중금속 오염 논토양에서 카드뮴의 부동화와 식물이용성에 대한 석회 시용 효과

Abstract

BACKGROUND: Many studies associated with cadmium (Cd) immobilization using lime fertilizer have been conducted for several decades. However, these studies did not suggest exact mechanism of Cd immobilization using lime fertilizer and evaluated effect of lime fertilizer on Cd phytoavailability in rice paddy soil under field condition. METHODS AND RESULTS: This study was conducted to determine exact mechanism of Cd immobilization using lime fertilizer and evaluate liming effect on Cd uptake of rice in contaminated paddy soil. Ca(OH)2 was mixed with Cd contaminated arable soil at rates corresponding to 0,1,000, 2,000, 4,000, and 8,000 mg/kg. The limed soil was moistened to paddy soil condition, and incubated at 25℃for 4 weeks. NH4OAc extractable Cd concentration in soil decreased significantly with increasing Ca(OH)2 rate, since Ca(OH)2 markedly increased net negative charge of soil by pH increase, and decreased bioavailable Cd fractions (F1;exchangeable + acidic and reducible Cd fraction). Calculated solubility diagram indicated that Cd solubility was controlled by soil-Cd. NH4OAc extractable Cd and F1concentration were negatively related to soil pH and negative charge. Ca(OH)2 was applied at rates 0, 2, 4, and 8Mg/ha and then cultivated rice in the paddy soil under field condition. Cadmium concentrations in grain, straw, and root of rice plant decreased significantly with increasing application rate of Ca(OH)2. CONCLUSION(S): Alleviation of Cd phytoavailability with Ca(OH)2 can be attributed primarily to Cd immobilization due to the increase in soil pH and negative charge rather than precipitation of Cd(OH)2 or CdCO3, and therefore,Ca(OH)2 is effective for reducing Cd phytoavailability of rice in paddy soil.