Assessing the leaching behavior of different gunshot materials in natural spring waters

Background: Owing to the high environmental risk of lead-based gunshot, especially as the main source of acute lead poisoning in waterfowl, restrictions on its use in European wetlands are being put into place. In order to assess potential risks of alternative gunshot pellets to aquatic systems, we validated a recently published study that compared the leaching behavior of different game shot materials in an artificial solution and their toxicological effects to Daphnia magna. We therefore investigated the altered leaching of shot materials in natural spring waters. Results: The different water conditions (geology/redox conditions) had a strong influence on the leaching behavior of the examined shot types. Spring water originating from siliceous bedrock showed the highest concentrations of nearly all leached metals under aerobic conditions. The results were similar to the former study, which used an artificial standardized medium for daphnids. Conclusions: According to the conducted leaching tests, Cu- and Zn-based as well as Zn-coated gunshot should be avoided by reason of the high risks they pose to the aquatic environment. Furthermore, the use of Pb-based and Ni-alloyed or -coated game shot also should be hampered owing to their impact on birds or other wildlife. Since some of these shot materials are still on the European market, an effective toxicity screening of alternative gunshot materials is necessary. By conducting standardized leaching tests, in addition to chemical compositional standards and toxicity tests regarding birds, the environmental risks of each game shot would entirely be assessed. The method presented in this study provides a further step for initial ecotoxicological risk assessment of gunshot for aquatic systems, since it additionally assesses minor components, like thin coatings, which also can have a high impact to these ecosystems.