MSCA-COFUND-CLEAR-Doc-PhD Position #CD22-31: Anthropogenic fibers, Microplastic and Tire Wear Particles in stormwater: comparison of the contamination levels and impact of stormwater management practices between France and Canada

Since the 1980s, numerous studies have demonstrated that urban stormwater contributes to the deterioration of the quality of receiving environments. Early investigations of stormwater more generally focused on aggregate parameters and nutrients, as well as conventional pollutants such as metals and polycyclic aromatic hydrocarbons. During this last decade, investigations of stormwater by a wide range of metallic and organic pollutants were carried out. These pollutants include many pesticides, endocrine disruptors such as phthalates, alkylphenols, and bisphenol A, and priority pollutants of the European Water Framework Directive (Gasperi et al., 2022).

Very recently, following studies demonstrating that microplastics, plastic particles < 5 mm in size in any one dimension are widespread in marine and freshwaters, and may also have negative ecological impacts, question raise on the microplastic issue in urban hydrosystems and more especially in stormwater. Some recent experimental studies suggest nevertheless that urban stormwater runoff can be a significant pathway for microplastics in the environment. Although numerous sources of plastic in urban stormwater are indeed found (tire wear, road wear, plastic litter, artificial turf, paints, building materials, footwear, pre-production pellets and powders, industrial waste, spills from trash collection, and landfill leachate), knowledge on the contamination of stormwater by microplastic is very limited.

In the past, urban stormwater runoff received little to no intentional treatment before discharging. By replacing the traditional stormwater management paradigm, green infrastructures which are fully promoted, have been advanced as an innovative, complementary strategy to reduce pressure on stormwater systems and secure cleaner runoff to water bodies. The benefices of green infrastructures in microplastic mitigation in comparison to the other stormwater water management practice, if it is expected, remains unknow. However, these knowledges are of prime importance to both identify the microplastic pathways, and to design and elaborate appropriate mitigation strategies at various levels of decision making (national, regional, and local).

In close collaboration the Department of Civil and Mineral Engineering of The University of Toronto (Canada) and the Water, Environment and Urban Services Laboratory (Paris, France), the overall objectives of this PhD is to investigate and compare the pollution of urban stormwater by microplastics both in France and in Canada and assessing in-depth the impact of different stormwater strategies (traditional stormwater control systems vs. green infrastructure, or between different green infrastructures such as stormwater ponds, bioretention cells, etc.). Both laboratories have strong expertise and international recognition on this subject and have already published papers (Smyth et al. 2021 – 31 citations and Treilles et al. 2021 – 19 citations). The novelty of this work is to combine the assessment of stormwater quality for one emerging class of pollutants in France (Nantes and Paris) and Canada (Toronto), and to compare different stormwater strategies by studying contrasted monitoring sites in both countries.

Different definitions of microplastic are nowadays available. Depending on the organization (WHO, US-EPA, etc.), in addition to the microplastic fragments which are systematically considered in the studies, the definition can also include microfiber pollution released form the wearing and washing of textiles made from synthetic and non-synthetic fibers, as well as tire wire particles emitted during regular vehicle use due to the friction occurring between tires and the road surface. Here, we proposed to adopt a very large definition of microplastic by investigating anthropogenic fibers (synthetic and non-synthetic fibers), microplastic and tire wear particles. Investigating in the same time such a broad range of microparticles in runoff is one major strength since the rare studies dealing with microplastics in stormwater generally consider only one of the three sub-categories. In France and Canada, microplastic and anthropogenic fibers will be analyzed by infra-red micro spectroscopy (µ-IRTF) following a co-constructed and validated protocols between the different labs. Tire wear particles will be analyzed only in France by Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS).

The knowledge provided by this work are of prime importance to both identify the microplastic pathways, and to design and elaborate appropriate mitigation strategies at various levels of decision making (national, regional, and local). By investigating the impact of green infrastructures in comparison to the tradition stormwater management paradigm, such a study will provide data and support for the enhancing resilience in the built environment.