Rikosjettfrie kulefang og gummigranulat/dekklipp — bruksmuligheter og miljørisiko

The filler material in a bullet trap has an impact on the risk of ricochets and spread of metals from projectiles in the bullet trap. Rubber granulates and tire chips made from discarded tires may be suitable as filler materials in bullet traps due to the energy absorbing properties of these materials. Rubber granulates and tire chips may contain hazardous substances such as metals and organic pollutants, which may leak from the materials when they are exposed to water. Leaching of pollutants from rubber granulates/tire chips in bullet traps may pose a risk of runoff of pollutants to nearby recipients. To investigate the risk of runoff of pollutants, leaching from one sample of rubber granulates and two samples of tire chips that had been used in bullet traps, and one sample of new tire chips that had not been used in a bullet trap, was tested. Leaching of metals, polycyclic aromatic hydrocarbons (PAH), phthalates and microplastics was measured. Of the metals analysed, mainly leaching of Zn was detected, in addition to some Cu and Pb. The leaching of metals was highest from the rubber granulates and lowest from the new tire chips. Compared to the metals, the leaching of PAH from the materials was low. The leaching of PAH was highest from the used tire chips, and lowest from the rubber granulates. Significant leaching of phthalates was only seen from the rubber granulates. The uncertainty related to the results for microplastics was high, and the analysis only showed results for certain plastic types. The highest leaching of microplastics was seen from the used tire chips, some leaching was seen from the new tire chips, while the leaching of microplastics from the rubber granulates was low. Rubber granulates may be considered as microplastics due to their size. Based on the results of the leaching tests, a risk assessment was done of runoff of pollutants from bullet traps with rubber granulates/tire chips as filler material. According to the risk assessment, it was unlikely that leaching of pollutants from rubber granulates/tire chips in bullet traps will result in concentrations in the recipient exceeding the environmental quality standards for the substances. There may be a risk of spread of microplastics from bullet traps with rubber granulates/tire chips as filler material, but the lack of standardization of microplastics makes it difficult to assess the risk. Compared to bullet traps with sand and soil as filler material, bullet traps with rubber granulates/tire chips may cause higher runoff of some pollutants. However, rubber granulates/tire chips may also reduce the runoff of metals from bullet traps by reducing the risk of ricochets and fragmentation of projectiles. The concentration of particle bound pollutants in runoff water from bullet traps with rubber granulates/tire chips as filler material may be reduced by passing the water through a sedimentation pool. Microplastics and rubber granulates with higher density than water can also be removed from water by sedimentation. Filters designed for adsorption of metals and organic pollutants can be used for treatment of runoff water from bullet traps with rubber granulates/tire chips. Filters can follow a sedimentation step, or be used by themselves in cases where the runoff water contains limited amount of particles.