Modelling the transport of engineered metallic nanoparticles in the river Rhine

“As engineered nanoparticles of zinc oxide, titanium dioxide and silver, are increasingly used in consumer
products, they will most probably enter the natural environment via wastewater, atmospheric deposition
and other routes. The aim of this study is to predict the concentrations of these nanoparticles via
wastewater emissions in a typical river system by means of a numerical model. The calculations rely on
estimates of the use of nanomaterials in consumer products and the removal efficiency in wastewater
treatment plants as well as model calculations of the fate and transport of nanoparticles in a riverine
system. The river Rhine was chosen for this work as it is one of the major and best studied rivers in
Europe. The study gives insight in the concentrations that can be expected and, by comparing the model
results with measurements of the total metal concentrations, of the relative contribution of these
emerging contaminants.
Six scenarios were examined. Two scenarios concerned the total emission: in the first it was assumed
that nanoparticles are only released via wastewater (treated or untreated) and in the second it was
assumed that in addition nanoparticles can enter the river system via runoff from the application of
sludge as a fertilizer. In both cases the assumption was that the nanoparticles enter the river system as
free, unattached particles. Four additional scenarios, based on the total emissions from the second
scenario, were examined to highlight the consequences of the assumption of free nanoparticles and the
uncertainties about the aggregation processes.”
(Citaat: Markus, A.A., Parsons, J.R., Roex, E.W.M., de Voogt, W.P., Laane, R.W.P.M. Modelling the transport of engineered metallic nanoparticles in the river Rhine – Water Research 91(2016), p.214-224)