Modelling the exposure of engineered nanoparticles in urban aquatic systems

With the exponential growth of the nanotechnology industry in recent years, concerns about the exposure and potential environmental impacts of engineered nanoparticles (ENPs) have increased. Jointly, due to current increases in the size of urban populations, concerns are rising regarding the associated increase in product waste emission in cities, including novel potential, non-regulated contaminants such as ENPs.
Robust and sensitive analytical approaches for ENPs are still lacking, and therefore only a limited amount of experimental data are available on the ENP emissions and exposure in city environments. However, mathematical models provide a potentially powerful approach to understand the occurrence and fate of ENPs in city environments. While a number of these models already exist, these tend to operate at low temporal and spatial resolution required to fully understand exposure and risks in urban systems. This thesis aims to provide a new modelling approach that allows the estimation of ENPs exposure of urban surface waters at high spatial and temporal resolutions.
As a first step, the sources, release pathways and environmental fate processes of ENPs in urban aquatic systems were reviewed and the gained knowledge was used to design a new integrative modelling framework able to estimate the emissions and exposure of ENPs in surface waters of urban systems with high spatial and temporal resolution. This framework considers the different ENP-product that will be in use in urban systems and both point source and diffuse emission pathways into surface waters.
The proposed framework was then applied to model the spatial and temporal trends of ENP emissions in a case study city (York, UK). The main sources, drivers and activities causing the highest emissions in the city were identified, and emission hot spots and temporal emission trends were derived for the area and period simulated.
Exposure of the York river system to titanium dioxide ENPs (TiO2 ENPs), which were estimated to be the highest emitted ENPs in York, was modelled to develop temporally and spatially resolved potential exposure concentrations in the York river system over time. The results were used alongside ecotoxiological species sensitivity distributions to assess the risk posed by TiO2 ENPs in the York River system.