USING VETIVER GRASS TO REMOVE LEAD FROM RESIDENTIAL SOILS OF SAN ANTONIO, TEXAS: A SIMULATED FIELD STUDY Rupali Datta 1, Dibyendu Sarkar 2 and Ramesh Attinti 2 1 Biological Sciences, Michigan Technological University, Houghton, MI, 2 Earth and Environmental Studies, Montclair State University, Montclair, NJ

CDC lowered the reference elevated blood lead level (EBLL) for children from 10μg/dL to 5µg/dL in Soil and house dust in pre homes are the principal sources of lead absorption among children. Traditional methods of soil remediation are expensive and unrealistic for residential soils. Lead toxicity

Lead health effects Young children under the age of six are especially vulnerable low levels Reduced IQ Learning disabilities Attention deficit disorders Behavioral problems Stunted growth Impaired hearing Kidney damage high levels Mental retardation Coma, and death Juvenile delinquency and criminal behavior

Pathways of lead in the environment

Lead remediation Traditional method: “Dig and haul” for residential areas Chemical remediation Ingestion/inhalation pathways Phytoremediation Naval Facilities Engineering Service Center, Port Hueneme, CA.

Why phytoremediation? Excavation Phytoremediation 30,000 Tons 1200 Tons 120 Tons Comparative Mass Disposal (10 Acres) Biomass Ash

Candidates for lead phytoremediation Grasses Alfalfa Cabbage Sesbania sp. Vetiver Sunflower Morning glory Red clover Corn Indian mustard

Hyperaccumulators By definition must accumulate at least 100 mg kg-1 (0.01% dry wt.) Cd, As and some other trace metals 1000 mg kg-1 (0.1 dry wt.) Co, Cu, Cr, Ni and Pb and 10,000 mg kg-1 (1% dry wt.) Mn and Zn

Phytoremediation - Vetiver Hyper accumulator Fast growing High biomass Extensive root system Non Invasive Easy to harvest

Vetiver (cont.) Perennial grass (1-2 m tall) Massive complex root system penetrating to deeper layers of the soil (3-4 m deep) Reduces erosion and leaching Survives in many different types of soil and in a wide range of climates Inexpensive, easy to maintain

Phase I: Greenhouse study Lead paint contaminated soil samples were collected from San Antonio, TX from 11 house sites Soil physico-chemical properties were analyzed. A greenhouse study was initiated

Phase I: Soil properties Soil Properties Lead paint contamianted soil samples from house sites pH EC , LOI % WC% Carbonate (%) Clay (%) Silt (%) Sand (%) Pb (Mehlich 3) , Pb (Olsen) Pb (Oxalate) Pb (Total)79.11, ,1334, ,3652,3462,2783,1641,513

Lead-contaminated soil (6”h) Clean Sand (7”h) Plastic mesh PVC column (15”x 6”) PVC cap Leaching tube Marble Vetiver grass Lead-contaminated soil (6”h) Clean Sand (7”h) Plastic mesh PVC column (15”x 6”) PVC cap Leaching tube Marble Vetiver grass Soil Property pH8.07 ± 0.1 EC189.1 ± 4.3 SOM (%)2.70 ± 0.2 CO 3 2- (%)48.2 ± 4.4 Clay (%)54.2 ± 7.6 Silt (%)29.7 ± 3.5 Sand (%)16.1 ± 2.1 Elemental Composition (mg/Kg soil) Phosphorus1,056 ± 69 Calcium59,428 ± 4532 Magnesium3,278 ± 468 Iron14,225 ± 2691 Aluminum14,269 ± 1648 Lead1,513 ± 312 Chelants: 1) Ethylenediaminetetraacetic acid (EDTA) 2) [S,S ’ ]ethylenediaminedisuccinic acid (EDDS) Chelant Concentrations: EDTA and EDDS (0,5, 10, and 15 mM/ Kg soil) Experimental Duration: 70 days (Chelant addition to the soils at the end of 2nd month) Experimental design

Lead uptake by vetiver A B C D a b c d A B C D a b c d

Lead concentrations in soil

Conclusions: Phase I study Vetiver grass is a lead accumulator, and is effective in remediating lead-contaminated soils, in conjunction with chelating agents. Lead accumulation increased with increasing concentration of chelating agents, EDTA and EDDS. EDTA was more effective in increasing lead accumulation in vetiver compared to EDDS. Application of chelating agents significantly increased root to shoot translocation of lead on vetiver. Between 14-20% reduction in total soil lead was observed at the end of the study.

Phase II: Simulated field study Lead paint contaminated soil samples were collected from San Antonio, TX from 9 house sites Soil physico-chemical properties were analyzed. A simulated field study was set up in San Antonio

Phase II: Simulated field study Soil Name pH Total Pb concentration (mg/kg) Sutton Dr7.64 ± ± 3.67 Edison Dr7.38 ± ± 2.84 W. Craig Pl7.37± ± Delmar7.41 ± ± Barrett Pl7.64 ± ± Brighton7.96 ± ± Ware Blvd7.24 ± ± Bailey Ave7.50 ± ± Hackberry Ave7.62± ± All data are shown as mean (n=3) ± standard deviation

Experimental design Wooden platforms (4’ x 3’ × I’) 5 inches of play sand 5 inches of contaminated soil 2 platforms from each site Vetiver grass Fescue grass No plant control Plants were grown for 3 months 10 mmol/kg EDDS was applied Soil, plant and leachate sample were collected before and 15 d after EDDS application and analyzed for lead.

Vetiver and fescue grass platforms

EDDS application

Soil Erosion from Platforms S. NoSoilErosion (Kg) 1 Vetiver platformBailey0.05 Craig Hackberry Fescue grass platformCraig Bailey Hackberry Control (no plant) platform 0.62

Plant uptake: EDDS application

Plant uptake: EDTA application

Effect of lead on grasses

Percent removal after five cycles

Lead leaching from compost S. NoSoil name Pb in Vetiver Compost (mg/L) Pb in Fescue grass Compost (mg/L) 1Bailey0.85 ± ± W. Craig0.69 ± ± Hackberry1.14 ± ± 0.03

Conclusions: Phase II study Vetiver grass performed well during Phase II, and showed no phytotoxic symptoms. Yellowing and growth inhibition was seen in control fescue grass. Compared to fescue grass, vetiver accumulated times higher concentration of lead. After five cycles of chelating agent application, between 18-22% of the soil lead was reduced. The concentration of lead in the decomposed clippings from vetiver and fescue grass were significantly lower than the USEPA TCLP limit of 5 mg/L for lead. Hence, grass clippings can be safely disposed as non-hazardous waste.

Lead technical studies program of Housing and Urban Development Acknowledgement