Effects of phosphate rock and iron-oxide on immobilization of lead and arsenic in Florida shooting range soils U. Saha, A. Fayiga, A. Wang, L.Q. Ma, and X. Cao Soil and Water Science Department University of Florida

Introduction Pb contamination in shooting range soils is a public health concern worldwide Shooting ranges in the US 9,000 nonmilitary Numerous military 20 million tons of lead bullets fired in the US in the 20th century Lead bullets a 10-y old, 4-5 acre range 11 tons in a shotgun range 12 tons in a rifle range

Introduction Pb content in Florida shooting range soils: 1500 to 70,000 mg/kg FDEP cleanup target for industrial soil: 1400 mg/kg In-situ Pb immobilization using P is cost effective but P application may induce As release Objective: To evaluate the effectiveness of phosphate and Fe-oxide to simultaneously immobilize Pb and As

Selected Florida shooting ranges

Weathered bullets from various ranges

Materials and methods Sampling from mid berm of 6 ranges Treatment 1 short-gun (30 m) 4 rifle (50, 100, or 200 m) 1 (50 m) pistol range Treatment P/Pb molar ratio of 4 2/3rd P from rock phosphate 1/3rd P from H3PO4 With Fe-oxide at Fe/As molar ratios of 0 to 900 Incubated for 3 weeks at field capacity moisture Analyses TCLP- and SPLP-Pb &As XRD analysis for solid samples

TCLP/SPLP Tests Toxicity Characteristic Leaching Procedure (TCLP) Hazardous waste determination under conditions of municipal landfills under RCRA TCLP regulatory limit for Pb and As = 5 mg/L Synthetic Precipitation Leaching Procedure (SPLP) Metal leachability under simulated rainfall SPLP suggested limit for Pb = 15 ug/L; As = 10 ug/L RCRA= Resource Conservation and Recovery Act

FDEP cleanup targets for industrial soils: Pb-1400 mg/kg As-12 mg/kg

TCLP-Pb concentrations in soils with P/Pb molar ratio of 4 TCLP-Pb concentrations in soils with P/Pb molar ratio of 4.0 and various amounts of Fe2O3 Rifle-1 Total Pb: 70,350 mg kg-1 TCLP-Pb: 2,422 mg L-1 Shot-gun-1 Total Pb: 8,150 mg kg-1 TCLP-Pb: 202 mg L-1 Regulatory Limit for TCLP-Pb = 5 mg/L

Pistol-1 Total Pb: 1,538 mg kg-1 TCLP-Pb concentrations in soils with P/Pb molar ratio of 4.0 and various amounts of Fe2O3 Rifle-3 Total Pb: 3,256 mg kg-1 TCLP-Pb: 86 mg L-1 Regulatory limit for TCLP Pb Rifle-2 Total Pb: 12,400 mg kg-1 TCLP-Pb: 226 mg L-1 Rifle-4 Total Pb: 11,490 mg kg-1 TCLP-Pb: 358 mg L-1 Pistol-1 Total Pb: 1,538 mg kg-1 TCLP-Pb: 19 mg L-1

SPLP-Pb concentrations in soils with P/Pb molar ratio of 4 SPLP-Pb concentrations in soils with P/Pb molar ratio of 4.0 and various amounts of Fe2O3 Rifle-1 Total Pb: 70,350 mg kg-1 Shot-gun-1 Total Pb: 8,150 mg kg-1 SPLP Pb (mg L-1) Regulatory limit for SPLP-Pb = 15 g/L

Pistol-1 Total Pb: 1,538 mg kg-1 SPLP-Pb concentrations in soils with P/Pb molar ratio of 4.0 and various amounts of Fe2O3 Rifle-2Total Pb: 12,400 mg kg-1 Rifle-3 Total Pb: 3,256 mg kg-1 SPLP Pb (mg L-1) Rifle-4 Total Pb: 11,490 mg kg-1 Pistol-1 Total Pb: 1,538 mg kg-1 Regulatory limit for SPLP-Pb = 15 g/L

TCLP-As after P and Fe-oxide treatments EPA threshold for TCLP-As = 5 mg/L

X-ray diffraction of phosphate rock and clay fraction of a Rifle-1 range mid-berm soil before and after P-treatment. Cerussite (PbCO3): soluble in TCLP extraction. P-treatment stabilized cerrusite & formed Pb-P crystalline solid phases: Resistant to TCLP extraction.

Summary Florida shooting range soils contained elevated Pb: 1500 to 70,000 mg kg-1 Cerrusite [PbCO3] is the dominant mineral Cerrusite is substantially TCLP-extractable Arsenic is not a major problem in the Florida shooting ranges included in this study except one. Phosphate-treatment can immobilize Pb by: Stabilizing cerrusite Forming new Pb-phosphate crystalline solid phases, resistant to TCLP extraction.

Acknowledgment Funding from Florida Department of Environment Protection (FDEP)