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Philadelphia and Delaware Lead Contamination is Associated with Decreased Bacillota Species in Soil of Public Parks in Philadelphia

JSHS · 2025

Rishi Amaravadi, Marilyn Howarth · Friends’ Central School, Wynnewood, PA

Overview

Pennsylvania, Center of Excellence in Environmental Toxicology; Madeleine Sleeman, University of Pennsylvania, Department of Microbiology Background: Lead remains a persistent environmental contaminant despite being banned in consumer products. This study examines lead soil contamination in Philadelphia’s public parks, examining the impact of lead smelters, vehicle emissions, lead paint, and industrial sources on modern-day soil lead levels and microbiome diversity. Hypothesis: Public parks near historical lead smelting and roadways will have significantly higher lead concentrations and altered microbiomes than distant control sites. Methods: Soil samples were collected from three Philadelphia parks at varying distances of historic lead smelting sites and adjacent roadways: Chew Playground (CP), Richmond & Westmoreland Streets (RS), and Vernon Park (VP). 23 soil samples were analyzed f or lead via X-ray fluorescence spectroscopy. DNA sequencing of 16S rRNA genes characterized microbial communities, with a microbiome analysis using Epi2me and Phyloseq. Results: Lead concentrations ranged from 150-700 ppm in RS and VP, exceeding EPA thresholds for children’s play areas, while CP had little detectable lead. Principal Component Analysis revealed distinct microbial compositions at RS and VP compared to CP.. Lead-contaminated sites showed depleted Bacillota (12% ± 6% vs. 33% ± 9%; P=0.0002), known for lead remediation. Conclusion: There was no strong correlation between lead concentrations and distances to the smelting site. However, two out of three sampling sites were found to have higher levels of lead than the EPA threshold. We determined that high lead is associated with a decrease in Bacillota, a phylum that is consistently used to remediate lead in soil. Further sampling is warranted to support bioremediation with Bacillota.

Competition history

  • JSHS 2025 Category not listed

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