Changes in Phytoavailability of Cadmium, Copper, Lead, and Zinc after Application with Eggshell in Contaminated Agricultural Soil

초록

Agricultural soils surrounding mine areas in South Korea are often contaminated with multiple metals such as Cd,Pb and Zn. It poses potential risks to plants, soil organisms, groundwater, and eventually human health. The aimof this study was to examine the changes in phytoavailability of Cd, Cu, Pb and Zn after application with calcinedeggshell (CES; 0, 1, 3, and 5% W/W) in an agricultural soil contaminated by mine tailings. The contents of Cd,Cu, Pb and Zn in soils were 8.79, 65.4, 1602, and 692 mg kg-1 (aqua regia dissolution), respectively. Theexperiments were conducted with lettuce (Lactuca sativa L. var. longifolia) grown under greenhouse conditionsduring a 30-d period. NH4NO3 solution was used to examine the mobile fraction of these metals in soil. Theapplication of CES dramatically increased soil pH and inorganic carbon content in soil due to CaO and CaCO3 ofCES. The increased soil pH decreased the mobile fraction of Cd, Pb, Zn: from 3.49 to < 0.01 mg kg-1 for Cd, from79.4 to 1.75 mg kg-1 for Pb, and from 29.6 to 1.13 mg kg-1 for Zn with increasing treatment of CES from 0 to 5%. In contrast, the mobile fraction of Cu was increased from 0.05 to 3.08 mg kg-1, probably due to the formation ofsoluble CuCO30 and Cu-organic complex. This changes in the mobile fraction resulted in a diminished uptake ofCd, Pb and Zn by lettuce and an increased uptake of Cu: from 4.19 to < 0.001 mg kg-1 dry weight (DW) for Cd,from 0.78 to < 0.001 mg kg-1 DW for Pb, and from 133 to 50.0 mg kg-1 DW for Zn and conversely, from 3.79 upto 8.21 kg-1 DW for Cu. The increased contents of Cu in lettuce shoots did not exceed the toxic level of > 25 mgkg-1 DW. The mobile contents of these metals in soils showed a strong relationship with their contents in plantroots and shoots. These results showed that CES effectively reduced the phytoavailability of Cd, Pb, and Zn tolettuce but elevated that of Cu in consequence of the changed binding forms of Cd, Cu, Pb, and Zn in soils. Basedon these conclusions, CES can be used as an effective immobilization agent for Cd, Pb and Zn in contaminatedsoils. However, the CES should be applied in restricted doses due to too high increased pH in soils.

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