The aim of the NANOHETER program is to study and predict the fate of engineered nanoparticles (ENPs) in surface water. Our main working statement is that relevant environmental conditions should be used in this program. Such relevance will be considered regarding both the system composition, and the ENP concentration. These factors mainly determine together the fate scenario of engineered nanoparticles, potentially interacting with the surrounding components of the system. The relevant engineered nanoparticle working concentration is in the microgram per litter range, while the composition of the studied aqueous system includes geogenic minerals, natural organic matter and/or pollutants. Such more relevant conditions are expected to significantly favour heteroaggregation mechanisms, which this project aims at studying.
Affinity studies between ENPs and surrounding suspended matter – This project aims at identifying among the mineral and organic suspended matter occurring in surface water, the components likely interacting with ENPs. These are particulate mineral, particulate or dissolved natural organic matter, and manufactured organic matter such as pesticides.
Heteroaggregation / sedimentation of ENPs with suspended matter in synthetic system – The induced alteration in the fate of engineered nanoparticles in the water column is investigated as a function of the physical and chemical conditions of the medium. A population balance of the ENPs will be established as a function of these conditions considering their different states, or speciation, encountered such as free, adsorbed to suspended matter, heteroaggregated, and sedimented.
Mechanistic Approach – Along these mechanistic investigations, the carried experiment deal with synthetic water systems of well-controlled composition with increasing complexity. This is carried out by introducing more and more interacting components into the studied system, thus tending toward the natural systems.
Holisitic approach – In order to validate this mechanistic approach, a holistic approach is also carried out with natural surface water sampled on field. The suspended particulate and dissolved matter naturally occurring in these water samples were characterised. The fate of engineered nanoparticles in this natural water is studied in terms of potential sorption and heteroaggregation.
Modeling the fate of ENPs in natural surface water – The final aim of this project is to deliver a probability ranking of these potential scenarios that can be used to model the fate of engineered nanoparticles in natural aqueous systems at the river scale. Adapted model approaches is being developed for this purpose, based on population balances between the different reservoirs of the river system, taking into account the heterogeneous interactions of engineered nanoparticles with the surrounding components. The data resulting from the experimental approaches will enable us to better constrain the system modelled in the present task.