Gunshot residue is emitted as fine particulate matter during ignition in a firearm barrel. The particulates condense from a vapour phase and contain material from the Pb-Sb-Ba-bearing primer and the Pb-bearing bullet fragments. Shooters can inhale or ingest the fine particulates which also attach to their hands, clothing, and other surfaces. Estimation of the bioavailability of toxic Pb and Sb within the particulates requires detailed knowledge on the mineralogical composition of the particulates and their weathering products. For this purpose, particulates from gunshot residue have been collected from soils beneath a shooting position of a shooting range in Ontario, Canada. Transmission electron microscopy (TEM) shows for the first time that the particulates are composed of Pb-Sb alloys with minor unidentified Ba-bearing phases along the outer rim. Weathering of the particulates results in the formation of incidental nanoparticles of metallic Pb and massicot PbO. The mobilization of these nanoparticles within the soil grain suggest that their release during the weathering of bullets and gunshot residues contribute to the release of Pb into the environment. Hydrocerussite, Pb3(CO3)2(OH)2 is the major secondary Pb-phase in and around the altered particulates. The phase forms during the alteration of metallic Pb and massicot in a Ca-carbonate rich environment. Secondary Sb-bearing phases are valentinite, Sb2O3 and an amorphous Sb-Pb phase (Sb : Pb ratio = 3:1 - 4:1) that has partially replaced large proportions of the Ca-carbonates in the soil grain matrix. The larger abundance of the latter relative to the former phase indicates that its solubility most likely controls the release of Sb into the bulk soil.

Nano-mineralogical study on the weathering of gunshot residue in soils of a shooting range in Ontario, Canada

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.