The fate of lead in soils contaminated with lead shot

A study of the interactions between lead (Pb) shot and the soil, and the fate of Pb at shooting ranges was conducted in order to address the lack of research on these issues at the current time. Surveys of the spatial and vertical distributions of Pb in the soil were carried out at selected Canterbury clay target shooting ranges. These confirmed that maximum soil Pb concentrations at New Zealand ranges are comparable to those reported overseas, which commonly exceed 10,000 mg kg-1, while in New Zealand the guideline limit for Pb in soil is 300 mg kg-1. There was evidence of Pb movement from the contaminated surface-soil zone into underlying soil. While sufficient Pb had been solubilised from the Pb shot to cause substantially elevated soil Pb concentrations, the majority (68-99%) of the total Pb at each site was present as intact Pb shot >2 mm. An incubation experiment was designed to assess the rate of oxidation of Pb shot and subsequent transfer of Pb to the soil under various environmental conditions. The onset of Pb shot oxidation and subsequent development of the corrosion crust surrounding individual Pb pellets was relatively rapid. Corrosion products in the corrosion crust and precipitated directly onto the soil solid phase readily dissolved over a soil pH range of approximately 4.5-7. Soil solution and fine earth (