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

摘要

The distribution of lead in and below a soil embankment used as a stop butt for lead bullets at a sport shooting range in Denmark for more than 30 years was investigated. A vertical profile, just behind the shooting target, was mapped by 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 target, 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 of dissolved lead in the range 5 to 20 mg/litre. However, in the bottom of the stop butt (～1 m lower than the target) soil lead was only slightly elevated, and no increase in lead was found below the stop butt in the original soil profile. In the lower part of the stop butt, pH was～5, which is considered to favour lead migration, but in the soil samples with lead bullets present pH was between 6 and 7. The elevated pH values, probably caused 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 that 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.