle analysis 22
1. Introduction 22
2. Experimental section 25
2.1. Sampling 25
2.2. Determination of individual particle types by low-Z particle EPMA 27
3. Results and discussion 28
3.1. Characteristics and abundances of individual particle types 28
3.2. Temporal chemical composition variations of individual aerosol particles during the KORUS-AQ campaign 45
4. Conclusions 58
References 60
Supporting materials 73
Chapter Ⅱ. Temporal variations of airborne microplastic particles in ambient PM10 aerosols: Novel analytical approach 75
1. Introduction 75
2. Experimental section 79
2.1. Sampling 79
2.2. Sample treatments 81
2.3. Materials 85
2.4. Fluorescence microscopy, SEM/EDX, RMS, and their off-line combined use 85
3. Results and discussion 88
3.1. A systematic investigation for analyzing AMP particles in an ambient PM10 aerosol sample. 88
3.2. Temporal variations of AMP particles in ambient PM10 aerosols 108
4. Conclusions 115
References 117
Supporting materials 126
Chapter Ⅲ. Direct observation of particle-to-particle variability of ambient aerosol pH: An innovative analytical approach 133
1. Introduction 133
2. Experimental section 137
2.1. Materials 137
2.2. Preparation of SERS-active Ag-MPY-pH substrate 138
2.3. Measurements 139
2.4. Ambient aerosol sampling 139
3. Results and discussion 141
3.1. Novel analytical technique for single-particle pH determination 141
3.2. pH of individual ambient aerosol particles 145
4. Conclusions 155
References 156
Supporting materials 167
Publications 173
Presentations 174
Table 1-1. Characteristic morphologies and chemical compositions and possible sources of individual particle types. 29
Table 1-2. Relative abundances of genuine and reacted mineral dust and SSA particles. 35
Table 2-1. Relative abundances of individual particle types for aerosol sample sections 1-3. 93
Table 2-S1. Count and proportion of stained and AMP particles/m³ across eight samples. 130
Figure 1-1. Map of the sampling site. 26
Figure 1-2. Morphology, X-ray spectra, and elemental compositions of (a) SOA, (b) SOIA (high inorganic), (c) SOIA (high organic), (d) reacted aluminosilicate, and (e)... 32
Figure 1-3. Morphology, X-ray spectra, and elemental compositions of (a) aged soot aggregates, (b) tar balls, (c) char, (d) fly ash, (e) and (f) Zn-HMs, and (g) Mn/Ti-HMs. 39
Figure 1-4. Heavy metals observed in HMs for (a) PM₂.₅₋₁₀ and (b) PM₁₋₂.₅ fractions. 42
Figure 1-5. Morphology, X-ray spectra, and elemental compositions of biogenic particles: (a) fungal spore, (b) microorganism, and (c) trichome or leaf fragments. 44
Figure 1-6. Relative abundances of various particle types in the PM₂.₅₋₁₀ and PM₁₋₂.₅ fractions. 46
Figure 1-7. Typical secondary electron images of PM₁₋₂.₅ aerosol particles collected on (a) 5/23 PM and (b) 5/25 AM. (RM : reacted mineral dust) 49
Figure 1-8. Relative abundances of secondary aerosols, reacted mineral dust, and reacted SSA particles during the KORUS-AQ campaign. 50
Figure 1-9. Relative abundances of combustion particles and heavy metal-containing particles during the KORUS-AQ campaign. 51
Figure 2-1. Photos of the sampling site. The red triangle indicates the sampling place. 80
Figure 2-2. Fluorescence images of representative plastic particles (PS, PE, PP, PET, PVC, PES, and nylon), mineral dust (feldspar, kaolinite, and quartz), carbon black,... 83
Figure 2-3. Fluorescence images of representative biogenic species, including pollen, petal, leaf, and stem, before and after the digestion treatment. 84
Figure 2-4. (a) Fluorescence image, (b) optical image, (c) overlapped image of fluorescence and optical images, and (d) SEM image obtained from the same field... 87
Figure 2-5. Schematic diagram of the sample treatments and analytical methods applied to each sample section. 89
Figure 2-6. X-ray spectra and morphology of typical particles; (a) mineral dust, (b) secondary aerosol particles (AS: ammonium sulfate, SOA: secondary organic... 91
Figure 2-7. Morphology (fluorescence, optical, and SE images), X-ray spectra, and Raman spectra of four representative microplastic particles: (a) PS, (b) PE, (c) ABS,... 96
Figure 2-8. Morphology of PS, PE, ABS, and PET AMP particles 98
Figure 2-9. Morphology and X-ray spectra of typical stained mineral dust (a, b) and carbon-rich (c, d) particles 100
Figure 2-10. (a) Fluorescence image, (b) optical image, (c) overlapped image of the fluorescence and optical images, and (d) SEI for tire/road wear particles (generated... 102
Figure 2-11. (a) Fluorescence image, (b) optical image, (c) overlapped image of the fluorescence and optical images, and (d) SEI for tire-tread particles on the same field... 104
Figure 2-12. Size distribution of AMP and tire/road wear particles in ambient PM10 aerosols. 107
Figure 2-13. Temporal variations of AMP particles during the sampling period. 110
Figure 2-14. Number concentration of AMP particles relative to PM concentration during sampling period. 112
Figure 2-15. Relative abundance of the seven AMP species during the sampling period. 114
Figure 3-1. Schematic diagram of the measurement setup: (a) a sample cell, (b) hygroscopicity setup, and (c) Raman microspectrometry 140
Figure 3-2. (a) Schematic diagram for measurement of individual aerosol pH using SERS. (b) Representative SERS spectra from nebulized aerosol particles using... 142
Figure 3-3. Comprehensive view of representative individual ambient PM10 aerosol particles: (a) optical images at varying RHs, (b) SERS spectra, and (c) secondary... 146
Figure 3-4. Chemical composition-dependent particle-particle variability in pH of 11 individual particles aligned with the calibration curve. 151
Figure 1-S1. Hourly values of PM10 and PM2.5 concentrations recorded in Olympic Park, Seoul, during 5/23-6/5, 2016. The blue dots are the sampling times... 73
Figure 1-S2. Typical 72-h backward trajectories at 3 different receptor heights (250, 500, and 1000 m above ground level) for (a) 5/23, (b) 5/25, (c) 5/29, (d) 5/30, (e)... 74
Figure 2-S1. Raman spectra of standard plastics and AMPs. 128
Figure 2-S2. Hourly values of PM10 and PM2.5 concentrations recorded at a nearby sampling site during 8/8-8/20, 2023. The blue boxes are the sampling dates. 129
Figure 2-S3. Representative Raman spectra of seven AMP species observed in this study. 131
Figure 2-S4. 24-h backward airmass trajectories at 250 m receptor heights. (a) 230809, (b) 230813, (c) 230814, (d) 230815, (e) 230816, (f) 230817, (g) 230818,... 132
Figure 3-S1. Surface morphology of Ag-MPY-pH substrate at different magnifications: (a) x10,000 and (b) x50,000. (c) 3-D SERS plots showing peak... 167
Figure 3-S2. Reproducibility of Ag-MPY-pH substrates examined for five batches by nebulizing standard ammonium sulfate solution. The dashed curve... 169
Figure 3-S3. Temporal stability of Ag-MPY-pH substrate based on nebulized aerosol particles from standard solutions. The dashed curve represents the pH... 170
Figure 3-S4. Normalized X-ray spectra demonstrating the subtraction method. 'Particle 1' shows the original spectral data, while 'Subtracted' illustrates the... 171
Figure 3-S5. Comprehensive view of seven individual ambient PM10 aerosol particles: (a) optical and SE images, (b) SERS spectra, and (c) X-ray spectra.... 172