| dc.description.abstract | In recent years, the rapid population growth in urban areas of Taiwan has led to a continuous increase in the number of motor vehicles. Consequently, aside from existing stationary sources such as power plants, technology parks, and industrial zones, emissions from motor vehicles have increasingly impacted air quality. Black Carbon (BC) primarily originates from incomplete diesel combustion in heavy-duty vehicles like trucks, lorries, and buses. Carbon Monoxide (CO) mainly comes from the incomplete combustion of gasoline in light-duty vehicles such as cars and motorcycles. Carbon Dioxide (CO2) results from the complete combustion of motor vehicles. Therefore, comparing and analyzing BC, CO, and CO2 pollutants can help understand the area′s traffic emissions characteristics.
This study conducted real-time observations and analysis on major roads in the metropolitan areas of Taipei and Taichung. In Taipei, the observation period was from October 2022 to November 2023, with the location near National Taiwan University adjacent to Keelung Road. In Taichung, the observation period was from September 2017 to April 2018, near Tunghai University adjacent to Taiwan Boulevard. During the observation period, the average concentrations of BC, CO, and CO2 in Taipei were 1.18 µg/m3, 0.95 ppm, and 439.6 ppm, respectively. In Taichung, the average concentrations of BC, CO, and CO2 were 2.47 µg/m3, 0.64 ppm, and 429.7 ppm, respectively. The differences in BC and CO concentrations between the two areas are attributed to different background environments, traffic flows, and vehicle types.
BC, CO, and CO2 concentrations peaked during rush hours, indicating a significant impact from commuter traffic. There was a noticeable downward trend in BC and CO concentrations on holidays, showing the influence of the holiday effect in both areas, with a more pronounced decline during commuting hours compared to other times. During day and night variations, ΔBC/ΔCO in both Taipei and Taichung exhibited low values during commuting hours, with CO showing greater variability than BC. This suggests that CO is the primary traffic emission during these times, and the proportion of gasoline vehicles is higher in these areas compared to other cities, resulting in more CO emissions. The correlation among the three pollutants also shows a larger ΔBC/ΔCO slope during peak hours, indicating a greater variation in CO, which is a primary emission source in both areas. ΔBC/ΔCO2 and ΔCO/ΔCO2 showed high values from noon to afternoon due to photosynthesis consuming CO2, leading to lower CO2 values and thus higher ratios during this period.
During seasonal changes, the ΔBC/ΔCO ratio and temperature at the Taipei and Taichung monitoring stations show a negative correlation trend. This is because vehicle engines efficiency is affected by ambient temperature; the higher the temperature, the lower the combustion efficiency, resulting in more incomplete combustion pollutants. Therefore, during the observation period, CO emissions were more significant at the Taipei and Taichung stations. | en_US |