Contribution of Physical and Chemical Properties to Dithiothreitol-Measured Oxidative Potentials of Atmospheric Aerosol Particles at Urban and Rural Sites in Japan

Dithiothreitol-measured oxidative potential (OP^DTT) can chemically quantify the adverse health effects of atmospheric aerosols. Some chemical species are characterized with DTT activities, and the particle diameter and surface area control DTT oxidizability; however, the physical contribution to OP^DTT by atmospheric aerosols is controversial. Therefore, we performed field observations and aerosol sampling at urban and rural sites in Japan to investigate the effect of both physical and chemical properties on the variation in OP^DTT of atmospheric aerosols. The shifting degree of the representative diameter to the ultrafine range (i.e., the predominance degree of ultrafine parti-cles) was retrieved from the ratio between the lung-deposited surface area and mass concentrations. The chemical components and OP^DTT were also elucidated. We discerned strong positive correlations of K, Mn, Pb, NH4⁺, SO4²⁻, and pyrolyzable organic carbon with OP^DTT. Hence, anthropogenic combustion, the iron–steel industry, and secondary organic aerosols were the major emission sources governing OP^DTT variations. The increased specific surface area did not lead to the increase in the OP^DTT of atmospheric aerosols, despite the existing relevance of the surface area of water-insoluble particles to DTT oxidizability. Overall, the OP^DTT of atmospheric aerosols can be estimated by the mass of chemical components related to OP^DTT variation, owing to numerous factors control-ling DTT oxidizability (e.g., strong contribution of water-soluble particles). Our findings can be used to estimate OP^DTT via several physicochemical parameters without its direct measurement.