Exploring photochemical reactions on anthropogenic surfaces in the atmosphere and aquatic environment

Abstract

The environment is a complex and reactive mixture of chemicals and surfaces many of which are anthropogenic in origin (i.e., human-made). One important class of reactions are those of pollutants on surfaces including on anthropogenic surfaces which are currently understudied. In this thesis, I explore the photochemistry of pollutants on two increasingly important anthropogenic surfaces, brake wear in the atmosphere and microplastics in the aquatic environment, and discuss the potential consequences of this reactivity. In the first part, I quantify the reactivity of brake wear with ozone, which are both important urban pollutants. Brake wear is a major component of vehicle non-exhaust emissions and, following the tightening of exhaust emission regulations and the growing adoption of electric vehicles, is becoming a larger fraction of airborne particles in cities. I show that multiple types of brake wear are all highly reactive with ozone suggesting that the properties of brake wear, such as its toxicity, may be altered over its atmospheric lifetime. I further probe the origin of this reactivity through multiple characterization techniques and investigations into the reactivity of the individual components of brake pads. In the second part, I investigate the effect of microplastic properties on the photodegradation of the sorbed organic contaminant anthracene in the aquatic environment. With the growing plastic industry and lack of adequate waste management, microplastic abundances in the environment are increasing. I show that the properties of these microplastics (polymer type, density, colour, and size) govern the photodegradation kinetics of sorbed anthracene and discuss the processes responsible for these differences. The findings suggest that anthracene will be more persistent on certain types of microplastics, which may consequently have a greater probability of acting as vectors for contaminant transport to remote regions or uptake by aquatic organisms. Anthropogenic emissions are constantly evolving and there currently exist many gaps in the knowledge of their environmental impacts. This thesis presents key insights into the reactivity of two important classes of anthropogenic surfaces, non-exhaust emissions and microplastics, which will be critical to enhancing our understanding of their impacts on air and water quality.