A PRELIMINARY STUDY OF LEAD AND ARSENIC IN PHILADELPHIA SOILS

Land use in Philadelphia is extremely diverse, both currently and historically, and includes transportation, industrial, commercial, parks and residential areas. This urban tapestry of historical and current land use creates the potential for human exposure to heavy-metals in contaminated dust or bio-concentration in food crops. In order to evaluate this potential public health hazard, we have begun to analyze open spaces in Philadelphia in order to define protocols and best practices for current parks and future sustainable garden sites. We have obtained soil samples from selected areas of the city and analyzed lead and arsenic concentrations with a Thermo Niton X-Ray Fluorescence XL3t Analyzer. Most areas selected for this preliminary study are from largely undisturbed forested land in Philadelphia’s Fairmount Park (the largest inner-city park in the U.S.) and urban recreation centers. At each location a bulk sample was taken at various geomorphic positions or, if little to no topographic change was present at a specific site, then samples were taken systematically at specific intervals from permanent structures.

In initial results, Pb and As concentrations in largely undisturbed park soils range from 17 to 1550 ppm and <10 to 60 ppm, respectively. However, in soils from a former orchard, Pb and As concentrations are as high as 1.8% and 500 ppm, respectively, and are positively correlated. Median measured values in largely undisturbed soils are ca. 230 and 22 ppm, respectively. Concentrations are approximately log-normally distributed. Pb concentrations in the largely undisturbed soils are generally less than those found in previous soil studies in Philadelphia. Initial results suggest a possible topographic control on the distribution of Pb and As as well as multiple Pb/As sources. These data should allow better land use decisions by informed Philadelphia citizens.