Sustainable Gardening Initiatives in Previously Used Urban Soils

The objective of the project was to test the soil quality of a community garden in the Southern California urban area. Test plots were established in urban mildly contaminated soils. The plants used for testing (carrots, beets, lettuce and radish) all had different uptake and growing characteristics. They were grown for four cycles with and without site-specific suitable best management practices (BMPs). Compost, lime, and compost +lime were used as treatments to reduce the mobility of lead (Pb) in soil. Soil testing was conducted before and after, gardening and harvesting activities. Produce grown under different treatments was tested for soils lead uptake. Moreover, to assess lead bio-accessibility due to human ingestion of lead-containing soil, soil lead bio-accessibility was measured using physiologically based extraction test (in vitro method). Results showed that the manure treatment did not have a significant effect in the plant uptake of lead. The lead concentrations in the root crops were above 1.5mg/kg. However, the uptake of leafy crops (grown above ground surface) was below 1.5mg/kg. Bio-accessible lead concentrations ranged from about 11.9% (in the control soil and lime treated plots) to 12.8% (in both lime and compost added plots) indicating that bio-accessibility of lead in these soils was lower than 30% bio-accessibility as required by EPA