Metro Kaohsiung with high percentage (6-10 %) of poor air quality (PSI>100) has been announced officially by Taiwan Environmental Protection Administration (TEPA) as the worst air quality region among seven Air Quality Zones (AQZ) in Taiwan. Ozone is one of two major air pollutants that are responsible for the poor air quality. In this study, the vertical concentration profiles of ozone and its precursors (NOX and VOCs) at eight sites were measured by tethered balloons with air pumps and tedlar sampling bags. This method was used to investigate the vertical profile and the tempospatial distribution of ozone and its precursors in offshore/inland regions. This study further investigated ozone formation mechanism and air mass trajectory via simultaneous air quality sampling around the coastal region of metro Kaohsiung.
This study sampled the vertical concentration profiles of ozone and its precursors at both inland and offshore sites during eight intensive sampling periods on August 16-17 and November 2-3, 2006, January 24-25, March 6-7 and May 2-3, 2007, October 30-31, 2008, and March 11-12 and July 15-16, 2009. Eight sampling periods were divided into the sea-land breeze period, the northeast monsoon period, and the mixing wind field period. During the sea-land breeze period, the wind direction changed 90˚ and more between daytime and nighttime, and the wind speeds of the sea breezes varied significantly than those of the land breezes. During the northeast monsoon period, prevailing wind blew from the north (300~60˚) with the average wind speeds of 1~4 m/s. During the mixing wind field period, the wind direction varied significantly from 270˚ to 90˚ with the average wind speeds of 1~3 m/s.
Results obtained from the vertical profiles showed that O3 concentration appeared stratification phenomenon at 40 out of 64 sampling sites, in which its precursors (NOX or VOCs) demonstrated stratification phenomenon at 30 sampling sites, accounting for 75 % of total O3 stratification. It suggested that ozone and its precursors had strong correlation with each other. The linear slope of the titration effect showed that the intensity of titration effect at night during the northeast monsoon period was larger and had higher correlation (R> 0.7), and followed by the mixing wind field period and the sea-land breeze period. This phenomenon correlated closely with meteorological conditions, the concentrations of O3 precursors, and solar radiation intensity. Therefore, O3 concentration at night during the northeast monsoon period was lower than those of the sea-land breeze period.
Results obtained from VOCs measurement indicated that the major species of VOCs was acetone which accounted for 16.25~64.05 % of total TVOCs-C2 in the offshore region. High concentration of TVOCs-C2 was affected by the usage of organic solvents. While, the major species of VOCs in the inland region was toluene which accounted for 6.41~43.77 % of total TVOCs-C2. Furthermore, results obtained from backward trajectory showed that air pollutants emited from land sources could transport to the offshore region, resulting in high concentration of oversea NOX and VOCs. Major species of VOCs for high O3 formation potential were aromatics and vinyls at the height of 0~500 m around the coastal region of metro Kaohsiung.
The control of O3 precursors concentration showed that the ratio of [TVOCs-C2]/[NOX] in the offshore region was higher, indicating that O3 formation was NOX-limited. Therefore, NOX must be controlled for reducing O3 formation. However, the ratio of [TVOCs-C2]/[NOX] in the inland region was lower, some cases even below 4, showing that O3 formation was VOCs-limited. Thus, VOCs must be controlled for reducing O3 formation.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0824110-103536 |
| Date | 24 August 2010 |
| Creators | Liu, Yu-Fu |
| Contributors | Chi-Chi Lin, Yuan-Chung Lin, Chung-Shin Yuan, Chitsan Lin |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0824110-103536 |
| Rights | campus_withheld, Copyright information available at source archive |
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