John Wiley & Sons, Ltd.

Press or pulse exposures determine the environmental fate of cerium nanoparticles in stream mesocosms

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Risk assessment models indicate that stream ecosystems receiving municipal wastewater effluent may have the greatest potential for exposure to manufactured nanoparticles. We determined the fate of cerium oxide (CeO2) nanoparticles in outdoor stream mesocosms using 1) one‐time pulse addition of CeO2 nanoparticles, representative of accidental release and 2) continuous, low‐level press addition of CeO2 nanoparticles, representative of exposure via wastewater effluent. The pulse addition led to rapid nanoparticle floc formation which appeared to preferentially deposit on periphyton in low energy areas downstream from the location of the input, likely as a result of gravitational sedimentation. Floc formation limited the concentration of suspended nanoparticles in stream water to <5% of target and subsequent downstream movement. In contrast, the press addition of nanoparticles led to higher suspended nanoparticle concentrations (77% of target) in stream water, possibly as a result of stabilization of suspended nanoparticles through interaction with dissolved organic carbon. Smaller nanoparticle aggregates appeared to preferentially adsorb to stream surfaces in turbulent sections, where Ce concentrations were highest in the press, likely due to stochastic encounter with the surface. Streams receiving wastewater effluent containing nanoparticles may lead to exposure of aquatic organisms over a greater spatial extent than a similar amount of nanoparticles from an accidental release. Exposure models must take into account these mechanisms controlling transport and depositional processes. This article is protected by copyright. All rights reserved

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