TRANSPORT AND MITIGATION OF MICRO AND NANOSCALE TIRE WEAR PARTICLES IN STORMWATER RUNOFF

Tire and road wear particles (TRWP) are emerging environmental concerns. TRWP is also a leading source of microplastics in the environment, contributing to non-exhaust vehicular pollution emissions that pollute the road and atmosphere. As the first objective, this research comprehensively examines the latest developments regarding these pollutants. The ecological and health impacts, characteristics, quantification, remediation, emission model, and the fate and transport of the TRWP were explored. The exploration revealed that the environmental impact of pollution extends beyond roadside, aerial, waterborne, and soil-settled particles, which have a far-reaching effect on various species. The estimates from the multiple models suggest that more than 50 percent of the TRWP is carried away by stormwater runoff, more than 40 percent of the particles are deposited on the soil, and only a tiny fraction, around 5 percent, remains airborne. In our second objective, we investigate the mobility of micro- and nanosized particles carried by stormwater runoff to various aquatic systems. There, it was revealed that the tiny tire wear particles are not likely to agglomerate in environmental water samples. Critical coagulant concentrations (CCC) were 200 mM, 6.5 mM, and 3 mM for NaCl, CaCl2, and MgCl2, respectively. The high CCC values further indicate that these particles are more stable and mobile in the environment. Moreover, tire particles are likely to be more stable in water samples in colder regions. For our final objective, we investigated the mobility and potential removal of micro-sized tire crumbs from stormwater runoff in the adjacent soil of the road. Our study shows that during heavy rainfall events (approximately 10 mL/min), clean, white quartz sand cannot retain many of the tiny tire particles, and whatever it retains gets washed out by subsequent runoff. The environmental soil has more electronegativity due to organic matter, and we replicated that by adding humic acid (HA) and fulvic acid (FA) to the clean bed filter material. This increased the mobility of the tire particles further. Our research shows that micro and nanoscale tire particles will be highly mobile in soil and water. Without mitigation measures, such as smaller pore-size roadside filter materials and a significant filter bed depth in the