title: Simplifying modeling of nanoparticle aggregation-sedimentation behavior in environmental systems: a theoretical analysis.
abstract: Parameters and simplified model approaches for describing the fate of engineered nanoparticles (ENPs) are crucial to advance the risk assessment of these materials. Sedimentation behavior of ENPs in natural waters has been shown to follow apparent first order behavior, a 'black box' phenomenon that is insufficiently understood and therefore of limited applicability. Here we use a detailed Smoluchowski-Stokes model that accounts for homo- and heteroaggregation and sedimentation of ENPs and natural colloids (NCs), to simulate and interpret experimental ENP aggregation-sedimentation data. The model adequately simulated the observed time and initial concentration dependence of CeO2 settling data, and also predicted the conditions for aggregation rate-limitations of overall removal. Heteroaggregation with natural colloids was identified as the dominating removal process. Finally, the empirical apparent first order model data were calibrated against the mechanistic Smoluchowski-Stokes model simulation data, showing excellent fits for a range of NC initial concentrations. Using first order removal rates thus can be considered a valid and informed approximation when modeling ENP fate in the aquatic environment.
authors: Wageningen University, Aquatic Ecology and Water Quality Management Group, P.O. Box 47, 6700 AA, Wageningen, The Netherlands. Electronic address: joris.quik@rivm.nl.
authors: Joris T K
authors: JT
authors: Quik
authors: Radboud University Nijmegen, Institute for Wetland and Water Research, Department of Environmental Science, P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands; National Institute of Public Health and the Environment RIVM, P.O. Box 1, 3720 BA, Bilthoven, The Netherlands.
authors: Dik
authors: D
authors: van De Meent
authors: Wageningen University, Aquatic Ecology and Water Quality Management Group, P.O. Box 47, 6700 AA, Wageningen, The Netherlands; IMARES - Institute for Marine Resources & Ecosystem Studies, Wageningen UR, P.O. Box 68, 1970 AB, IJmuiden, The Netherlands.
authors: Albert A
authors: AA
authors: Koelmans
mesh_terms: D002563:Cerium / Q000737:chemistry; D003102:Colloids / Q000737:chemistry*; D004777:Environment; D008962:Models, Theoretical; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology; D009930:Organic Chemicals / Q000737:chemistry
chemical_list: D003102:Colloids; D009930:Organic Chemicals; D002563:Cerium; C030583:ceric oxide
keywords: Engineered nanomaterials; Exposure modeling; Heteroaggregation; Homoaggregation; Natural colloids; Sedimentation