An Investigation of Urban Air Pollution in Xi'an, China
Abstract
As the world's urban population continues to grow, the environmental problems associated with large population centers continue to be exacerbated. Because of this, understanding the environmental impacts of the world's large urban areas is becoming more and more important, especially in areas of the world for which limited data exists. In this study, measurements of a suite of air pollutants were made in Xi'an, China in August of 2011, to assess the concentrations and emission trends of air pollutants in an emerging Chinese megacity. The study site was located on the campus of Jaiotong University, with the sampling inlet positioned at the top of a 23 meter scaffold tower which was on top of a 100 meter tall building. In this study, measurements of nitrogen oxides (NOx) were made by chemiluminescence, measurements of carbon monoxide (CO) and ozone (O3) were made by absorption spectroscopy, and measurements of volatile organic compounds (VOCs) were made by proton transfer reaction mass spectrometer (PTR-MS). CO, O3, and VOC data were taken for approximately three weeks, while NOx data were taken for ten days at the end of the campaign. VOC data was in the form of low frequency mass scans for the first half of the campaign and of high frequency measurements of acetaldehyde, benzene, and toluene for the second half. The diel trends in the mixing ratios of CO, NOx, acetaldehyde, benzene, and toluene displayed an increase at sunrise associated with morning vehicle traffic, a maximum in the mid morning and a minimum in the late afternoon. Ozone mixing ratios displayed the trend typical to urban areas, increasing after sunrise to a maximum in the late afternoon and decreasing to a minimum in the early morning. CO-to-NOx molar ratios were calculated by plotting CO against NOx and creating a linear fit to the data. This linear fit had a slope of 12.2 and an R2 of 0.39. This ratio is greater than what is typically observed in US cities. Data from the Xi'an campaign were compared to a previous campaign in Mexico City, Mexico to contrast relative abundances of CO, NOx, and VOCs.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A11F0108J
- Keywords:
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- 0345 ATMOSPHERIC COMPOSITION AND STRUCTURE / Pollution: urban and regional;
- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: composition and chemistry