Lead distribution and mobility in a soil embankment used as a bullet stop at a shooting range

The distribution of lead in and below a soil embankment used as a stop butt for lead bullets at a sport shooting range for more than 30 years was inve stigated. A vertical profile, just behind the shooting target, was mapped b y 54 soil samples characterized by contents of lead bullets, soil lead, and easily leachable lead as measured in a leaching test (L/S 2). At the targe t, the soil contained up to 40% metallic lead and 5 to 10% lead associated with the soil particles (< 2 mm). The leaching test showed concentrations o f dissolved lead in the range 5 to 20 mg/ l. However, in the bottom of the stop butt (about 1 m lower than the target) soil lead was only slightly ele vated, and no increase in lead was found below the stop butt in the origina l soil profile. In the lower part of the stop butt, pH was around 5, which is considered to favor lead migration, but in the soil samples with lead bu llets present pH was between 6 and 7. The elevated pH values, probably caus ed by the corrosion of lead bullets, may have been a significant factor in limiting the migration of lead in the stop butt. The investigation showed t hat the lead in the stop butt did not affect the surroundings, but that the high lead content of the soil would require that this be treated as waste if the facility was abandoned.