## 3 Results
### Changes in PM According to Mist Spraying at CRP  
At CRP, the average real-time \(\rm PM_{10}\), \(\rm PM_{2.5}\), and \(\rm PM_{1.0}\) concentrations caused by mist spraying increased three to five times compared with those before the mist spraying (Figure 4a). After the mist spraying ended, the PM concentration returned to the PM values before mist spraying. The concentration variation of \(\rm PM_{10}\) was lower than those of \(\rm PM_{2.5}\) and \(\rm PM_{1.0}\) during the evening rush hour, whereas the concentration variation of \(\rm PM_{10}\) was large during the morning rush hour and lunch. However, after mist spraying, the PM ratio was the same as before (Figure 4b). Moreover, during the evening rush hour, \(\rm PM_{2.5}\cdot PM_{10}{}^{-1}\) and \(\rm PM_{1.0}\cdot PM_{10}{}^{-1}\) increased, and \(\rm PM_{1.0}\cdot PM_{2.5}{}^{-1}\) decreased as mist was sprayed. During the morning rush hour and lunch, \(\rm PM_{2.5}\cdot PM_{10}{}^{-1}\), \(\rm PM_{1.0}\cdot PM_{10}{}^{-1}\), and \(\rm PM_{1.0}\cdot PM_{2.5}{}^{-1}\) were reduced. When spraying mist, \(\rm PM_{10}\), \(\rm PM_{2.5}\), and \(\rm PM_{1.0}\) concentrations were 5.4-, 2.9-, and 2.4-fold higher than before spraying, respectively, and returned to the previous concentration after spraying (Table 3). The change in \(\rm PM_{10}\) concentration was lower than those in \(\rm PM_{2.5}\) and \(\rm PM_{1.0}\) during the evening rush hour. There was a significant decrease in \(\rm PM_{2.5}\cdot PM_{10}{}^{-1}\), \(\rm PM_{1.0}\cdot PM_{10}{}^{-1}\), and \(\rm PM_{1.0}\cdot PM_{2.5}{}^{-1}\) after mist spraying. The \(\rm PM_{10}\) concentration changes were on average 2.4 times larger than those of \(\rm PM_{2.5}\) and \(\rm PM_{1.0}\) during the morning rush hour and lunch. After mist spraying, \(\rm PM_{2.5}\cdot PM_{10}{}^{-1}\) and \(\rm PM_{1.0}\cdot PM_{10}{}^{-1}\) decreased, whereas there was no significant difference in \(\rm PM_{1.0}\cdot PM_{2.5}{}^{-1}\) in the Tukey HSD procedure (\(p<0.05\)). These results indicate that the concentration of PMx changed during mist spraying at all times, and the five items of PM concentration ratio were significantly lowered during evening rush hour, morning rush hour, and lunch time at Cheongdam Road Park (CRP). So, the mist spraying could affect the change in concentration and ratio of PMx, but the effect differed at the time. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Time**} & **Mist** & \(\rm PM_{10}\) & \(\rm PM_{2.5}\) & \(\rm PM_{1.0}\) & & & \\ \cline{3-8}  & **Spray** & & \(\rm\mu g/m^{3}\) & & & & \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} Evening \\ Rush hour \\ \end{tabular} } & Before & 27.0(\(\pm\)2.4) b & 8.4(\(\pm\)0.6) b & 4.3(\(\pm\)0.3) b & 0.33(\(\pm\)0.01) a & 0.17(\(\pm\)0.01) a & 0.51(\(\pm\)0.00) a \\  & During & **53.7(\(\pm\)5.8) a** & **21.0(\(\pm\)3.3) a** & **9.1(\(\pm\)1.2) a** & 0.39(\(\pm\)0.04) a & 0.18(\(\pm\)0.01) a & 0.46(\(\pm\)0.02) b \\  & After & 33.0(\(\pm\)3.7) b & 11.6(\(\pm\)1.4) b & 5.3(\(\pm\)0.5) b & 0.37(\(\pm\)0.02) a & 0.18(\(\pm\)0.01) a & 0.47(\(\pm\)0.01) ab \\ \hline \multirow{3}{*}{
\begin{tabular}{c} Lunch \\ \end{tabular} } & Before & 13.2(\(\pm\)0.5) b & 4.3(\(\pm\)0.1) b & 2.2(\(\pm\)0.0) b & 0.34(\(\pm\)0.01) a & 0.18(\(\pm\)0.01) a & 0.52(\(\pm\)0.00) a \\  & During & **67.1(\(\pm\)2.1) a** & **11.5(\(\pm\)1.5) a** & **6.5(\(\pm\)0.7) a** & 0.27(\(\pm\)0.02) b & 0.15(\(\pm\)0.01) a & 0.54(\(\pm\)0.00) a \\  & After & 14.2(\(\pm\)0.7) b & 4.2(\(\pm\)0.1) b & 2.2(\(\pm\)0.0) b & 0.32(\(\pm\)0.01) ab & 0.17(\(\pm\)0.00) a & 0.53(\(\pm\)0.00) a \\ \hline \end{tabular}
\end{table} 
Table 2: The concentrations (mean \(\pm\) S.D., \(\rm\mu g/m^{3}\)) and PM concentration ratio (mean \(\pm\) S.D.) among the three experiments (before, during, and after spraying) during the evening rush hour and lunch hour in the Yangjae Citizen’s Forest (YCF).