Wednesday, November 7, 2007 - 12:00 PM
326-7

Effects Phosphate Rock and Iron-Oxide on Immobilization of Lead and Arsenic in Florida Shooting Range Soils.

Uttam Saha, Abioye Fayiga, Autumn Wang, Lena Q. Ma, and Xinde Cao. University of Florida, Soil and Water Science Department, University of Florida, Soil & Water Science Department, Gainesville, FL 32611

Lead pollution in shooting range soils is of environmental concern due to the adverse impacts of Pb on human and animals. The objective of this study was to evaluate the effectiveness of P and Fe-oxide in simultaneously immobilizing Pb and As in 6 shooting range soils. The total soil Pb concentrations (by USEPA Method 3050B) ranged from 1,538 mg/kg in a pistol range to as high as 70,350 mg/kg in a rifle range. Total As ranged from 0.9 to 257 mg/kg. Laboratory studies evaluated the efficacy of P-based amendments (P/Pb molar ratio of 4:1) with and without iron-oxide (at Fe/As molar ratios of 20:1 and 100:1) treatments. The results showed that TCLP-Pb concentrations in the soils were reduced from 19-2422 to 1.75-5.16 mg/L and SPLP-Pb from 1-3.8 to to 0.2-3.0 mg/L in P-treated soils. Addition of Fe oxides significantly reduced TCLP-As from 15-41 to 6-8 mg/L. X-ray diffraction revealed the soil contained predominantly cerussite (PbCO3), which is soluble during TCLP extraction. Lead-phosphate was formed in P-treated soils, which is resistant to TCLP extraction. A kinetic study by mixing a berm soil and phosphate rock showed formation of Pb-phosphate during TCLP extraction. The research findings are important for properly managing the Pb and As risk associated with shooting ranges.