농경지 토양에서 패화석에 의한 카드뮴의 용출성 및 부동화 기작 구명

BACKGROUND: Oyster shell(OS) is alkaline with pH 9.8, porous, and has high concentration of CaCO3. 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 compare effects of calcium(Ca) materials [OS and Ca(OH)2] on Cd extractability in contaminated soil and determined mechanisms of Cd immobilization with OS. METHODS AND RESULTS: 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 soil and the mixtures were incubated at 25℃ for 4 weeks. Both Ca materials increased pH and negative charge of soil with increasing Ca addition anddecreased 1N NH4OAc extractable Cd concentration. 0.1 N HCl extractable Cd concentration markedly decreased with addition of OS. 1 N NH4OAc extractable Cd concentration was related with pH and net negative charge of soil, but not with 0.1 N HCl extractable Cd concentration. We assumed that 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 OS. There was no visible precipitation on surface of both Ca materials. However, Cd was detected in innerlayer of OS by EDS analyses but not in that of Ca(OH)2. CONCLUSION: We concluded that Cd immobilization with OS was different from that with Ca(OH)2. OS might adsorbed interlayer of oyster shell or have other chemical reactions.