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Updated: May 5, 2026

Chemical Gardens as Flow-through Reactors Simulating Natural Hydrothermal Systems
Published on: November 18, 2015
Metals in downtown Washington, DC gardens.
J R Preer1, J O Akintoye, M L Martin
1Environmental Science Department and Agricultural Experiment Station, University of the District of Columbia, 20008, Washington, DC.
Downtown Washington, DC gardens show high soil lead (Pb) levels, exceeding city-wide averages. Leaf vegetables also had elevated lead, likely from lead-based paint contamination.
Area of Science:
- Environmental Science
- Urban Ecology
- Soil Science
Background:
- Urban soils can accumulate heavy metals from various anthropogenic sources.
- Lead (Pb) contamination in urban gardens is a public health concern, potentially affecting food safety.
Purpose of the Study:
- To assess heavy metal concentrations, specifically lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn), in urban garden soils and leaf vegetables.
- To compare metal levels in a dense urban area with city-wide data and identify potential sources.
Main Methods:
- Analysis of soil samples from 95 gardens and leaf vegetables from 33 gardens in downtown Washington, DC.
- Inductively coupled plasma mass spectrometry (ICP-MS) or similar techniques for heavy metal quantification.
- Spatial analysis to determine metal distribution relative to housing structures.
Main Results:
- Mean soil lead (Pb) concentration was 680 μg/g, significantly higher than city-wide averages.
- 46% of soil samples exceeded 500 μg/g Pb, and 17% exceeded 1000 μg/g Pb.
- Elevated Pb, Zn, and Cd levels were observed closer to houses, suggesting lead-based paint as a likely source.
Conclusions:
- Downtown DC garden soils exhibit high lead contamination, posing potential risks.
- Lead-based paint is a probable source of soil lead contamination in these urban gardens.
- Leaf vegetables grown in these gardens showed elevated lead levels, indicating potential dietary exposure pathways.
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