| Summary: | 碩士 === 國立屏東科技大學 === 環境工程與科學系所 === 96 === Total amounts of heavy metal in soils can not be the concentrations in plants. Only the heavy metal that is dissoluble or weakly absorbed on the soild surface of the soil was absorbed by plant. Single or sequential extraction methods have been used to estimate the bioavailability of heavy metals for crops, but different degree of soil pollution and several kinds of crops have various extraction methods. Therefore, this study used six traditional single chemical extraction methods (H2O, HCl, NaNO3, CaCl2, EDTA and DTPA) and pot experiment of Chinese cabbage (Brassica chinensis L.) to explore the concentrations of heavy metals (Cd, Cr, Cu, Ni, Pb, Zn, Fe and Mn) in twenty-two agricultural soils of Taiwan, and to evaluate the phytoavailability of the metals considered with the effects of the soil properties by empirical models. Results indicated that the extractability of reagents were found in order: HCl＞EDTA＞DTPA＞CaCl2＞NaNO3＝H2O. Mean concentrations of the heavy metal in Chinese cabbage were found in order: Fe＞Zn＞Mn＞Ni＞Cr＞Cu＞Cd＞Pb. The concentrations of heavy metals in the roots were higher than those in the shoots, while the most mobilizable metals are Cd, Zn and Mn in the plant. No significant correlation between all of the extraction amount and plant uptake for the metals. However, better correlation was obtained when the pH value and clay content of the soil were involved to predict the heavy metal concentrations in Chinese cabbage. Therefore, consideration both the total metal concentrations and soil properties (pH and clay) for different extraction methods, good correlation between the concentrations of Cd, Mn and Pb in all of the extraction methods and concentrations in shoot of Chinese cabbage can be established.
Keywords: heavy metal, phytoavailability, Chinese cabbage, single chemical extraction, soil
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