토양칼럼반응조에서 Pb 오염토양(1,200 mg/kg)에 강아지풀로 식물상복원공법을 적용하였을 때 EDTA 혹은 인용출미생물(Phosphate solubilizing microorganism) 주입이 식물의 Pb 섭취 및 연직이동에 주는 영향을 연구하였다. EDTA 주입량은 Pb 오염총량과 동일한 mol수이었으며, 6회에 걸쳐 분할 주입하는 방법과 1회에 일괄적으로 처리하는 2가지 방법을 적용하였다. 그 결과 뿌리에 축적된 Pb의 농도는 control(164.7 mg/kg)에 비하여 PSM 처리구(M)는 2.6배, EDTA 분할처리구(ES)는 3.0배, EDTA 일괄처리구(E)는 3.3배가 증가하였고, 줄기에서는 control(8.1 mg/kg)에 비하여 M 처리구는 27배, ES 처리구는 37배, E 처리구 40배가 증가하였다. 뿌리로부터 지상부로 이동한 납의 비율은 control에서 0.06이지만, E 및 ES 처리구는 0.6, M 처리구는 0.5로 큰 차이가 없었다. Pb 제거량은 E 처리구가 많았고, EDTA의 연직이동은 ES 처리구에서 큰 것으로 나타나, 식물수확기 전에 EDTA를 일괄주입하는 방안이 효율적인 것으로 판명되었다. PSM 처리는 EDTA보다 Pb 제거량은 낮았지만 Pb의 식물섭취가 증가하였고, 식물의 성장 및 토양 내 미생물 활성도를 증진하는 장점이 있어 유독한 EDTA를 대체할 수 있을 것으로 판단된다.
Enhanced phytoremediation with EDTA or PSM(Phosphate solubilizing microorganism) was studied using green foxtail (Setaria viridis) in columns packed with 1,200 mgPb/kg contaminated soil to investigate the effects of EDTA or PSM on the plant uptake and vertical migration of Pb. EDTA, equimolar amount of total Pb in the column soil, was administered in two methods: the one was treated with 1/6 aliquots of the equimolar EDTA every week for 6 weeks and the other was treated with single dose of the equimolar EDTA before 14 days of harvest. The results showed that higher concentrations of Pb accumulated in the biomass of green fowtail after the chemical or biological treatment. The plant-root Pb concentration in PSM treatment(M), EDTA aliquot treatment(ES), and single dose treatment(E) was 2.6, 3.0, and 3.3 times higher, respectively, than that in the plant-root of control(164.7 mg/kg). The plant-stem Pb concentration in the M, ES and E treatment was 27, 37, and 40 times higher than that in the stem of control(8.1 mg/kg). The translocation factor, the ratio of shoot/root Pb concentration, was 0.6 in the two EDTA treatment, 0.5 in the M treatment, and 0.05 in the control, respectively. The largest amount of Pb was phyto-extracted in the E treatment whereas vertical migration of EDTA was significant in the ES treatment. This result showed that a single large dose of EDTA before harvest serves better for enhanced phytoremediation of Pb. Although, treatment with PSM showed less Pb phytoextraction by the plant but enhanced both the growth of plants in the column and microbial dehydrogenase activity in the soils. Therefore, enhanced phytoextraction of Pb with PSM treatment can be an alternative option for EDTA treatment, which is toxic to plants and soil ecosystem.
