Comparison of the Regional Impacts of Aircraft Emissions at Major International Airports in Korea on Ozone

The impacts of aircraft emissions at three major international airports (Incheon, Gimpo, and Jeju) in South Korea on regional ozone (O3) concentrations were evaluated using a high resolution numerical modeling approach. In addition, a process analysis (PA), including the integrated process rate (IPR) and integrated reaction rate (IRR), was used to quantify the contributions of the individual physical and chemical processes to the production or loss of O3 in the study area. In this study, the numerical modeling was applied to two different atmospheric conditions that include (1) urban pollution sources surrounding Incheon (RKSI) and Gimpo international airports (RKSS) and (2) less polluted sources surrounding Jeju international airport (RKPC). For the simulation, high O3 concentration days (about 100 ppb on both 17 August for the RKSI-RKSS and 2 August for the RKPC) during the summer of 2010 were selected. The regional impacts of aircraft emissions during the simulation day were simulated to allow comparison both with the impact of aircraft emissions (i.e., TOTAL case) and without such effect (i.e., BASE case) for the RKSI-RKSS and RKPC, respectively.

The line sources of pollutant gases emitted from commercial aircrafts within the boundary layer (between ground level and 1 km) at the RKSI-RKSS and RKPC airports were estimated using the number of landing and take-off (LTO) and the Emissions and Dispersion Modeling System (EDMS). The EDMS provides the emission factors of chemical species (e.g., NOx, VOC, CO, SOx, and 394 speciated organic gases) according to aircraft types and operational modes (taxi-in and out, start-up, approach, take-off, climb-out, and cruise). The emissions for taxi-in and out, take-off, and start-up modes were estimated from the ground-level of three airports, whereas those for approach and climb-out modes were estimated using the vertical emission profile within the boundary layer, which were calculated from each air route over the three airports. The emission data was then applied to the 3-D chemical transport model. The model study suggested the possibility that aircraft emissions in the target area can exert a significant impact on the O3 concentrations in the source areas as well as their surrounding/downwind areas. The negative impacts (approximately -5 ppb) of aircraft emissions on the daytime O3 concentrations were predicted to be near the airport areas (the RKSI-RKSS and RKPC), due to both the high NOx emissions with the high NOx/VOC ratio and meteorological conditions (e.g., wind field patterns). During the late afternoon through night, their maximum negative impacts (approximately -20 and -10 ppb for the RKSI-RKSS and RKPC, respectively) occurred at the airports followed by the downwind regions of the airports, possibly due to the fast titration of O3 by NO. Conversely, the positive impact (O3 increase of about less than 2 ppb) of aircraft emissions on O3 concentrations occurred in the downwind regions of each airport during the day.

According to IPR analysis of O3 during the study period, the chemical process at each airport (RKSI, RKSS, and RKPC), where the decrease in O3 concentrations was dominant, made the largest contribution to the differences in O3 concentrations between the TOTAL and BASE cases (i.e., due to the impact of aircraft emissions) compared to the other physical processes (e.g., horizontal and vertical advection/diffusion). The results of IRR analysis indicated that the rates of photochemical O3 production and net O3 production at most sites of the model domain for the TOTAL case were slightly lower than those for the BASE case. Unlike the rate of O3 production, the differences in the rates of photochemical O3 destruction at most sites (especially, the airports) were slightly higher in the TOTAL case than the BASE case. These negative impacts might lead to the decrease in the O3 concentration at and/or around the airports in the study area. This study confirmed that aircraft emissions near airport areas can affect the air quality (e.g., O3 and NOx) at the airports as well as their surrounding/downwind regions.

Acknowledgments This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2013R1A1A4A01012837).