Pilot study of a community-engaged phytoremediation garden: Evaluating site-specific efficacy of the mammoth sunflower in soil with elevated lead (Pb) in west Atlanta, GA Público
Borbón Wun, Alicia May-Lin (Spring 2020)
Abstract
Background: Soil Pb levels above Environmental Protection Agency (EPA) screening levels (400 ppm) were recently discovered in the English Avenue neighborhood of west Atlanta. While EPA Region 4 has started excavation, members of urban gardening organization Historic Westside Gardens (HWG) have expressed the desire for a less disruptive and affordable method for remediation. Phytoremediation, using plants to extract contaminants from soil, has been utilized in other sites of legacy contamination and was utilized for this field experiment.
Methods: Three plots were established in the native soil in an empty lot in the English Avenue neighborhood. Mammoth sunflowers were planted in two plots, one with compost and one without, while one plot was left empty. Sunflowers were planted Jun 24 and harvested Sep 21. Soil Pb was measured by X-Ray Fluorescence (XRF) and Inductively Coupled Mass Spectrometry (ICP-MS) before planting, and after harvesting. The seeds of five sunflowers were tested for bioavailability of Pb and arsenic (As). Bioavailable Pb and As levels were measured by ICP-MS following a procedure simulating human stomach and intestine digestion. A risk assessment was conducted using Integrated Exposure Uptake Biokinetic Model (IEUBK) software (EPA Superfund).
Results: Average Pb levels decreased 10 ppm (p=0.612) in the plot without sunflowers, decreased 22 ppm (p=0.097) in the plot with sunflowers without compost, and increased 143 ppm (p<0.0001) in the plot with sunflowers with compost. Levels of Pb and As in sunflower seeds were below FDA regulations for similar food products. The IEUBK model predicted postulated average soil Pb levels would result in 16.7% to 44.7% of the 0-72-month population to have blood Pb levels over 5 µg/dL.
Conclusions: The community-engaged model of this thesis proved highly successful in the formulation of relevant research questions to residents. Results regarding efficacy of the mammoth sunflower are inconclusive. However, important logistical information can be utilized for further field experiments, including the suggestion to use a hyperaccumulator plant with smaller roots given the neighborhood history of buried industrial waste. Results from IEUBK risk assessment indicate the need for expanded blood Pb level testing in children in the English Avenue neighborhood.
Table of Contents
Table of Contents
1. Introduction........................................................................................1
1.1 Childhood Lead Poisoning in the U.S. ..................................................1
1.2 Health Effects of Arsenic ....................................................................2
1.3 English Avenue neighborhood history .................................................2
1.4 Ongoing Community-Engaged Research Partnership ............................3
1.5 Phytoremediation as a potential community-engaged solution .............5
2. Methods .............................................................................................6
2.1 Site Description and Experimental Design ...........................................6
2.2 Plant Materials ..................................................................................8
2.3 Sampling Methods – Soil ....................................................................8
2.4 Sampling Methods – Plants ................................................................8
2.5 Lab Methods - Soil .............................................................................9
2.6 Lab Methods – Seeds .........................................................................10
2.7 Statistical Analysis ............................................................................10
2.8 Population Risk Assessment ...............................................................11
3. Results ................................................................................................12
3.1 Change in Soil Pb ...............................................................................12
3.2 Change in Soil As ...............................................................................15
3.3 Correlation of XRF and ICP-MS Measurements .....................................16
3.4 Bioavailability Results in Sunflower Seeds ............................................17
3.5 Population Risk Calculation ................................................................19
4. Discussion .......................................................................................... 20
4.1 Efficacy of mammoth Sunflowers .........................................................20
4.2 Inter-Measurement Correlation: XRF vs. ICP-MS ..................................22
4.3 Accumulation of Pb and As in Sunflower Seeds .....................................22
4.4 Population Risk ..................................................................................23
4.5 Community-Engaged Approach ...........................................................24
5. Conclusions .........................................................................................25
5.1 Suggestions for Future Use of Phytoremediation ...................................25
5.2 Suggestions for Continued Relationship of Lab Group with Community ..26
References ...............................................................................................28
Appendix A ..............................................................................................28
About this Master's Thesis
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