MOBILITY AND BIOAVAILABILITY OF LEAD AT A NICHE OUTDOOR SHOOTING RANGE IN WEST CENTRAL INDIANA

Lead is a pervasive environmental contaminant and poses a threat to human health. Ingestion and inhalation of lead from contaminated soil are common exposure pathways. Today, shooting ranges are the second leading source of anthropogenic lead to the environment. Owing to this, as well as the popularity and the prevalence of these facilities, there is an increased risk of human exposure associated with shooting ranges. Therefore, an understanding of the spatial distribution and the transport and the fate of lead in these environments is essential. To investigate this, a study was conducted in the spring of 2018 at a specialized outdoor shooting range located in west central Indiana. This site is unique because only traditional black-powder weaponry (i.e. flintlock and caplock firearms) is permitted. Additionally, cardboard targets are used for the 13.7 m, 22.8 m and 45.7 m target lines, but many steel targets are also placed in the earthen berm that is used as a containment field. The objectives of this study were to identify surface soil lead concentrations, to determine the spatial distribution of lead at the site, to determine the migration pattern of lead, to estimate lead bioavailability, and to determine the site specific soil characteristics that influenced the mobility and bioavailability of lead. The highest average lead concentrations were found in samples collected from the berm. Total lead concentration from the sample collected at the steel target line was >11,000 ppm, which is approximately 13 times greater than the concentration from soils collected where cardboard targets were utilized. All samples collected from the berm and target line areas were >400 ppm. Samples decreased in concentration down grade on the berm as well as with increased distance from the 45.7 m target line. The CEC of the soil was estimated to be between 15-25 meg/ 100g and organic matter constituted 11.2-20.1% of the samples. Soils were found to be mostly alkaline and ranged from 6.91 to 8.46. Bioavailable lead was found to be less than 5% of the total lead concentration, in all but one sample, and a strong positive (r^2 = 0.994) was found between total lead concentrations and percent of bioavailable lead. Formation of lead bearing minerals was also observed as mineral crusts on the surface of exposed bullets in the berm.