Characterization of lead in soils of a rifle/pistol shooting range in central Florida, USA

The distribution of lead in soil samples collected from both surface (0 to 10 cm) and profile (O 0 to 10 cm, E 11 to 30 cm, Eb 31 to 50 cm, Bw 51 to 100 cm, and C 181 to 200 cm) at a 14-year-old rifle/pistol shooting range located in central Florida were determined using EPA Method 3051a (microwave, HNO3/HCl=3:1, v/v). In addition to total lead analysis, Toxicity Characteristic Leaching Procedure (TCLP) analysis was performed on corresponding samples to determine whether the soils would require special handling as hazardous waste if the soils were to be removed from the range. Total lead in surface soils varied from 330 to 17 850 mg, Pb kg(-1), with the greatest concentration in the middle of the backstop berm. The TCLP tests indicated that lead in all surface soils exceeded the 5 mg Pb L-1 critical level of federal regulation for solid wastes and hazardous wastes provided by the Resource Conservation and Recovery Act (RCRA) and would be characterized as hazardous waste. Sequential fractionation and X-ray diffraction (XRD) analyses revealed that lead carbonate existed predominantly (91.3%) in the berm soil. The weathering of lead bullets in the soil environments formed primarily as hydrocerussite (Pb-3(CO3)(2)(OH)(2)), with small amounts of massicot (PbO) and cerussite (PbCO3). However, the elevated soil pH, caused by the oxidization and transformation process of elemental lead in lead bullets, could be a significant factor in limiting the migration of lead in the soil.