Seite - 71 - in Freshwater Microplastics - Emerging Environmental Contaminants?

2 TypesandShapes ofMicroplastics:AFocusonFibers inUrbanAreas? MPsobservedinfreshwaternotonlycoverseveralordersofmagnitudeinsize, they alsocoverawidespectrumofshapes.This includesfibers (length diameter)and fragments (diameter thickness) composed of different irregular shapes and spheres. These can be considered as either primary or secondaryMPs depending on their origin. Primary MPs are already manufactured in a size smaller than 5 mm. Two different forms of primary MPs exist: preproduction pellets and microbeads. Preproduction pellets are used in plastic industry. These virgin resins aremelted and then formed intoconsumerproducts [8].Microbeadswerefirst present inhand cleaners that are used on rare occasion by the average consumer [9].Microbeads have also come to replace natural exfoliatingmaterials in facial cleansers, which areoftenusedonadailyorat leastweeklybasis[10].SecondaryMPsstemfromthe degradation and fragmentation of large debris. Thermal, mechanical, and photo- degradation are important factors during the fragmentation process [11, 12]. Weconsider textilefibers to represent a special case.Theycanbeconsideredas secondaryMPs as they come from the breakdown of large items (clothes). This breakdown does not primarily occur in the environment but in the washing machinesduringthelaundry[13].Asaconsequence,fibersarefoundinthedisposal of washing machines and, like primaryMPs, enter the environment in a micro- scopic size.The samestudyshowed thepresenceoffibers at thedisposal ofwaste- water treatment plants (WWTPs). As a consequence, we would expect a predominance of fibers in urban areaswith largeWWTPs. In addition, because of the complexity of studying fibers, they are often overlooked. It is here decided as consequence togive a specific attention tofibers. Fibers are often not included on the key figures concerning plastic materials [14]. However, a great proportion of the produced fibers are derived from petro- chemical polymers. The international organization for standardization (ISO/TR 11827:2012 Textiles – Composition testing – Identification of fibers) proposed a classification of thefibers according to their nature andorigin. Fibers thatareusedandcommercializedcanbeeithernaturalorman-made.The natural fibers are categorized according to their origin into animal, vegetal, or mineral fibers. For instance, cotton is a vegetal natural fiber and is very widely used.Man-madefibersareobtainedbyamanufacturingprocess.Theartificialones aremade by the transformation of natural polymers. For example, rayon is artifi- ciallymanufacturedbut ismade fromcellulose,which isanaturalpolymer.On the other side, synthetic fibers are made from polymers that were chemically synthetized. In this latter category, we can find plastic polymers (polypropylene, PP;polyamide,PA;polyethersulfone,PES;etc.).The latteraremostoften theonly fibers that are included in the microplastics definition in the different studies. Bicomponent fibers also exist and are composed of two fibers forming polymer components,which are chemically and/or physically different. Sources andFate ofMicroplastics inUrbanAreas:AFocusonParisMegacity 71