The Assessment of Phytoextraction Potential of Ten Plain-Planted Tree Species in Cd Contaminated Soils

• Main Authors: Yi-Ying Wu, 吳依縈
• Other Authors: 顏江河
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/40529046921153960805

碩士 === 國立中興大學 === 森林學系所 === 100 === In this study, we planted 10 tree species in cadmium-contaminated farmland to assess the potential of their phytoextraction. The experimental field is supervised by the Changhua County government, and the planted species included Melia azedarach, Sapium sebiferum, Zelkova serrata, Pistacia chinensis, Sapindus mukorossii, Swietenia macrophylla, Koelreuteria formosana, Elaeocarpus decipiens, Michelia compressa var. formosana and Podocarpus macrophyllus. The seedlings were divided into three grades according to growing conditions to find out whether there were differences in accumulated concentraction or amount at the same grade and the same tree species. Twelve months after planting the seedlings in the experimental field, we examined the nitrogen, phosphorus and cadmium concentrations in the plant tissues, and the soil pH and its cadmium level. We next chose the tree species which were most suitable for phytoextraction and evaluated their capacities to reduce the cadmium concentration in the soil by measuring bioconcentration factor (BCF), translocation factor (TF) and the amount of cadmium in plant tissues. The plants grown in the experimental field did not lack of nitrogen and phosphorous nutrients. The results indicated no significant correlations between cadmium concentrations in roots and seedling growth grades. However, the cadmium concentrations in stems and leaves increased as growth grades increased for some tree species, but decreased as growth grades increased for others. The locations of the accumulated cadmium varied from species to species. The third growth grade Melia azedarach accumulated approximately 1,891.45 g ha-1 y-1 of cadmium in their shoots, the highest amount of accumulation among all the planted species. Both the BCF and TF of the Elaeocarpus decipiens were greater than one. Taking the amounts of accumulated cadmium and the BCF and TF consideration, Melia azedarach, Zelkova serrata, Sapium sebiferum, Koelreuteria formosana and Elaeocarpus decipiens were most suitable for phytoextraction. In terms of the soil, soil pH was higher after the experiment than before in the topsoil (0~15 cm), subsoil (15~30cm) and rhizosphere, and the cadmium concentration in each soil layer differed from species to species. Although there were no significant differences in soil cadmium before and after the experiment, there was a negative correlation between soil cadmium concentration and soil pH.