## 3 Results  
### Observation of Gaseous Components and Analysis of Agricultural Chemicals in Greenhouse  
To examine the originations of PM\({}_{2.5}\) in agricultural areas, three different experiments were performed. The first was to measure PM\({}_{2.5}\) and precursor gases in the greenhouse, which is a relatively closed system, compared to the outdoor area. The second was to analyze the components of pesticides, herbicides, and vapor deposition agents used in the agricultural source. Finally, by measuring the characteristics and precursors of PM\({}_{2.5}\) in an outdoor area, the source of PM\({}_{2.5}\) in agricultural areas could be defined. For this purpose, PM\({}_{2.5}\), NO, NO\({}_{2}\) and NH\({}_{3}\) were studied for 28 days in greenhouses in the Wanju area (Figure 1), and four different kinds of pesticides, germicides, herbicides, and vapor deposition agents were used to analyze the characteristics of PM\({}_{2.5}\) at orchards of the Jangsu area. Figure 4 shows the results of PM\({}_{2.5}\), NO, NO\({}_{2}\) and NH\({}_{3}\) measured at the Wanju greenhouses. The average concentration of PM\({}_{2.5}\) observed during the study period was 12.98 \(\mathrm{\SIUnitSymbolMicro\text{g}}\)/\(\mathrm{m}^{3}\), the average concentration of NO was 8.11 ppb, the average concentration of  
Figure 3: GC-MS chromatogram of the volatile organic compounds (VOCs) released by thermal desorption. Figure 2: Picture of air monitoring trailer and schematic of the air monitoring instruments and samplers in the air monitoring trailer. NO\({}_{2}\) was 15.11 ppb, and that of NH\({}_{3}\) was 101.34 ppb. In addition, the maximum concentration observed during the measurement period of PM\({}_{2.5}\) was 29.96 ug/m\({}^{3}\), and those of NO, NO\({}_{2}\), and NH\({}_{3}\) were 55.06, 183.62 and 309.27 ppb, respectively. According to the monthly atmospheric report of Jeonbuk province in October 2020 from the urban atmospheric measurement network data of the monthly atmospheric report, the average concentration of PM\({}_{2.5}\) was 17 ug/m\({}^{3}\), and the maximum concentration over 24 h was 32 ug/m\({}^{3}\), while the average concentration of NO\({}_{2}\) was 9 ppb, and the maximum concentration during 24 h was 12 ppb. Comparing the monthly atmospheric report to the measurements of this study, the concentration of PM\({}_{2.5}\) was similar, while NO\({}_{2}\) was 1.7 times higher than the local concentration on average, and more than 20 times higher at maximum. The concentration of ammonia is not shown in any publication of the same province. When comparing the 6.9 ppb of NH\({}_{3}\) concentration in Seoul suggested in the previous study, NH\({}_{3}\) in the research area was 14.7 times higher than the average concentration, and 44.8 times higher than the maximum concentration [21]. That means that the above result shows that the concentration of PM\({}_{2.5}\) in the greenhouse is similar to or lower than the concentration of the local area, but the precursor gases, such as NO\({}_{2}\) and NH\({}_{3}\), are higher than the local concentration. Figure 5 shows the concentrations of PM\({}_{2.5}\), NO, NO\({}_{2}\) and NH\({}_{3}\) measured in the greenhouse over time. PM\({}_{2.5}\) had concentration range of 11.03-15.01 ug/m\({}^{3}\) with standard deviation of 1.23 ug/m\({}^{3}\), which means there was no significant change in concentration over time. On the other hand, NO was in the range 3.76-16.9 ppb, with standard deviation of 3.24 ppb; NO\({}_{2}\) was in the range 9.93-26.77 ppb, with standard deviation of 5.22 ppb; and NH\({}_{3}\) was in the range 78.77-141.54 ppb, with standard deviation of 15.01 ppb, which means that the variation was higher than the variation of PM\({}_{2.5}\). When looking at the concentrations of NO and NO\({}_{2}\) over time, the concentrations of NO and NO\({}_{2}\), which were relatively stable at night and dawn, increased after 7 a.m., and NO showed the maximum concentration at 9 a.m., and then decreased.