| Summary: | 碩士 === 國立中央大學 === 化學學系 === 101 === Near-surface ozone is one of the key pollutants in most countries. Ozone is a secondary pollutant produced from photochemistry. It is formed via reactions involving NOX and volatile organic compounds (VOCs) in the presence of sunlight. NOx and VOCs together are called “ozone precursors”. Therefore, the abatement of precursors at minimum social and economical cost will be the key to reduce surface ozone and to improve air quality. However, VOCs are a collective term composing hundreds of thousands of airborne compounds with a wide range of ozone formation potentials (OFPs). As a result, it is not only economically viable but also sensible to only target species of high OFPs and abundance.
VOCs emissions in the Taoyuan area consist of two major sources of traffic and industrial emissions. As a key part of a collective field campaign aiming at reducing ozone in Taoyuan county, an on-line VOCs monitoring system was set up in Taoyuan city during 9/14/2012 - 11/23/2012 to investigate the composition and levels of more than 50 VOCs in a traffic ridden environment with hourly resolution. Moreover, off-line flask sampling in seven surrounding industrial parks was also performed to shed light to VOCs of industrial nature.
Two methods of maximum incremental reactivity (MIR) and relative consumption were used to reveal the critical VOCs to form ozone. High OFP VOCs such as propylene, ethylene and 1,2,4-trimethylbenzene were found to be significant with the city measurements. In the industrial parks, high levels of oxygenated VOCs (OVOC), especially acetaldehyde were observed. In one example (中壢工業區), OVOC can contribute more than 70% of the total VOCs level, and acetaldehyde alone can contribute as high as 80% in ozone formation. As a result, the role of ambient aldehyde as a primary pollutant and its possible removal from the industrial processes due to its strong OFP and toxicity is worth investigation.
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