| Summary: | 碩士 === 國立高雄海洋科技大學 === 海洋環境工程研究所 === 99 === According to a report published by EPA in 2009, Kaohsiung and Pingtung area has the poorest ozone air quality among all others throughout Taiwan. The efficacy of improvement in the past 2 decades has not been obvious compared to PM10. Ozone is a product of photochemical reaction, and its precursors include Volatile Organic Compounds (VOCs) and Nitrogen Oxides (NOX). In the past 20 years, models of ozone air quality have assumed the precursor pollutants to be uniformly mixed in the vertical distribution, with no stratification. Recently however, a number of studies have pointed out that the concentration of atmospheric VOCs is affected by weather conditions, season etc., which result in stratification. In order to prove the vertical distribution profile of VOCs, this study used a tethered balloon to collect air samples at the ground level（2m）, and at heights of 100 m, 200 m, 300 m, 400 m, 500 m, 600 m, 700 m and 800 m. The sampling method follows NIEA A715.13B which allows the analysis of 101 VOCs with calibrations using the PAMS（photochemical assessment monitoring system）and the UAT（urban air toxins）standard gases. To observe the vertical stratification of VOCs in northern Kaohsiung, samples were collected at stations set up at National Kaohsiung Marine University（NKMU）and Wen-Fu Elementary School（WFES） simultaneously. To compare the diurnal variation of VOCs vertical distribution, the sampling time were designated in six hour intervals at 12:00, 18:00, 00:00, and 06:00.
The results show that:（1）In terms of seasonal variations, chemicals that yielded 100% detection rates in both summer and winter seasons include toluene, ethyl-benzene,（m, p）-xylene, o-xylene, n-hexane and acetone.（2）In terms of diurnal variations, the highest average concentration at NKMU was found at 12:00 while the lowest was at 06:00; the highest average concentration at WFES was found at 06:00 however, with the difference in patterns possibly due to geographical influences and life styles of local residents.（3）For spatial distribution, acetone had the highest average concentration at both stations during summer, while in winter the two stations yielded dodecane and acetone, possibly due to influences from seasonal winds. （4）In vertical distribution, detection concentrations are mostly higher in the upper atmosphere compared to that near the surface, regardless of day or night. This distribution covers 89.5% of all samples, indicating a sign of stratification of TVOCs-C2, especially at 12:00.（5）With photochemical reactivities, the highest likelihood for ozone production at the NKMU site in summer is at a height of 400 m, while that at WFES is 800 m, the main contributors being toluene and acetone. In winter the highest probability occurs at 500 m for both sites, with BTEX and dodecane as main contributors.（6）Observation of concentration accumulations indicate the possibility of the presence of an inversion layer, leading to a piling up and spreading of pollutants at certain heights. （7）The BTEX ratio demonstrates a high ratio of toluene, which could be caused by automobiles and industrial pollution. （m, p）-X/E ratio shows that surface air mass at NKMU is younger than that in the upper air, with the pollutants mostly from automobiles, while the upper air mass at WFES is younger than that at the surface, with pollutants presumably from nearby petrochemical industries.
The results of this study can be used for the simulation of air quality so that researchers can further grasp the ozone generation and transmission mechanisms. The study also provides suggestions for the government to optimally control pollution sources.
|
|---|
