Syam S. Andra 1 Rupali Datta 2 Ramana Reddy 2 Sumathi K. M. Saminathan 1 Dibyendu Sarkar 3 1 Environmental Geochemistry Laboratory, University of Texas at San Antonio, San Antonio, TX, USA 2 Biological Sciences, Michigan Technological University, Houghton, MI, USA 3 Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ, USA Research Article Antioxidant Enzymes Response in Vetiver Grass: A Greenhouse Study for Chelant-Assisted Phytoremediation of Lead-Contaminated Residential Soils In a previous study we have demonstrated the suitability of using vetiver grass (Vetiveria zizanioides L.) for the phytostabilization of lead-based paint contaminated residential soils. Vetiver did not show any growth retardation or toxicity symptoms despite high soil Pb levels. Antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) reportedly allow plants to combat metal stress. Thus, we hypothesized that in vetiver, these antioxidant enzymes can play an important role in combating Pb induced stress, and that chelant-bound Pb is less toxic to vetiver com- pared to free Pb in soil. The response of antioxidant enzymes was studied in vetiver grass grown in Pb paint-contaminated residential soils collected from San Antonio, Texas and Baltimore, Maryland. Chelating agents such as ethylenediaminetetraacetic acid (EDTA) and ethylenediaminedisuccinic acid (EDDS) were used to mobilize Pb from bound fractions to the labile pool, facilitating Pb uptake by vetiver. Although the Pb concentration in vetiver from these treatments was significantly higher than those grown in the absence of a chelant, the antioxidant enzymes activities were lower compared to the latter. Antioxidant enzymes activity of vetiver plants grown in the presence of chelants is lower compared to those in without chelant treatment, while they tended to increase with dose in treatments with varying chelant concentrations. Data obtained support the proposed hypothesis. Keywords: Catalase; Chelating agents; Glutathione peroxidase; Phytoremediation; Superoxide dismutase Received: August 22, 2010; revised: February 19, 2011; accepted: February 21, 2011 DOI: 10.1002/clen.201000323 1 Introduction A previous study has presented the potential of phytoremediation to treat lead paint contaminated residential soils and proposed the vetiver grass, Vetiveria zizanioides L., for lead phytostabilization [1]. In brief, lead is a toxic metal that can be harmful to humans, particu- larly children under the age of six, when ingested or inhaled. Lead poisoning has a number of adverse human health effects, but is particularly detrimental to the neurological development of chil- dren [2], contributes to breast cancer in women [3], and interferes with heme biosynthesis and the central nervous system [4]. Lead in paints is the principal source of human exposure to environmental lead in the USA. In 1977, a maximum allowable limit of lead content in paint has been set at 0.06% [2]. However, a significant number of housing facilities built prior to the implementation of this policy still exist [2]. Several investigations have found that natural and anthropogenic factors – such as weathering, chipping, scraping, sanding, and sand blasting of painted pre-1978 structures – induce human exposure to lead via soils or house dust, by airborne routes or tracking of exterior soils into the home [2, 5]. Children living in these houses are at the greatest risk of exposure, as crawling on the ground and playing in backyards can result in ingestion and inhalation of soil- and dust-borne lead [6–8]. Soil lead cleanup is traditionally done via soil removal for off-site disposal, which is expensive and environmentally unsafe, and there- fore not the best approach for cleaning up residential properties. As a result, in situ remediation techniques, such as chemical and biological methods, have become popular in recent years. Phytoremediation has emerged as an attractive option for cleanup of contaminated soils in the pre-1978 housing facilities [1, 9]. The technique is environment friendly, inexpensive, and visually unob- trusive. A high biomass perennial grass, vetiver, can be used for the phytoremediation of soils contaminated with metals [1, 10]. In a hydroponic setup, vetiver can accumulate up to 19 800  2400 and 3350  66 mg Pb/kg dry weight in root and shoot tissues, respec- tively, with no phytotoxic symptoms like growth retardation and chlorosis [11]. However, under natural soil conditions majority of the lead is strongly bound to soil minerals and organic matter [12–14] and is not available for plant uptake. Hence, it is essential to Correspondence: Dr. R. Datta, Department of Biological Sciences, Michigan Technological University, Houghton, MI 49931, USA E-mail: rupdatta@mtu.edu Abbreviation: CAT, catalase; EDTA, ethylenediaminetetraacetic acid; EDDS, ethylenediaminedisuccinic acid; SOD, superoxide dismutase. 428 Clean – Soil, Air, Water 2011, 39 (5), 428–436 ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com