title: Heteroaggregation and sedimentation rates for nanomaterials in natural waters.
abstract: Exposure modeling of engineered nanomaterials requires input parameters such as sedimentation rates and heteroaggregation rates. Here, we estimate these rates using quiescent settling experiments under environmentally relevant conditions. We investigated 4 different nanomaterials (C60, CeO2, SiO2-Ag and PVP-Ag) in 6 different water types ranging from a small stream to seawater. In the presence of natural colloids, sedimentation rates ranged from 0.0001 m d(-1) for SiO2-Ag to 0.14 m d(-1) for C60. The apparent rates of heteroaggregation between nanomaterials and natural colloids were estimated using a novel method that separates heteroaggregation from homoaggregation using a simplified Smoluchowski-based aggregation-settling equation applied to data from unfiltered and filtered waters. The heteroaggregation rates ranged between 0.007 and 0.6 L mg(-1) day(-1), with the highest values observed in seawater. We argue that such system specific parameters are key to the development of dedicated water quality models for ENMs.
authors.affiliation: Aquatic Ecology and Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands; Radboud University Nijmegen, Institute for Wetland and Water Research, Department of Environmental Science, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands; Laboratory for Ecological Risk Assessment, National Institute for Public Health and the Environment (RIVM), P.O. Box 1, 3720 BA Bilthoven, The Netherlands. Electronic address: joris.quik@wur.nl.
authors.forename: J T K
authors.initials: JT
authors.lastname: Quik
authors.forename: I
authors.initials: I
authors.lastname: Velzeboer
authors.forename: M
authors.initials: M
authors.lastname: Wouterse
authors.forename: A A
authors.initials: AA
authors.lastname: Koelmans
authors.forename: D
authors.initials: D
authors.lastname: van de Meent
mesh_terms: D003102:Colloids; D049329:Nanostructures; D012995:Solubility; D014867:Water / Q000737:chemistry*
chemical_list: D003102:Colloids; D014867:Water
keywords: Attachment efficiency; Heteroaggregation rate; Nanomaterial; Natural colloid; Sedimentation