## 3 Results
### Estimation of PM Reduction Effects by Crops  
To calculate the cumulative PM reduction according to the cultivation of experimental crops, we utilized PM reduction coefficients, canopy variations due to crop growth, and rainfall frequency. The PM reduction coefficient was determined through wind tunnel experiments targeting fully grown crops, but the canopy changes during the cultivation period due to crop growth and planting density. To reflect the crop density and the height, growth curves were derived based on the previous studies on the height of crops such as tritticale and barley and the measured height of crops in the field [34]. The growth stages used average values by month, and the crops, sown in October, grew about 1 m height by the time they were harvested the next June (Figure 10). Rainfall frequency was analyzed from meteorological data for the Saemangeum reclaimed land, the experimental area, from October 2021 to June 2022. Fine dust can reduce the amount in the air by adhering to the crop surface and then being washed away by rainfall, repeating this process until the next rainfall. After sufficient rain washes away the fine dust on the crop surface, it can have a reduction effect again, like a washed filter; hence, rainfall frequency was calculated through weather analysis. The frequency of rainfall was calculated based on the monthly frequency of days when more than 0.5 mm of rain per hour was recorded, reflecting the measurement level of rain gauges. It was counted as one occurrence when it rained continuously for several hours or days. \begin{table}
\begin{tabular}{c c c c} \hline
**Crop** & **Density** & **PM-2.5** & **PM-10** \\ \hline \multirow{3}{*}{Triticale} & Sparsely & 7.0 & 34.0 \\  & Moderately & 120.0 & 82.2 \\  & Densely & 254.7 & 400.3 \\ \hline \multirow{3}{*}{Barley} & Sparsely & 3.1 & 9.5 \\  & Moderately & 14.5 & 26.9 \\ \cline{1-1}  & Densely & 15.2 & 92.7 \\ \hline \end{tabular}
\end{table} 
Table 1: PM reduction coefficients for PM-2.5 and PM-10 by crop types and planting densities, converted based on real-time concentration differences before and after crop canopy in the chamber experiments (unit: mg/m\({}^{3}\)). Figure 9: The PM reduction effect of triticale over time, determined based on the difference in PM concentration before and after passing through the crop zone with difference crop sowing densities. (**a**) Densely triticale sowing, (**b**) Moderately triticale sowing, (**c**) Sparsely triticale sowing, (**d**) Densely barley sowing, (**e**) Moderately barley sowing, (**f**) Sparsely barley sowing. To calculate the cumulative overall PM reduction with triticale and barley during the cultivation period, the cumulative reduction of fine dust was calculated based on the crop canopy, rainfall frequency, and PM reduction coefficient for eight months after the leaves came out (Figure 10). The PM reduction was calculated considering the crop canopy and weather conditions during the cultivation period in the experimental reclaimed land. The PM reduction in agricultural fields according to the crop types and densities was determined monthly using Equation (1) and accumulated over the cultivation period to calculate the total reduction effect. Based on the monthly average height of the crop (\(h_{c}\), m) and the area of the agricultural field (\(A\), m\({}^{2}\)), the crop canopy (m\({}^{3}\)) was determined. This was then multiplied by the reduction coefficient for each crop (\(R_{crop}\), mg/m\({}^{3}\)-time) in Table 1 and the frequency of rainfall (\(F_{rain}\), time/month) to make the monthly PM reduction amount. \[PM\ reduction=\Sigma\big{(}h_{c}\times A\times R_{crop}\times F_{rain}\big{)} \tag{1}\]  
The monthly PM reduction was accumulated to calculate the PM reduction during the crop cultivation period (Figure 11). Comparing triticale and barley, which are cultivated during the same period, triticale, which has relatively more hairs, showed a greater reduction in PM.