PARENT SESSION
09 - Appraising and Quantifying Bioavailable Pollutant Fractions
2:10 PM to 5:20 PM, Monday, 13 May 2002
Session Chair: Sager, Manfred ¹, Chon, Hyo-Taek ², ^{1 2} .
Stolz B

(09-04) The Chelating Agent Effect for Phytoremediation in the Cd and Pb Contaminated Soil by Lettuce.

LEE, So-Young^*,1, CHON, Hyo-Taek¹, Sager, Manfred², ¹ School of Civil, Urban and Geosystem Engineering College of Engineering, Seoul National University, Seoul, Korea² Federal Office and Research Center for Africulture, Vienna, Austria

ABSTRACT- For the effective phytoremediation some factors such as plant species and bioavailability of heavy metals (Cd and Pb) must be considered. Although good hyperaccumulator plant is grown in the contaminated soils, the plant cannot uptake the metals if the metals are strongly adsorbed to the soil surface. The purpose of this study is to make metals into mobile fraction by using suitable chelating agents and to investigate their uptake potential by lettuce in pot experiments. Lettuce (Lactuca Sativa L.), which is popular as good accumulator of Cd and Pb was used as a target plant. The heavily contaminated soils with Cd and Pb were collected from the Shiheung Cu-Pb-Zn abandoned mine site in Korea. EDTA and NTA were used as synthetic chelating agents and Citric and Malic acids were selected as natural chelating agents. The plants were harvested 5, 10 and 15 days later for the analysis of Cd and Pb. The total concentrations of Cd and Pb in soil decreased with time. The decreasing content from the initial concentration was followed in this order: EDTA(21.9%) >Citric acid(19.0%)> NTA(14.0%)> Malic acid(11.3%) for Cd and EDTA(18.1%)> NTA(8.7%)> Citric acid(7.3%)> Malic acid(6.0%) for Pb. EDTA was the most effective chelating agent for both elements. The differences in the mobile fraction may explain why the extraction of Cd was higher than that of Pb. The average mobile fraction of Cd was 15% of total concentration. In case of Pb, only 0.22% of total concentration remained as mobile fraction. With EDTA, the mobile fraction can be increased from 15% to 30% of total concentration in Cd and from 0.2% to 0.89% in Pb. The phytoremediation coefficient (PC), which means the metal concentration in plant over the metal concentration in soil can also evaluate the efficiency of chelating agents. The PC value for Cd was in the order: EDTA(1.84)> Citric acid(0.89)> Malic acid(0.82). The same order, however the lower value was detected in Pb: EDTA(0.030)> Citric acid(0.021)> Malic acid(0.018).

Key words: Phytoremediation, Heavy metals (Pb and Cd), Chelating agent, Lettuce