## 3 Results  
### PM Reduction Coefficient by Wind Tunnel Experiments  
To determine the PM reduction coefficient due to crop absorption, according to cultivation density for triticale and barley, a wind tunnel experiment was performed. After injecting fine dust for a sufficient time, the particulate matter adhered at the crop surface was washed with triple-distilled water, then filtered to precisely measure its weight, thereby determining the adsorption amount. Figure 8 represents the results, converted into the amount of particulate matter absorbed per hectare for triticale and barley. Based on moderately sowing, the particulate matter absorption amount of the crop showed that triticale was about 1.21 times higher than barley, and based on densely sowing, it was 1.34 times higher. Triticale could reduce more particulate matter as it has more crop hairs on its surface, and thus, a relatively larger adsorption surface area. Analysis results according to planting density showed that in the case of sparsely sowing, triticale decreased by 50.0% and barley by 79.8% in particulate matter absorption amount. This is because when crops are sparsely planted, the number of crops that can adsorb particulate matter decreases, space occurs between the crops, and the shaking range of the crops increases, causing the amount of resuspended particulate matter to increase, thus sharply lowering the reduction efficiency. However, triticale showed a 3.02 times higher reduction effect compared to barley, even in sparsely sowing, because the hairs on the surface reduced the amount of resuspension. The PM reduction coefficient of the crops by the gravimetric method was derived as 2233 g/ha for triticale and 1839 g/ha for barley, based on moderately sowing. However, it is calculated based on the crop cultivation area, so it cannot take into account the changes in canopy due to the growth of the crops. The second method to determine the PM reduction coefficient is to analyze the real-time concentration of airborne fine dust before and after passing through the crop zone. The incoming air from the outside to wind tunnel was used to calibrate the data, and through the wind tunnel experiments on the planting density of triticale and barley, the difference in PM-10 and PM-2.5 concentrations before and after the crop zone was presented over time (Figure 9). Because the experiment started with crops that were completely washed and dried, a large amount of fine dust was absorbed initially after the start of the experiment, showing a high PM reduction amount. As time passed, the reduction amount of fine dust  
Figure 8: The PM reduction coefficient based on measuring the fine dust attached to the surface of crops using the gravimetric method according to two crops (triticale and barley) and its cultivation density. showed a decreasing trend in a logarithmic graph. After a certain time, a section where the reduction amount of fine dust of crops became constant appeared. When the crops were densely installed, it took more time for the reduction concentration to reach 0 due to more fine dust being able to be absorbed at the crop surface. The reduction amount over time at the bottom of the graph was integrated to derive the PM reduction coefficient for each crop and planting density (Table 1). The PM reduction coefficient for each crop was calculated based on the amount of fine dust absorbed by the crop canopy, and this can be used to calculate the amount of PM reduction in the entire agricultural land. The PM reduction coefficient for tritticale, depending on whether the planting density was sparse, moderate, or dense, was 7.0, 120, and 254.7 mg/m\({}^{3}\) for PM-2.5, and 34.0, 82.2, and 400.3 mg/m\({}^{3}\) for PM-10, respectively. In the case of barley, it was 3.1, 14.5, and 15.2 mg/m\({}^{3}\) for PM-2.5, and 9.5, 26.9, and 92.7 mg/m\({}^{3}\) for PM-10, respectively. At general sowing intervals, tritticale showed a higher PM reduction coefficient than barley, with PM-2.5 being 8.3 times higher and PM-10 being 3.1 times higher.