| Summary: | 碩士 === 國立交通大學 === 環境工程系所 === 102 === This study investigates the toxicity of halogen-substituted pyridines using a closed-system algal toxicity test technique. Three test endpoints (i.e., dissolved oxygen production (ΔDO), final yield and algal growth rate) were applied to examine the toxic effects of various halogen-substituted pyridines. The unicellular green microalga (Pseudokirchneriella subcapitata) was the test organism and 11 halogen-substituted pyridines were the test chemicals. For insoluble chemicals, this research added Acetone in the stock solution and conducted quality assurance with solvent control. The ranking of sensitivity of three endpoints were FY(81.82%) > ΔDO(18.18%) > GR, which means when observing alga cells, the obvious variety can be seen. When comparing the sensitive species, Pseudokirchneriella subcapitata is almost sensitive. Through observing the results in this study, one can figure out the bromo substituent provides more toxicity than other halogen substitutes and the toxicity variation is in accordance to number of substituents and analogues.
Furthermore, the results of QSAR regression analysis show that chemicals in this study have a good correlation with logKow (r2=0.30-0.33). In contrast, regression correlation with Ehomo is even less than ideal (r2=0.82-0.86). But when combining these two parameters, its relevance is still within the acceptable range (r2=0.80-0.84). This means that in the future the QSAR model developed by this study can easily and quickly estimate similar compounds, to save more time and money. Another addition to the objective of this research, was to investigate the mechanism of traditional classification accuracy with Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). The results showed that 2,3-Dichloropyridine、2,5-Dichloropyridine、3,5-Dichloropyridine and 2,3,5-Trichloropyridine did not belong to non-polar chemicals, and where 2,3,5-Trichloropyridine was classified as the reactive substance. Therefore, the use of statistical methods PCA and HCA can systematically combine the physical and chemical properties of the compounds with biological reactions, to further classify modes of toxic action of halo-pyridines.
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