| 摘要: | 近年台灣都會地區人口快速地增長，機動車輛數目也隨之持續成長，除了該地區既有之固定源，如火力發電廠、科技園區、工業區等等，機動車輛所排放之污染物也對空氣品質愈趨影響。其中黑碳(BC)主要來自柴油之不完全燃燒，如卡車、大貨車及公車等重型車輛；一氧化碳(CO)主要來自汽油之不完全燃燒，如小客車及機車等輕型車輛；二氧化碳(CO2)主要來自機動車輛之完全燃燒。因此，針對BC、CO及CO2三種污染物進行比較及分析，有助於了解該地區交通排放特性。
本研究於台北及台中兩大都會區的重要幹道進行即時觀測解析，台北測站觀測期間為2022年10月至2023年11月，地點位於台灣大學環工所旁之監測貨櫃，緊鄰基隆路；台中測站觀測期間為2017年9月至2018年4月，地點位於東海大學旁，緊鄰台灣大道。觀測期間，台北測站之BC、CO、CO2平均濃度分別為1.18 µg/m3、0.95 ppm及439.6 ppm；台中測站分別為2.47 µg/m3、0.64 ppm及429.7 ppm，為兩站不同背景環境及不同車流、車種等因素造成BC及CO濃度存在差異。BC、CO及CO2濃度在尖峰時段有高值，明顯受到上下班車潮之影響。假日之BC及CO濃度皆有下降的趨勢，顯示兩站皆受到假日效應之影響，尤其在上下班時間，下降幅度相較其他時段更為明顯。
日夜變化中，台北及台中兩站ΔBC/ΔCO在上下班時間皆出現低值，並發現CO變化量幅度勝於BC，說明CO在上下班時段為主要交通排放源，且兩站汽油車站比皆高於其他城市，CO之排放相較更多。在三種污染物之相關性中也顯示尖峰時段ΔBC/ΔCO斜率較大，代表CO變化量較大，皆為兩站之主要排放源。兩站之ΔBC/ΔCO2及ΔCO/ΔCO2在中午至下午間出現高值，因其光合作用消耗CO2造成CO2低值，而使比率在此時出現最高值。在季節變化中，台北與台中測站ΔBC/ΔCO與溫度呈反相關之趨勢，因車輛引擎會受環境溫度影響其燃燒效率，溫度愈高，燃燒效率愈低，產生更多不完全燃燒污染物，因此台北及台中測站於觀測期間CO排放較為顯著，主要移動污染來源為汽機車。
;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. |
