PHYTOREMEDIATION OF LEAD CONTAMINATED SOILS USING VETIVER GRASS RESEARCH HIGHLIGHTS Despite considerable national public health efforts to reduce lead (Pb) exposure, Pb poisoning remains the most common environmental health problem affecting the children in the United States and as well world wide. Phytoremediation is emerging as an attractive option for cleanup of Pb paint-contaminated soils in housing facilities built prior to lead ban in paints. The objective of this study was to investigate the use of a high biomass, metal tolerant grass, Vetiveria zizanioides (Vetiver grass), to remediate Pb paint-contaminated residential soils of variable physico-chemical properties. Developing a successful phytoremediation model requires a good understanding of the role of soil properties governing Pb availability for plant uptake, biochemical mechanisms involved in Pb tolerance, and changes in Pb bioaccessibility. Therefore, a comprehensive greenhouse-based study was conducted to evaluate the effectiveness of vetiver in Pb uptake and reducing soil Pb concentrations. Chelation of Pb is an important factor in enhancing its solubility and therefore availability to vetiver grass in promoting phytoremediation. We compared the effects of two chelating agents – namely ethylenediaminetetracetic acid (EDTA) and ethylenediaminedisuccinic acid (EDDS) – at 4 different concentrations such as 0, 5, 10 and 15 mmol kg-1 soils. Our studies indicate that (A) soil properties determine the extent of soluble Pb (1,2,3); (B) EDTA is more effective than EDDS in mobilizing bound soil Pb (4); (C) unlike EDTA, EDDS reduced the leachable Pb fraction in soils (5); (D) activities of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase were elevated in vetiver under Pb stress (6); (E) lead-binding phytochelatins were induced as a Pb tolerance mechanism (7,8,9); and (F) Pb bioaccessibility in soils decreased with an increase in Pb uptake by vetiver (10). This study demonstrated that EDDS could be regarded as a good chelant candidate for the environmentally safe phytoextraction of Pb using vetiver grass in Pb paint-contaminated residential soils. REFERENCES

1. Andra, SS; Sarkar, D; Datta, R; Saminathan, S. 2006. Lead in soils in paint contaminated residential sites at San Antonio, Texas, and Baltimore, Maryland. BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 77 (5): 643-650.

http://www.springerlink.com/content/3701l8312806j083/ 2. Andra, SS; Sarkar, D; Saminathan, SKM; Datta, R. 2011. Predicting potentially plant-available lead in

contaminated residential sites. ENVIRONMENTAL MONITORING AND ASSESSMENT 175 (1-4): 661-676. http://www.springerlink.com/content/e15l17183254l421/

3. Andra, SS; Sarkar, D; Saminathan, SKM; Datta, R. 2011. Exchangeable lead from prediction models relates to vetiver lead uptake in different soil types. ENVIRONMENTAL MONITORING AND ASSESSMENT. Online First. http://www.springerlink.com/content/71301400w0220718/

4. Sarkar, D; Andra, SS; Saminathan, SKM; Datta, R. 2008. Chelant-aided enhancement of lead mobilization in residential soils. ENVIRONMENTAL POLLUTION 156 (3): 1139-1148.

http://www.ncbi.nlm.nih.gov/pubmed/18479792 5. Andra, SS; Sarkar, D; Saminathan, SKM; Datta, R. 2010. Chelant-assisted Phytostabilization of Paint-

contaminated Residential Sites. CLEAN-SOIL AIR WATER 38 (9): 803-811. http://onlinelibrary.wiley.com/doi/10.1002/clen.200900218/abstract 6. Andra, SS; Datta, R; Reddy, R; Saminathan, SKM; Sarkar, D. 2011. Antioxidant Enzymes Response in Vetiver

Grass:A Greenhouse Study for Chelant-Assisted Phytoremediation of Lead-Contaminated Residential Soils. CLEAN-SOIL AIR WATER. Online First.

http://onlinelibrary.wiley.com/doi/10.1002/clen.201000323/abstract 7. Andra, SS; Datta, R; Sarkar, D; Makris, KC; Mullens, CP; Sahi, SV; Bach, SBH. 2009. Induction of Lead-

Binding Phytochelatins in Vetiver Grass [Vetiveria zizanioides (L.)]. JOURNAL OF ENVIRONMENTAL QUALITY 38 (3): 868-877. http://www.ncbi.nlm.nih.gov/pubmed/19329675

8. Andra, SS; Datta, R; Sarkar, D; Saminathan, SKM; Mullens, CP; Bach, SBH. 2009. Analysis of phytochelatin complexes in the lead tolerant vetiver grass [Vetiveria zizanioides (L.)] using liquid chromatography and mass spectrometry. ENVIRONMENTAL POLLUTION 157 (7): 2173-2183.

http://www.ncbi.nlm.nih.gov/pubmed/19282075 9. Andra, SS; Datta, R; Sarkar, D; Makris, KC; Mullens, CP; Sahi, SV; Bach, SBH. 2010. Synthesis of

phytochelatins in vetiver grass upon lead exposure in the presence of phosphorus. PLANT AND SOIL 326 (1-2): 171-185, Special Issue. http://www.springerlink.com/content/dw05876264354421/

10. Saminathan, SKM; Sarkar, D; Andra, SS; Datta, R. 2010. Lead fractionation and bioaccessibility in contaminated soils with variable chemical properties. CHEMICAL SPECIATION AND BIOAVAILABILITY 22 (4): 215-225.

http://www.ingentaconnect.com/content/stl/csb/2010/00000022/00000004/art00001