| Summary: | 碩士 === 雲林科技大學 === 環境與安全工程系碩士班 === 96 === Student：Wei-tai Chen
Advisor：Chu-chin Hsieh
Volatile organic compounds (VOCs) are one of ozone formation precursors and the rate of emission of biogenic VOCs (BVOCs) by vegetation would be affected by environmental parameters, and the flux would also vary with different plant species. Two micrometeorological techniques, multi-pumps relaxed eddy accumulation (MPREA) and vertical gradient (VG), are developed to measure the flux of BVOCs at altitude of 1200-m in mid-Taiwan. Moreover, the results of MPREA and VG could confirm with each other for attesting to the system’s stability. Eddy diffusivity coefficient (EDC) at atmosphere is calculated by VG and proved its rationality. The range of effective fetch at the sampling site is estimated using the available equations to evaluate the influence area of this study. The BVOC flux measured at two different seasons are related well with environmental parameters including temperature, humidity, and photosyn- thetically active radiation (PAR).
EDC calculated using Valentine approach integrated with the results of MPREA and VG. EDC vary with time and locations due to different environment factors. The result of EDC measured in this study is similar to that of the previous studies. At middle altitudes of 1200-m, the flux of BVOCs measured at day and night are different, the BVOCs flux is 2434 and 1150 (mg m-2 h-1) in day and night, respectively. The BVOCs flux of day is two times higher than that of night because the emissions of BVOCs would raise with temperature and PAR. The flux of BVOCs in spring and winter are 823 and 425 (mg m-2 h-1), respectively. The flux of spring is 2 times higher than that of winter. We conjecture that hexanal, the major species of BVOCs, is emitted by C. Sinensis.
The detection frequency of Isoprene, MACR and MVK have the positive correlate with their flux value. The higher emission frequency of the BVOCs indicate the higher flux of the BVOCs, but β-pinene and Heptanone show opposite correlation. The emission frequency of β-pinene detected in spring indicate 2 times higher than that in winter, but its flux in spring is 2 times lower than in winter. After correlation analysis of environmental factors and species, the result shows that the isoprene and MACR have the better relativity with PAR, and temperature would affect the flux of α-pinene.
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