Trace Element Soil Contamination at Urban Community Gardens in Washington, DC

In recent years, urban gardening has become a popular form of environmental, food, and social justice. Urban community gardens such as those in Washington, DC can reduce the environmental footprint of food production, provide access to healthy produce in “food deserts,” and provide other social, educational, and even financial benefits. However, the rising popularity of urban gardening has put many people in close contact with urban soils, which are likely to contain various contaminants due to concentrated human activity over extended periods of time. This study investigates heavy metal soil contaminants found in community gardens located in Washington, DC. 45 soil samples taken from various locations and depths at 13 community gardens across Washington, DC were analyzed for trace element content using x-ray fluorescence (XRF). While most of the soil samples analyzed fell below US EPA action levels for common contaminants such as lead, cadmium, cobalt, copper, and zinc, some samples showed concentrations high enough to merit some concern. High concentrations of Pb (above the US EPA action level of 400 ppm), which can cause serious health problems in children, was found in the native soil of three garden sites. The bioavailability of Pb and risk of danger to humans depends on many factors which will be explored in this paper. Because of the potential for direct exposure and ingestion of contaminated soil, this study also reviews potential measures to avoid contamination when gardening on urban soils in Washington, DC to ensure the safety of these valuable social, nutritional, and environmental resources