Drivers of Pb, Sb and As release from spent gunshot in wetlands: Enhancement by organic matter and native microorganisms

In many countries the use of lead-based ammunition is prevalent, and results in exposure and poisoning of waterfowl and other species of birds. In waterfowl hunting areas large quantities of spent shot may be deposited in wetland and terrestrial habitats. These pellets can undergo transformation, which are influenced by various abiotic and biotic factors. In addition to lead (Pb), other elements like antimony (Sb) and arsenic (As) can be leached from Pb shot into the environment. In vitro simulations that included organic matter and microorganisms were utilized to examine elemental leaching from gunshot. We found that leaching efficiency was the greatest in solutions rich in organic matter derived from artificial root exudates (2.69% for Pb, 1.16% for Sb, 1.83% for As), while leaching efficiency was considerably lower in river water (0.04%). In vitro simulations containing native microorganisms also exhibited greater leaching efficiency (0.49% for Pb, 0.52% for Sb, 1.32% for As) than in ultrapure deionized water and river water. Surface alterations in gunshot included the formation of a weathering crust and secondary phases dominated by carbonates. Spent gunshot is a source of Pb, Sb and As in wetlands that could affect aquatic ecosystems.