Release, transport and fate of engineered nanoparticles in the aquatic environment

Besides many benefits, nanotechnology brings us a new type of contaminant to worry about: nanoparticles - particles smaller than 100 nm. Silver nanoparticles are used in medical textile, because they kill bacteria. Titanium dioxide and zinc oxide nanoparticles are used as UV filters in sunscreens, and in wastewater treatment to break down organic micropollutants.However, the properties that make them useful in personal care products and water treatment, may make them harmful for organisms in the aquatic environment.
Modeling the release and the subsequent transport helps to understand the risks posed by the use of nanoparticles now and in the future. This was applied to the river Rhine. First, the release of nanoparticles from consumer products was estimated using literature data. Then a mathematical model for the fate of nanoparticles in the aquatic environment was set up, based on data and input parameters collected from published laboratory experiments. This knowledge together with information concerning the hydrology of the Rhine and the wastewater treatment plants in the Rhine basin was used to predict the nanoparticle concentrations under various release scenarios.
The model results suggest that nanoparticles are mostly attached to suspended matter – so-called heteroaggregation being the most important process. Therefore they are transported along with suspended matter and will settle in the sediment if the circumstances allow. To examine the environmental risk of nanoparticles one needs to be able to estimate the release of nanoparticles but also to understand the behaviour of suspended matter.