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3.3 Influences of Chemical Components on OSIA and exhaust (V, Ni) and secondary organic aerosols (Fig. 2a). Southerly winds tend to prevail during the summer, resulting in influences from sources in industrial areas of the coastal bay south of the measurement site (Fujitani, et al., 2021). The OSIA and OP per unit air volume and per unit PM mass (Fig. 2d) for both extracted samples were mostly highest in October 2015. In the next section, the relationship between OSIA or OP and the chemical components is discussed. Fig. 2 a) Concentrations and fractions of chemical compositions during each observation period at the Tsukuba sampling site, b) Numbers of open burning events for different month, obtained through annual observations in 2016 in Tsukuba (Tomiyama, et al., 2017), and boxplots for each observation period; c) Chemical components exhibiting OSIA or OP, d) Oxidative stress induction ability (OSIA) and oxidative potential (OP) expressed in per unit air volume and in per unit PM mass. Error bars in a) represent the standard deviation of the data during the sampling period. The horizontal bar in the boxes represents the median value. The upper and lower bounds of the boxes represent the 25th and 75th percentiles, with whiskers extending to the highest and lowest data values. POA in a-2) indicates primary emitted OA other than HOA and BBOA. Oxidative Stress Induction Ability of Particles Emitting from Agricultural Open Burning in Japan OP Figure 3 shows OSIA and OP values, the contribution fraction of each component to OSIA and OP, and compositional fraction of each chemical component exhibiting OSIA or OP for each sample in October 2015 and the average values of each season. The fraction of each component to OSIA or OP was determined by the concentrations of the chemical species responsible for OSIA or OP and their unit values of OSIA [fold change μg-component-1] or OP [nmol-DTT min-1 μg-component -1], the values of which were obtained by Fujitani et al. (2023). The OSIA of each component was summed assuming that a linear relationship was valid to obtain the total OSIA of all components, and the fraction of each component to the total OSIA was determined. The fraction of each component to the total OP was obtained by the same procedure. Water-soluble metals and PMF-organic aerosol were considered to exhibit OSIA or OP in the calculations for the water-soluble samples, while PMF-organic aerosol and elemental carbon were considered for the water-insoluble samples. Furthermore, among the metals, Mn, Fe, Ni and Cu, which showed OP in reagent solution experiments, were considered, and for showing OSIA, Zn, Pb, V and Cr were considered in addition to the OP-exhibiting metals. For each metal component, components was calculated using the measured total concentration and the average water-soluble fraction obtained from the summer and winter samples. Metals and elemental carbon derived from vehicle tailpipe emissions and BB emissions were calculated assuming an emission source profile, using those used in the Chemical Mass Balance model (Takahashi et al., 2011) and the concentration the of water-soluble 31

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