| dc.description.abstract | The current air quality model requires temporal distribution of the emissions inventory provided by the Taiwan Emission Data System (TEDS), released by the Ministry of Environment, according to their monthly, daily, and hourly characteristics to provide pollution emission scenarios. The current method does not account for the misestimation caused by consecutive holidays in the monthly characteristics and does not provide corresponding emissions changes for significantly variable highway traffic during consecutive holidays.
This study utilizes high-resolution traffic volume data provided by the Traffic Data Collection System (TDCS) for national highways, calculates the traffic volume information corresponding to vehicle types and counties, and prioritizes the removal of the impact of consecutive holiday days before performing the weighting calculations. First, an emission scenario without consecutive holidays is created, and daily emission multipliers for various types of consecutive holiday characteristics are provided, allowing flexible adjustment of holiday emissions.
After correcting the temporal distribution of emissions, NOx emissions during the consecutive Chinese New Year holidays decrease by approximately 0.13 tons per hour on average, while NMHC emissions increase by about 0.03 tons in the areas south of Hsinchu and Miaoli. During February on non-consecutive holidays, NOx emissions increase by approximately 0.04 tons per hour, and NMHC emissions decrease by about 0.03 tons. These changes in the emission scenario align with the actual traffic volume, such as the reduction of NOx emissions due to fewer heavy trucks during holidays and the increase in NMHC due to more private car trips, proving that this temporal distribution method can better interpret the actual highway emissions in the model.
After updating the highway temporal distribution method, the impact on the air quality model includes changes in primary pollutants NOX and NMHC as well as secondary pollutants O3 and PM2.5. The main concentration changes occur in the western part of the region around highways. During consecutive holidays, NOx reductions are most significant, with decreases reaching 12-30 ppb at 8 A.M. under weak synoptic weather conditions. Since the western region along the highways is VOC-limited, O3 concentrations increase, with daytime concentrations rising by about 2-4 ppb and nighttime by about 1-3 ppb. The reduction in NOx also increases the OH radical concentration in the air, reacting with NMHC and resulting in a decrease in NMHC concentration by about 0.8-1.2 ppb. PM2.5 concentrations decrease due to reduced secondary nitrate formation from NOx and direct emissions of elemental carbon, with daytime simulated concentrations decreasing by 0.8-1.2 μg/m³ and nighttime by 0.8-2 μg/m³.
Comparison with air quality monitoring stations indicates that adjusting the highway emission temporal distribution can improve the overestimation of NOx during holidays, generally reducing overestimation by 1-2 ppb and decreasing RMSE by 1-2. The O3 concentration improves from an initial underestimation by about 1-2 ppb, and RMSE for NMHC and PM2.5 also shows some reduction. | en_US |