A model sensitivity analysis to determine the most important physicochemical properties driving environmental fate and exposure of engineered nanoparticles

New insights in the environmental exposure to nanomaterials have been gained from simulations with recently developed multimedia fate models: atmospheric concentrations are relatively low, and sedimentation in the water column is dominated by aggregation with natural particles, whereas soils and sediments are identified as environmental sinks. These model simulations however have only been performed for a limited set of nanomaterials. It is not yet clear to what extent the new insights gained from the limited set of evaluated nanomaterials generally apply to all nanomaterials. A sensitivity analysis was therefore performed of the nanomaterial environmental fate model SimpleBox4nano in order to investigate to what extent its model simulations are driven by the physicochemical properties of a nanomaterial. Sensitivity plots are drawn to quantify how the nanomaterial physicochemical properties specific weight, diameter, Hamaker constant, transformation rate constant, and attachment efficiency with natural particles, relate to (i) simulated key environmental fate processes such as deposition, filtration, and attachment and (ii) predicted free, bioavailable and total concentrations in air, water, sediment and soil. The critical transformation rate constant and attachment efficiency, at which these processes become dominant for prediction of the exposure concentrations are derived. Although exposure modelling is only part of a full environmental risk assessment of ENPs, they deliver insightful results for further development of ERA approaches by indicating to what extent ENP physicochemical properties affect predicted environmental exposure.