Three combined investigations were conducted to examine the sources of PM_2.5 in agricultural areas. The first was the measurement of PM_2.5 and gaseous compounds in the greenhouse, which is a relatively closed system, while the second was the analysis of pesticide components used in agricultural areas. Finally, the physical and chemical properties of PM_2.5 were analyzed in an orchard area and compared with the results of the greenhouse and agricultural chemical analyses. As a result, this research was able to confirm the source of emission and characteristics of PM_2.5 originating from the agricultural area. Volatile organic compounds (VOCs) in agricultural areas are emitted by agricultural chemicals, and the discharged agricultural chemicals are first absorbed into the soil, and then released into the air by evaporation. Finally, the secondary products of PM_2.5 in agricultural areas were estimated to have positive relationships with the VOCs from agricultural chemicals, and NH₃ from fertilizers. The photochemical reactions of VOCs and NH₃ were responsible for the impact on secondary products.