# Long-Term and Seasonal Changes in Sources of Urban Atmospheric Particulates in the Western Pacific
## 3 Results and Discussion  
### Individual City Trends  
Table S3 shows the fraction of P\({}_{\rm h}\) in the atmospheric P\({}_{\rm c}\) (=\(x\)) and the fraction of P\({}_{\rm c}\) in the atmospheric TSP (=\(y\)) in the 10 cities in the summer and winter from 1997 to 2018, which were calculated by equations of the NP-method using [TSP], [1-NP], and [Pyr] in Table S2. Table 1 shows [P\({}_{\rm c}\)], [P\({}_{\rm h}\)], and [P\({}_{\rm l}\)] in the same samples, which were calculated by using the x and y values in Table S3 and [TSP] in Table S2. In order to know seasonal differences, summer, winter, and annual concentrations of [P\({}_{\rm c}\)] in 10 cities are shown in Table 2 with the winter/summer ratio. In order to compare combustion sources, annual concentrations of [P\({}_{\rm h}\)] and [P\({}_{\rm l}\)] in 10 cities are shown in Table 3 with the [P\({}_{\rm h}\)]/[P\({}_{\rm c}\)] ratio. In these tables, Tokyo was combined with Sagamihara, a suburb of Tokyo. The data in Table 2 shows that the Japanese cities had much lower annual [P\({}_{\rm c}\)] values (less than 2 \(\rm\mu g\) m\({}^{-3}\)) than the cities in the other countries. The [P\({}_{\rm h}\)]/[P\({}_{\rm c}\)] ratios (=\(x\)) of these cities were greater than 0.70, except for Kitakyushu, where the ratio was 0.34. Figure 1 shows the variations of [TSP] and [P\({}_{\rm c}\)] in Kanazawa as typical to those in Japanese commercial cities. [P\({}_{\rm c}\)] was over 10 \(\rm\mu g\) m\({}^{-3}\) in the winter of 1999 with larger [P\({}_{\rm c}\)]/[TSP] ratio (\(y\) = 0.2, Table S3) than those in the other Japanese cities. However, [P\({}_{\rm c}\)] started to decrease in the 2000s, and did not exceed 1 \(\rm\mu g\) m\({}^{-3}\) by the winter of 2018. The seasonal change (summer < winter) in [P\({}_{\rm c}\)] was larger than that found with [TSP] [23]. The fraction of [P\({}_{\rm h}\)] in [P\({}_{\rm c}\)] decreased, and was less than one-third in the winter of 2018, although the average [P\({}_{\rm h}\)]/[P\({}_{\rm c}\)] ratio (=\(x\)) was 0.8 (Table 3). The same decreasing tendency in the [P\({}_{\rm h}\)]/[P\({}_{\rm c}\)] ratio was observed in Sapporo and Tokyo/Sagamihara, although the decrease of [P\({}_{\rm c}\)] was very slight (Table 1). Since the Japanese cities in this study with the exception of Kitakyushu are commercial cities, these results suggest that the main contributor to P\({}_{\rm c}\) was vehicles, and that these contributions are decreasing. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Year/Season** & **[P\({}_{\rm c}\)]** & **[P\({}_{\rm h}\)]** & **[P\({}_{\rm l}\)]** \\ \hline \multicolumn{4}{c}{Sapporo} \\  
& 0.41 & 0.26 & 0.15 \\
2005 W & 0.84 & 0.74 & 0.1 \\  & Sagamihara & & \\  
& 4.5 & 2.45 & 2.05 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: [P\({}_{\rm c}\)], [P\({}_{\rm h}\)] and [P\({}_{\rm l}\)] (\(\rm ug\ m^{-3}\)) in 10 cities in summers (S) and winters (W) from 1997 to 2018. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Year/Season** & **[P\({}_{\text{c}}\)]** & **[P\({}_{\text{h}}\)]** & **[P\({}_{\text{l}}\)]** \\ \hline  
& 2.2 & 0.8 & 1.4 \\ \hline \hline \end{tabular} [P\({}_{\text{c}}\)] was calculated from \(y\) and both [P\({}_{\text{h}}\)] and [P\({}_{\text{l}}\)] were calculated from \(x\) in Table S3. Blank means not calculated.  
\end{table} 
Table 2: Annual, summer, and winter [P\({}_{\text{c}}\)] (\(\text{$\text{$\text{$\text{$\text{$\text{$\text{$\text{$\text{$\text{$\text{$ $\text{$\text{$\text{$\text{$}}$}$}$\text{$0}}}}}}$\text{$1}}\)) in 10 cities with winter/summer ratios. Figure 2 shows the profiles of [TSP] and [P\({}_{\rm c}\)] in Kitakyushu. The levels of [TSP] and [P\({}_{\rm c}\)] were similar to those in Kanazawa, but no decreasing trend was observed in [P\({}_{\rm c}\)]. This figure shows that [P\({}_{\rm l}\)] was higher than [P\({}_{\rm h}\)], which was different from Kanazawa (Figure 1).