Sources and Types of Contaminants

Metals are chemical elements that occur naturally in our soils in some places. However, human activities have moved elements like lead around so that some areas have much higher levels than what we would see in an undisturbed area.

Soils are more likely to be contaminated with lead or other metals if they are near an older painted structure, busy roadways, old orchard lands, factories, manufacturing facilities, industry, treated lumber, or other sources. A little bit of detective work to learn about the history of a site and activities nearby can provide clues about whether contaminants may be a concern.

Observing your plants and soil is a good start, but doesn’t always tell the whole story. Plants can grow happily in soils high in lead and some other metals, so it often impossible to tell by looking at a soil whether or not contamination is a concern. Other contaminants can be harmful to plants but not pose human health risks. If you do see any evidence of past burning or chemical spills (stains, odors, etc.) that can be a sign that your soils may have been impacted by these activities.

Key resources include:

  • “Metals in Urban Garden Soils“. Healthy Soils, Healthy Communities fact sheet with information about metals commonly found in urban garden soils, including sources, behavior in garden soil, concerns about human and plant health, what gardeners can do, and related topics. 9pg (PDF), March 2015.
  • “Sources and Impacts of Contaminants in Soils”. Cornell Waste Management Institute fact sheet. 6pg (PDF), April 2009.

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