In situ investigation of nanoparticles heteroaggregation processes in surface waters

Heteroaggregation is a key process influencing the fate of both natural and anthropogenic nanoparticles (NPs) in aquatic environments. The interaction between NPs and suspended natural organic or mineral matter can significantly impact their transport and bioavailability. To accurately estimate attachment coefficients on natural surfaces, empirical data are typically obtained from laboratory experiments conducted under highly controlled conditions. However, these experiments often fail to capture the complexity and dynamics of natural environments. This project aims to develop and apply a method for the simultaneous quantification and characterization of heteroaggregates under environmentally relevant conditions and at realistic NP concentrations. Our approach is based on the dialysis bag method, which enables in situ exposure of an NP-partner aggregation system in natural waters. The applicability of this method to a system containing two types of particles will be tested. To achieve this, single-particle counting via ICP-TOF-MS will be employed to: i) Detect and quantify NPs at environmentally relevant concentrations (ng/L). ii) Determine the elemental composition of individual NPs. This approach will allow us to quantify heteroaggregate formation under natural conditions and calculate attachment coefficients specific to different target heteroaggregates, including natural particles, FeOx, clays, and TiO₂ NPs. By providing new insights into the fate of nanoparticles in aquatic environments, this research will contribute to a better understanding of geochemical cycles and the environmental behavior of emerging pollutants.