Myoungki Song

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.

This study aims to analyze the seasonal number concentrations corresponding to each particle size derived from the measurements of exhausts from approximately seven million vehicles on real-world using a pair of the scanning mobility particle sizer to determine the vehicle emission rate. The actual tunnel flow coefficient was investigated for car emission rate based on the measurements of individual physical parameters (i.e., cross section area and length of the tunnel, tunnel wind speed and traffic volume). The mode of particle diameter according to temperatures in respective seasons exhibited a high correlation together with rapid changes at temperature above the breakthrough point. The temperature acted as major cause of determination of final condensation diameter, which is also dependent on diverse environmental effects comprising particle number concentration. The traffic volume of ordinary cars increased by more than twice as much in the period of Asian New Year, the traffic volume of buses/RVs/trucks decreased by more than 25% during weekdays. As a result, the particle number concentration discharged from a unit vehicle was 6.96 × 10¹² N/veh·km during weekdays, and the values of weekends appeared as 6.08 × 10¹² N/veh·km. The overall averaged particle number concentration based on the actual seasonal road measurements shows 5.82 × 10¹² N/veh·km.

Polycyclic aromatic hydrocarbons (PAHs), an important class of hazardous airborne pollutants, are mutagenic and carcinogenic substances known to be released during the paving of asphalt. In this study, PAHs emitted from an asphalt mix plant were analyzed to investigate the effects on a suburban residential area. Black carbon, organic carbon, elemental carbon, and PAHs in fine particulate matter (PM_2.5) were analyzed in a village near the asphalt mix plant. The results of wind direction analysis revealed that the village was meteorologically affected by emissions from the asphalt mix plant. PAHs in PM_2.5 ranged from 0.51 to 60.73 ng/m³, with an average of 11.54 ng/m³. Seasonal PAHs were highest in winter, followed in order by spring, autumn, and summer. The diagnostic ratios between PAHs indicate that the source of PAHs could be incomplete combustion of petrogenic origin. The maximum black carbon concentration in the intensive periods reaches up to 14.17 μg/m³ during mix plant operation periods. Seasonal ∑BaP_TEF values based on Toxic Equivalence Factor were: winter (2.284 ng/m³), spring (0.575 ng/m³), autumn (0.550 ng/m³), and summer (0.176 ng/m³). The values are about 6.5 times higher than the concentration in another background area and more than three times higher than those in the capital city, Seoul, in the Republic of Korea. In conclusion, primary emissions from the point source can be considered the major contributor to pollution in the residential area.

To reduce fine particulate matter (PM_2.5) level, the sources of PM_2.5 in terms of the composition thereof needs to be identified. In this study, the experimental burning of ten types of biomass that are typically used in Republic of Korea, collected at the regional area were to investigate the indicated organic speciation and the results obtained therefrom were applied to the chemical mass balance (CMB) model for the study area. As a result, the organic molecular markers for the biomass burning were identified as they were varying according to chemical speciation of woods and herbaceous plants and depending upon the hard- and soft characteristics of specimens. Based on the source profile from biomass burning, major sources of PM_2.5 in the study area of the present study appeared as sources of biomass burning, the secondary ions, secondary particulate matters, which is including long-distance transport, wherein the three sources occupied most over 84% of entire PM_2.5. In regard to the subject area distinguished into residential area and on roads, the portion of the biomass burning appeared higher in residential area than on roads, whereas the generation from vehicles of gasoline engine and burning of meats in restaurants, etc. appeared higher on roads comparing to the residential area.