THE GOAL OF SUSTAINABLE URBAN GARDENING WITH THE CHALLENGE OF LEAD CONTAMINATED SOIL

Lead contamination is a serious public health issue that is compounded when urban gardening is an integral part of community life and food security. Our lab has formed a partnership with The Food Project, a community organization that promotes sustainable and organic agriculture in Roxbury, MA. We have used field portable x-ray florescence (FP-XRF) to test over 500 soil samples and have found that 90% of samples contain concentrations of lead greater than the MA Department of Environmental Protection (MA-DEP) reportable level of 300 µg/g lead in soil. The principle goals of our research are to: 1) characterize the spatial variability of the lead at the neighborhood scale, 2) fingerprint the sources of lead in the gardens, 3) assess the chemical speciation and bioavailability of lead and 4) devise and test a phytoremediation scheme. Since The Food Project is committed to organic gardening, we are testing crops for phytoremediation, such as sunflowers, mustards, and collards that are both commonly grown in the neighborhood and documented heavy metal hyperaccumulators. We are using textural-analytical approaches (scanning electron microscopy with energy dispersive spectroscopy) coupled with trace element ratio analysis (polarized energy dispersive x-ray florescence) and lead isotope analysis (inductively coupled plasma mass spectroscopy) to evaluate the mass balance and geochemical characteristics of the lead found in garden soils. Preliminary results indicate that lead concentrations are highest in the finest particle size of soil and that lead is often associated with an identifiable suite of trace elements. Initial observations suggest that point and non point sources, lead-based paint chips and particulate matter from leaded gasoline, are contributing the overall soil lead burden. A detailed geochemical assessment of lead in urban garden soils will provide insight into the severity of lead contamination in this high exposure setting and help to design a framework for further research and successful remediation schemes.