Monday, November 13, 2006

Phytoremediation of a Lead-Contaminated Urban Community Garden.

Lucas Hathaway and Samantha Langley-Turnbaugh. Univ of Southern Maine, 37 College Ave, Dept of Environmental Science, Gorham, ME 04038

 Recent studies have shown elevated levels of lead in Portland, Maine soils, originating from historic sources including lead paint, construction materials, and gasoline additives. Lead poisoning has been linked to developmental delays and neurotoxic effects in children, and reproductive difficulties in women. This study focused on soil lead levels in a community garden used to provide fresh foods to recent immigrant and low-income residents. The primary goal of our research was to decrease lead concentrations using phytoremediation, and subsequently assess the site’s suitability for growing crops for human consumption. We compared total and plant-available lead levels before and after two seasons’ remediation with spinach (Spinacea oleracea), sunflowers (Helianthus annus), and Indian mustard (Brassica juncea). Laboratory analyses show a current total lead concentration of 189 mg/kg, approximately a 3% reduction achieved by two seasons’ remediation. Current plant-available concentrations are approximately 75 mg/kg, a reduction of 10%.  Spinach was by far the most effective species at taking up lead from the soil, with an average concentration of 195 mg lead/g dry weight.  Current total lead concentration in the soil is below both federal and state advisory levels, but considerably above most international standards and critical limits.  This study also held some valuable lessons about working in the dynamic, relatively uncontrolled “real world” research environment.  Soil testing and remediation efforts had to be reconciled with the community group’s use of the garden.  Research efforts were frustrated and compromised at times by unanticipated disturbance of the site, emphasizing the importance of strong communication and integration of various groups’ interests and efforts.