| Summary: | 碩士 === 國立雲林科技大學 === 環境與安全工程系碩士班 === 96 === The contributions of biomass smoke to the ambient air in Taiwan are predominantly due to post-harvest burning of rice straw. This study attempts to characterize ambient anhydrosugar tracers derived from rice straw burning. Three particle-size ranges ( PM2.5, PM2.5-10, and TSP ) were collected simultaneously at two locations ( countryside and suburban site ) with harvest season of rice crops in order to investigate the variations of particle-size profiles of molecular tracers in the atmosphere. The study also has broadly examined on seasonal variations of anhydrosugars concentration in soil, as well as on the estimations of biomass burning contribution in PM2.5 particles.
The results shown that the concentrations of anhydrosugars in both PM2.5 and TSP particles significantly increased during the intensive burning periods ( about 5.5 times higher than off-season background; and about 1.21 and 1.40 times higher than harvest-season background in PM2.5 and TSP particles ). Furthermore, the size distribution of ambient levoglucosan was concentrated in PM2.5 ( about 81％ in TSP ) at suburban site; but it was a broad size distribution at countryside, the PM2.5 ( fine ) and PM＞10 ( coarse ) particles constituted 56％ and 35％ in TSP, respectively. The day / night ratios were higher ( day / night ＞1 ) in burning peaks and lower ( day / night ＞1 ) in non-burning peaks. Otherwise, levo / mann ratio was about 54.7 in PM＞10 particles of this study, which is similar to literatures ( about 50 ). Moreover, the concentrations of anhydrosugars in soils increased with the activity of biomass burning and decreased with the rainfall. For the contribution ratios of biomass burning in PM2.5 particles, the ratios at suburban site were generally higher than that at countryside ( average contribution ratios for countryside, and suburban were 10.2％, and 13.5％, respectively. ). This study is the first effort to characterize molecular tracers for rice straw burning in ambient air as well as to reveal important insights into particle-size characteristics of rice straw burning.
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