Control of lead solubility in soil contaminated with lead shot: Effect of soil pH

An incubation experiment was carried out to assess the rate of oxidation of Pb shot and subsequent transfer of Pb to the soil under a range of soil pH conditions. Lead shot corrosion was rapid, so that soil solution and fine earth (<1 mm) Pb concentrations increased rapidly within a few months. Corrosion products, dominated by hydrocerussite (Pb3(CO3)2(OH)2), developed in crusts surrounding individual Pb pellets. However, irrespective of pH, Pb2+ activities in the soil solutions, modelled using WHAM 6, were much lower than would be the case if they were controlled by the solubility of the dominant Pb compounds present in the Pb shot crust material. In contrast, modelling of soil solid–solution phase distribution of Pb, again using WHAM 6, suggested that, at least during the 24 months of the study, soil solution Pb concentrations were more likely to be controlled by sorption of Pb by the soil solid phase.