Estimation of PM2.5 Emission Sources in the Tokyo Metropolitan Area by Simultaneous Measurements of Particle Elements and Oxidative Ratio in Air

• Published in: ACS earth and space chemistry Vol. 4; no. 2; pp. 297 - 304
• Main Authors: Kaneyasu, Naoki, Ishidoya, Shigeyuki, Terao, Yukio, Mizuno, Yusuke, Sugawara, Hirofumi
• Format: Journal Article
• Language: English
• Published: American Chemical Society 20.02.2020
• Subjects: emission source estimation; OR; elemental ratio; PM2.5; CO2; oxidative ratio; aerosol
• ISSN: 2472-3452; 2472-3452
• DOI: 10.1021/acsearthspacechem.9b00314

Researchers across research domains have traditionally used two different methods to characterize the emission sources of pollution in the atmosphere. One of the widely used methods in the area of air pollution utilizes the ratio of elements in aerosol, namely, PM2.5. The other method used in climate-related research is the oxidative ratio (OR = −ΔO2/ΔCO2) in air. In this study, these two methods were simultaneously applied for the first time to estimate the source of PM2.5 pollution. During a week-long pollution event that occurred in the Tokyo Metropolitan area, Japan, two concentration maxima were observed in the temporal plot of PM2.5. The slope of the linear regression line for the Pb versus Ni concentration plot during the first PM2.5 concentration maximum was approximately 4 times larger than that of the second, indicating that the former was dominated by Pb-rich emission sources, that is, coal combustion. The ORs in air measured during the corresponding concentration maxima were 1.33 and 1.51, suggesting the prevailing contributions of CO2 emitted from coal and oil combustions, respectively. This suggests that the results from elemental ratio and OR analyses were consistent in identifying the emissions from these important fuel types. The results obtained in our study demonstrated that OR in the air is also applicable to estimate the emission sources of PM2.5, providing more information on the phase of the combusted materials, that is, gaseous, liquid, or solid phase. Such a study should improve the estimation of emission sources both in air pollution and climate-related research.