最新の研究成果 Contributions of Biomass Burning to PM_2.5 Level and Oxidative Potential in Suburban Tokyo, Japan

Fine particulate matter (PM_2.5) in the atmosphere is of high priority for air quality management efforts due to well-established associations with adverse effects on human populations. To develop effective countermeasures against PM_2.5 emission sources, its origin needs to be efficiently characterized. In this study, we aimed to estimate source contributions to the PM_2.5 and organic aerosol concentrations with a focus on biomass open burning (e.g., agricultural residues).

Atmospheric PM_2.5 samples were collected once a week from a suburban Tokyo city, Tsukuba, Japan in 2012–2013. The particulate mass, elemental carbon, organic carbon (OC), water-soluble organic carbon, inorganic ionic species, elements, organic markers (compounds), and biological oxidative potentials were measured using the PM_2.5 samples.

The results showed remarkably high levoglucosan concentrations in fall, suggesting enhanced open burning contributions during this season. The analysis of levoglucosan/β-sitosterol ratios suggested that levoglucosan is still a good marker of biomass burning; however, it may be useful to use β-sitosterol in combination with levoglucosan or as a supplement.

Major emission sources and their contributions to the annual average OC concentrations were estimated to be secondary organic aerosols (SOA, 32%), vehicle exhausts (22%), open burning (8.4%), and cooking (5.1%) (Fig. 1). The estimated relative contribution of open burning to OC concentrations was highest in November (20%) and lowest in June (3.3%).

The PM_2.5 oxidative potentials were highest in spring and summer. Correlation and meteorological analyses suggest that emissions from ships (or other residual oil combustion) and anthropogenic SOA originating from the Tokyo Metropolitan Area, and biogenic SOA contribute to an increase in PM_2.5 oxidative potential during the warm season in the suburbs of Tokyo. Neither open burning nor vehicle exhaust source contributions showed a strong positive correlation with the PM_2.5 oxidative potential.

Major sources of organic aerosols were included in the analysis of this study. Future research should aim for a more comprehensive analysis that includes major sources of transition metals, such as tire wear, brake dust, and resuspended road dust, which could potentially drive PM_2.5 oxidative potential.

Fushimi, A., Villalobos, A.M., Takami, A., Tanabe, K., Schauer, J.J. (2024). Contributions of Biomass Burning and Other Sources to Fine Particle Level and Oxidative Potential in Suburban Tokyo, Japan. Aerosol Air Qual. Res., 24, 230291.
https://doi.org/10.4209/aaqr.230291