토양환경 분야PS-03 : 밭토양에서 소석회와 패화석에 의한 카드뮴 부동화 효과의 비교 = Comparison of Effects of Calcium Hydroxide and Oyster Shell on Cadmium Immobilization in Upland Soil

다국어 초록 (Multilingual Abstract)

Oyster shell is alkaline with pH 9.8, porous, and has high concentration of CaCO3 (up to ca. 95%). It could be used as an alternative of lime fertilizer to immobilize cadmium (Cd) in heavy metal contaminated arable soil. Therefore, this study has been conducted to improve agricultural utilization of oyster shell as an alternative of lime fertilizer that immobilize Cd in heavy metal contaminated arable soil. To do this, we compared effects of calcium (Ca) materials [Ca(OH)2 and oyster shell] on Cd extractability in upland soil and determined mechanisms of Cd immobilization with both Ca materials. Both Ca materials were added at the rates of 0, 0,1, 0.2, 0.4 and 0.8% (wt Ca wt-1) in Cd contaminated upland soil that contained total 6.5 mg Cd kg-1, and the mixtures of soil and Ca material were incubated at 25℃ for 4 weeks. Both Ca materials increased pH and net negative charge with increasing Ca addition and decreased 1 N NH4OAc extractable Cd concentration. 0.1 N HCl extractable Cd concentration markedly decreased with addition of oyster shell but not with Ca(OH)2. 1 N NH4OAc extractable Cd concentration was significantly related with pH and net negative charge of soil. However, there were no significant relationships between 0.1 N HCl extractable Cd concentration and pH and net negative charge of soil. From the above results, Cd immobilization with Ca(OH)2 was mainly attributed to Cd adsorption resulted from increase in pH-induced negative charge of soil. Scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) analyses were conducted to determine mechanism of Cd immobilization with oyster shell. There was no visible precipitation on surface of both Ca materials. However, Cd was dected in innerlayer of oyster shell by EDS analyses but not in that of Ca(OH)2. Therefore, we concluded that Cd immobilzation with oyster shell was different from that with Ca(OH)2 implying Cd immboilization with oyster shell might be due to precipitation of Cd or other chemical reactions in innerlayer of oyster shell. Further study should be conducted to elucidate the mechanism of Cd immobilization with oyster shell.