Wednesday, 9 November 2005
9

Characterization of Lead-Contaminated Residential Soils: an Appraisal for Phytoremediation.

Syam S. Andra, Rupali Datta, Dibyendu Sarkar, and Hussein Mohamed. Environmental Geochemistry Laboratory, University of Texas at San Antonio, 6900 North Loop 1604 West, San Antonio, TX 78249

Lead (Pb) is a toxic metal that can cause disabilities, mental and behavioral problems, especially in children. Hand-to-mouth activity in lead-contaminated soil/dirt is the number one exposure route used by the USEPA to assess the human health risk associated with Pb ingestion. Deteriorated Pb-based paint from the walls of residential properties is deposited in the surrounding yards, posing a serious health risk for children playing in these yards. Lead-based compounds are persistent in the environment due to their low degradation rates, and, thus, tend to accumulate in the soil. There is a growing need for cost-effective strategies to clean up Pb from Pb-contaminated residential areas, where the majority of the houses were constructed prior to 1978. Phytoremediation is an emerging cost-effective technique that involves the use of plants to remove certain hazardous environmental pollutants. Certain species that are hyperaccumulators clean up contaminated soils by uptake, immobilization, degradation, or transformation within their physiological systems. Effective uptake and detoxification of Pb by plants requires Pb to be in a phyto-available form, which is in turn is governed by the physico-chemical properties of the contaminated soils. The present study focused on determining total and potentially phytoavailable Pb concentrations in Pb-based paint contaminated residential soils, and on assessing the various soil physico-chemical factors that might influence Pb availability to plants. Soils were collected from ten residential sites each in San Antonio (basic soils) and Baltimore (acid soils), which were considered to be at risk because of Pb concentrations higher than the recommended SCL of 400 mg/kg by the USEPA. Potential phytoavailability of soil-Pb was identified to be a function of certain soil chemical properties, soil pH in particular. Future studies will aim to assess the capacity of a Pb-accumulating grass in remediating the Pb-contaminated residential soils.

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