Phytoremediation of Lead-Contaminated Soil in West Atlanta Public

Abstract

The HERCULES pilot soil project at Emory University has discovered lead (Pb) contamination in residential and garden soils within West Atlanta neighborhoods. Phytoremediation has been shown to be a cost-effective remediation method to remove Pb contamination in soil. However, the plant species with strong potential for phytoremediation of Pb contamination have not been comprehensively investigated in the literature. The goal of this study was to determine the intervention potential of cultivating commonly-used plants to reduce concentration and mobility of Pb in soil. A greenhouse study was conducted to assess the efficacy of four plant species (Helianthus annuus (sunflower), Gomphrena globose (globe amaranth), Brassica pekinensis (Chinese cabbage), and Vigna unguiculata (cowpea)) for the removal and immobilization of Pb in contaminated soil as well as to evaluate the efficiency of EDTA and compost applications as phytoremediation enhancement methods. We used soils with a concentration of 515 ppm (mg/kg) Pb sampled from a residential site in West Atlanta and cultivated plants in the contaminated soil for 60 days. After the harvest, the mean Pb concentrations in four plant species were 23.5, 25.7, 50.0, and 58.1 ppm, respectively, and the root was the major site of Pb accumulation. The ratio of Pb concentrations in the shoot to the root, referred to as translocation factor (TF), was less than 1 for all species, suggesting their potentials for phytostabilization. The highest Pb concentration, TF, and biomass were found in cowpea (V. unguiculate). The soils growing sunflower (H. annuus) were additionally treated with ethylenediaminetetraacetic acid (EDTA) solution (0.1 g/kg) and compost (20% soil blend), respectively. EDTA treatment resulted in a significant increase in the total Pb uptake by sunflowers. Compost treatment increased biomass production and reduced the bioavailability of Pb in soil. We found that: 1) cowpeas (V. unguiculate) were the most favorable for Pb uptake and immobilization compared to the other three species; and 2) the addition of EDTA was shown to improve phytoextraction and the application of compost was shown to enhance phytostabilization.

Table of Contents

I. INTRODUCTION…………………………………………………………………….1

II. LITERATURE REVIEW…………………………………………………………….5

2.1 Phytoextraction vs. Phytostabilization……………………………………..5

2.2 Soil Amendments…………………………………………………………………8

2.3 Translocation Factor and Bioconcentration Factor……………………..11

2.4 Previous Research of Selected Species……………………………………..12

III. MATERIALS AND METHODS………………………………………………….15

3.1 Soil Sampling and Characterization………………………………………...15

3.2 Plant Materials and Pot Experiment………………………………….........16

3.3 Cultivation Practices……………………………………………………..........17

3.4 Post-Phytoremediation Analyses…………………………………....……...18

3.5 Determination of Translocation and Bioconcentration Factor…...…19

3.6 Determination of Total Lead Uptake………………………………........…19

3.7 Statistical Analysis………………………………………………………………20

IV. RESULTS……………………………………………………………………………20

4.1 Lead in Soil…………………………………………………………………....….20

4.2 Biomass Production……………………………………………………....…...20

4.3 Lead Accumulation in Plant Tissues……………………………......….….21

4.4 Translocation Factor and Bioconcentration Factor….…………………22

4.5 Total Lead Uptake…………………………………………………........……..23

4.6 Bioavailability of Lead in Vegetables……………………………......…….24

4.7 Enhanced-Phytoremediation with EDTA and Compost……………….24

V. DISCUSSION………………………………………………………............……..26

VI. CONCLUSION………………………………………………………….......……32

VII. REFERENCES…………………………………………………………......…....33

About this Master's Thesis

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School	Laney Graduate School
Department	Environmental Sciences
Degree	M.S.
Submission	Master's Thesis
Language	English
Research Field	Environmental Sciences Environmental Health
Mot-clé	Phytoremediation Heavy metal soil contamination
Committee Chair / Thesis Advisor	Eri Saikawa, Emory University
Committee Members	Peter Barry Ryan, Emory University Dana Boyd Barr, Emory University

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