Role of Chelating Agents in Enhancing Lead Uptake by Vetiver Grass (Vetiveria zizanioides L.) from Lead-BasedPaint Contaminated Residential Soils.
Sumathi KPM Saminathan, Dibyendu Sarkar, Rupali Datta, and Syamsundar Andra. Univ of Texas, San Antonio, 6900 N Loop 1604 W, San Antonio, TX 78256
Lead based-paint is the most significant source of lead (Pb) exposure among children in U.S. Our preliminary results using soils collected from ten houses each in San Antonio, TX and Baltimore, MD showed that these soils were highly contaminated, with Pb concentrations ranging from 36 to 4182 mg kg-1. We hypothesized that phytoextraction of Pb using vetiver grass (Vetiveria zizanioides L.) would eventually reduce total Pb concentrations in the contaminated soils. A greenhouse column experiment is currently in progress to explore the efficiency of vetiver grass in remediating Pb based-paint contaminated residential soils. One soil each from San Antonio (acidic soil) and Baltimore (alkaline soil), having similar Pb concentration was selected and planted with vetiver grass. Sequential extraction of soils at time zero showed that the amount of phytoavailable fraction of Pb was very less in both San Antonio (<1.5% of total) and Baltimore (<0.5% of total) soils. The soils had very high percentage of Pb in Fe-Mn oxide fraction (57% in San Antonio soils; 79% in Baltimore soils), indicating the availability of Pb for plant uptake would be very low. In order to enhance phytoavailable Pb in soil solution and plant uptake, two chelating agents, namely EDTA and EDDS, were added at three different rates (5, 10 and 15 mmol kg-1 of soil) after two months of planting. Plants were harvested after ten days and analyzed for total Pb to determine the decontaminating potential of vetiver grass. The relative effectiveness of EDTA and EDDS in enhancing Pb uptake by vetiver grass was compared with control plants grown in unamended soils.