Field Based Evaluations of Trace Element Transfer from Contaminated Urban Garden Soils to Vegetables

Tens of thousands of brownfields can be found in cities, towns, and rural areas across the United States. Our work has focused, in part, on the conversion of brownfields to garden areas and is motivated by the increasing interest in locally produced foods. Challenges of converting brownfields to community gardening sites will be discussed using three urban–community garden sites located in Kansas City, MO; Tacoma, WA; and Indianapolis, IN, as examples. The Kansas City site had mildly elevated levels of lead (Pb); the Tacoma site had mildly elevated levels of Pb and arsenic (As) and the Indianapolis site had elevated levels of polycyclic aromatic hydrocarbons (PAHs), in addition, to mildly elevated levels of Pb and As. Suitable safety/corrective measures were suggested and implemented after thorough evaluation of soil properties. Measures focused on reducing both direct (soil–human) and indirect (soil–plant–human) exposure of Pb, As, and/or PAHs to the gardeners and their children.  In addition, field test plots were established within the community gardens, and three vegetable crop types with three very different growth and contaminant uptake patterns were planted. Effectiveness of selected site-specific soil amendments to reduce bioavailability of Pb, As, and/or PAHs was evaluated. Different methodologies will be utilized, throughout the project, to understand the significance of potential soil–plant–human exposure pathway of contaminants while gardening on mildly contaminated sites. Efforts were also made to understand relationships between key soil properties and contaminant bioavailability.