식물을 이용한 중금속 오염 토양 정화에 있어서 킬레이트제의 적용이 정화효율과 토양생태계에 미치는 영향

Abstract

The phytoextraction has often been proposed as a promising technology to remediation heavy metal contaminated soil. The application of chelates has shown positive effects in increasing the plant available metals in soil. The use of chelates in phytoextraction may not be appropriate due to its high environmetal persistence and toxicity. In this study, the effect of EDTA, EDDS, HA on the uptake of Cd, Ni, Zn, Pb and Cu by the plants(Brassica juncea, Brassica campestris, Sorghum bicolor, Helianthus annuus)were investigated. Mobilization in soil and the toxicity effects by chelates additions on plants and soil ecosystem are also investigated. Addition of EDTA and EDDS generally increases the extractability of the soluble and exchangeable forms of metals. Especially, addition of EDTA increases the exchangeable forms of Pb, Zn, Cu and especially, addition of EDDS increases extractability of the soluble forms of Cd, Ni. Similarly, plant available metals was also. Addition of HA generally reduces the extractability of the soluble and exchangeable forms of metals. However, plant available metals that of extracted at EDTA and EDDS treated soil were generally higher than HA treated soil. This might be attributed to the formation of metal-chelates complex, which ensured a temporary bioavailability of metal. In the heavy metal contaminated soil, heavy metal accumulation in the plant roots increased with EDTA and EDDS addition. Concentrations of metal in shoots were also higher in the plants treated with EDTA and EDDS than those treated with HA. Regardless of the metal type a high accumulation of heavy metals in B.juncea was observed. Despite the high biomass production of H.annuus, metal concentration in roots was the lowest. The application of chelates did not increase the S/R ratios at heavy metals in plants used in the study. It was observed from the results than EDTA and EDDS treated soil reduced the net shoots and roots biomass production of the plants, except for S.bicolor and H.annuus. The results suggest that soil amendments with chelates may accelerate the phytoextraction of heavy metals from contaminated soil, while EDTA additions inhibitated the dehydrogenase activity and the indigenous microorganisms. Moreover, severe chlorosis, with more yellowish green leaves, was observed in EDTA and EDDS treated plants. To choose proper chelates and plants for removal of heavy metals using phytoremediation, chelate effects on heavy metal fate in soil, inhibition of plant growth, degree of stimulation of metal uptake by plant, and toxic effects soil ecosystem should be considered.