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Atmospheric deposition of silver in Switzerland decreased significantly between 1995 and 2010, but recent increases in nanosilver production present a potentially new emission source of silver. ’While nanosilver is usually integrated in a robust matrix and its release is either controlled, dampened (highly diluted silver in nanosilver textiles) or prevented (computer modules), point source emissions of nanosilver can occur at the manufacturing sites. The emission of nanosize particles of particular concern because these particles penetrate deeply in the lungs, and have the potential of causing long-term adverse effects to humans. We investigated local silver emission patterns with bryophytes Brachythecium rutabulum and Hypnum cupressiforme and with bulk (dry and wet) deposition measurements of silver, using Bergerhoff samplers, close to a nanosilver manufacturer. With mean values of 0.033 μg g−1, the silver concentrations in the mosses were the same as the background concentration of Switzerland (141 sites). The spatial distribution revealed a decrease in the silver concentrations in moss as a function of increasing distance from the nanosilver manufacturer. The monthly collected bulk depositions were higher in the area of nanosilver production (0.175 ± 0.13 μg m−2 day−1) in comparison to rural (0.105 ± 0.08 μg m−2 day−1) and urban areas (0.113 ± 0.05 μg m−2 day−1) of Eastern Switzerland. Contrary to other areas, the larger monthly variability of the deposition values close to the production site points towards highly variable silver emissions. Subtraction of the silver background deposition results in approximately 60 g deposited silver per year within a perimeter of 4 km from the nanoparticle manufacturer. Along with bulk deposition of silver, we also studied potential morphological changes of the deposited nanosilver. We found silver nanoparticles in the form of environmentally stable silver iodide. We conclude that the applied methods are suitable for monitoring nanometal deposition. Dry nanoparticle production processes can generate atmospheric nanoparticle emissions but they appeared to be small in our investigated case.

Material recycling often leads to environmental benefits when compared to thermal treatments or landfilling and is therefore positioned in the waste hierarchy as the third priority after waste prevention and reuse. To assess the environmental impacts of recycling and the related substitution of primary material, linear steady-state models of physical flows are typically used. In reality, the environmental burdens of collection and recycling are likely to be a non-linear function of the collection rate. This short communication aims at raising awareness of the non-linear effects in separate collection systems and presents the first non-linear quantitative model for PET bottle recycling. The influence of collection rates on the material quality and the transport network is analyzed based on the data collected from industrial partners. The results highlight that in the present Swiss recycling system a very high collection rate close to 100% yields optimum environmental benefits with respect to global warming. The empirical data, however, provided indications for a decrease in the marginal environmental benefit of recycling. This can be seen as an indication that tipping points may exist for other recycling systems, in which the environmental benefits from substituting primary materials are less pronounced than they are for PET. [ABSTRACT FROM AUTHOR]