FATE AND TRANSPORT OF MICRO- AND NANOPARTICLES IN THE SUBSURFACE

Yingxue Yu

doi:10.7273/000004357

Micro- and nanoparticles, such as plant pathogens, nanomaterials, as well as micro- and nanoplastics, are ubiquitous in the environment, and they can have profound impacts on surrounding ecosystems. The impacts of these micro- and nanoparticles depend on their fate and transport in the environment. The overall goal of this dissertation is to assess the fate and transport of micro- and nanoparticles in the terrestrial environment, particularly, the subsurface environment. The specific micro- and nanoparticles investigated include motile and non-motile Phytophthora zoospores, TiO2 particles, and micro- and nanoplastics. The study with Phytophthora zoospores showed that the transport of Phytophthora zoospores in soil is enhanced by the self-propulsion of zoospores, and the dispersal of zoospores is gen- erally confined in the top of natural soil, but macropores can be a conduit for zoospores, especially motile zoospores, to move to deeper soil layers. The study with TiO2 particles demonstrated that additives in biodegradable plastics, such as TiO2 particles, can be re- leased during composting, and the transport of the released TiO2 particles in the terrestrial environment can be enhanced by compost residues. The study with microplastics showed that the representative elementary volume for quantifying microplastics in terrestrial systems decreases hyperbolically as the microplastic concentration increases. Numerical simulations were used to determine the size of the representative elementary volume as a function of plastic particle concentrations. As biodegradable plastic particles degrade in soil, they be- come smaller and smaller. A numerical model was developed to predict the accumulation of plastic particles due to constant inputs and degradation. Based on the theoretical con- siderations, micro- and nanoplastics generated from soil-biodegradable plastic mulches will likely not cause environmental harm if soil-biodegradable plastic mulches are disposed of appropriately into soil or compost, while they can be of concern when inappropriate disposal or off-site transport happens. Overall, the results of this dissertation highlight the need to consider the uniqueness of different micro- and nanoparticles in order to comprehensively understand and access their fate and transport in the terrestrial environment.

FATE AND TRANSPORT OF MICRO- AND NANOPARTICLES IN THE SUBSURFACE

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