科研之友
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摘要
The number of vehicles, especially motorcycles, which are the dominant source of Hanoi's air pollution, has rapidly increased in recent decades. To investigate air quality in Hanoi, a 1-week observation of VOCs, CO and O-3 in September 2015 and a year-long campaign to measure O-3, NOx and CO between October 2015 and December 2016 were conducted in the inner city area. Overall mean values of O-3, CO and NO2 mixing ratios were 19.3 +/- 15.3 ppb, 1.3 +/- 0.8 ppm and 21.4 +/- 11.8 ppb, respectively. The O-3 mixing ratio often exceeded the WHO guideline value of 50 ppb (daily 8-h mean). Although less frequently exceeding the WHO short-term (1h mean) guideline of 106 ppb, the observed NO2 overall mean value was greater than the WHO guideline value of 21 ppb. A diurnal profile and analysis of the composition of VOCs indicates that atmospheric VOCs in Hanoi mainly originated from motorcycles, which dominate Hanoi's vehicle fleet. The good correlation between measurements of VOCs and CO also indicates motorcycles as the main source of CO. The NOx/CO ratio, which is specific to a given emission source, was largely unchanged throughout the year, indicating that vehicles including motorcycles as well as buses, trucks and cars are the main source of O-3 precursors year-round. The estimated VOC/NOx ratio of 12 +/- 5 suggests that Hanoi's air quality can be categorized as NOx-limited regime with regards to O-3-formation. Therefore, controlling NOx emissions from not only motorcycles and also other vehicles would be highly effective at decreasing Hanoi's O-3 levels. Furthermore, the results suggest the relationship between the northeast monsoon and an O-3 burst in the winter season.
- 出版日期2018-5
