Trace Metal Concentration and Partitioning Among Vegetable Varieties.

Community gardens have helped provide local and fresh produce but, many residents are unaware of the possible health risks associated with the cultivation of these sites.  One metal that is of concern on contaminated sites is Pb.  Soils may be contaminated with Pb from various sources including flaking lead paint, incinerators, and motor vehicles that use leaded gasoline.  Urban environments where Pb concentrations may range from less than 100 mg/kg to well over 11,000 mg/kg in general have received higher depositions of Pb from vehicular emissions than rural areas.  Approaches to limit the concentration of trace metals in plants grown on contaminated sites include the addition of compost, lime, and phosphorous, but can be expensive and impractical while gardening in an urban environment.  An alternative approach to decrease the transfer of trace metals to produce is varietal selection.  Selecting varieties that for genetic reasons have reduced ability to accumulate and translocate potentially harmful trace metals can be a more practical approach for an urban environment.  In this greenhouse study four lettuce and four carrot varieties were used to determine the accumulation and partitioning of Pb, Cd, and As among all eight varieties with contaminated soil collected from a community garden.  For comparison, the four varieties of each vegetable were grown in soil with the addition of urea and soil with the addition of compost.  Accumulation and partitioning of Pb and As varied by variety while Cd uptake was minimal and no significant difference was observed.  The addition of compost significantly decreased the concentration of Pb and As in vegetables when compared to the vegetable varieties that did not include compost.