NanoTRACK – Nanoparticle life cycle studies based on [45Ti]TiO2 and [105Ag] Ag0
Within the BMBF-supported joint project NanoTrack (May 2010 to July 2013), partners from industry and research investigated the release of silver and titanium dioxide nanoparticles from surface coatings (nano-composite lacquers). Besides, the research activities focused on the further transport of these released nanoparticles in the environment and investigated processes through to the absorption of the respective nanoparticles by water-borne organisms (e.g. nematodes).
The nanoparticles were labelled with radioactive markers to enable tracing of even smallest concentrations in the highly complex media. Labelling methods allowing the use of radioactively marked nanoparticles in laboratory-scale experiments were developed. To simulate the life cycle of the nanoparticles, nano-composite lacquers were subjected to artificial, hence highly accelerated decomposition. The decomposition products were analysed and their release was traced.
The results revealed that the decomposition products of the investigated lacquer formulations consist of particles with a relatively large size distribution with emphasis on fragments in the range of 150nm and 250nm but also with fraction sizes down to the micrometre range. Besides, the decomposition products did not only consist of the originally used nanoparticles but also contained lacquer base material. The decomposition process, hence, was influenced both by the lacquer base material and the used nanomaterial.
In view of the above, the transport and mobility of the released nanoparticles in the environment strongly depended on the respective water conditions. In the case of relatively hard water, the nanoparticles have a rather low mobility and are removed rapidly from the water through adhesion to geomaterials (e.g. sand) and sedimentation. However, in the case of soft water and also in the presence of natural organic substances (e.g. humic matter), considerable suspension stabilities, which may significantly increase the environmental mobility, can be achieved.
In surface waters, it is particularly due to nanoparticle sedimentation that water-borne organisms living on the ground can get in contact with the nanoparticles and absorb them. The biofilms formed in most cases serve as a food source for further water-borne organisms. Mostly, these are biofilms which then again serve as food for further water-borne organisms. The project showed that e.g., titanium dioxide nanoparticles are absorbed by nematodes and that transport in further food chains, hence, cannot be basically excluded.
