Page - 70 - in Freshwater Microplastics - Emerging Environmental Contaminants?

physical-chemical environment (fragmentation, micro-pollutant exchanges) and (2) their interaction with the biological compartment including ecotoxicological effects but also biodegradation. As underlined by Dris et al. [4], the term “microplastics” was used first in the Thompson article to describemainly plastic particles that are “fibrous, 20μmin diameter, and brightly colored.”However, in 2008 another definition ofmicroplasticswith amuchbroader scopewas proposed that included all the particleswith a size smaller than 5mm[5].Although, on the basis of the usual scientific meaning of “micro,” microplastics will describe “micrometric” particles (i.e., 1–1,000μm), for the scientific community, the name “micro”has tobeunderstoodfollowingitsGreekwordμικρo´ς,meaningsmall (i.e., all particles<5mm). This issueofmicroplastics in theenvironment has received increasingattention from the scientists, and the number of articles on this subject increased from less than 10 in 2011 to more than 150 in 2016 (request on Scopus with the words “microplastic”and“environment”).However,microplastics in freshwaterenviron- ments represent only a small fraction of this amount. The first articles on microplastics in freshwater were published in 2011 and focus mainly on Lake Huron [6] and Los Angeles rivers [7] in the USA. Since that period, numerous studies havebeenpublishedcovering all continents,with the exceptionofAntarc- tica, and all the potentially impacted environments (water and sediment for the aquaticenvironment,banks for the terrestrialenvironment).Whileat thebeginning mainly lakeshavebeen investigated, it canbe considered that nowboth lentic and lotic ecosystemsare investigated.Nevertheless, thedynamicsoffibers andplastics inurbancatchmentsandhydrosystemsarepracticallyunknown.Their fate, transfer routes, andprocesses in continentalwater haveyet to bedetermined. Citiescanbeconsideredasoneof themajor sourcesofMPsas theygather at an especially high density all the activities that involve plastics andMPs including textile uses, packaging, transportation, electronics, buildings, and constructions. Theaimof thiswork is toprovideacomprehensiveanalysisof thesourcesandfate ofmicroplastics inanurbanenvironmentwitha focuson theParisMegacity.Often referred to as the Paris agglomeration, thismegacity is one theworld’s 40 largest with a population of over 10million. The Paris agglomeration is crossed by the SeineRiver,whosecatchmentdrainsanareaofapproximately32,000km2fromthe river’s headwaters to Paris. This catchment combines intense anthropogenic pres- sureswith a very limited dilution factor due to the low average flowof the Seine River (350m3 s 1 in Paris). As a consequence, the Paris agglomeration exerts a dramaticpressure regardingpollutants on the river andprovides agoodcase study in order to understand the consequences of urban environments on continental water.Moreover, to our knowledge, there is no case study dealingwithMPs and covering all the compartments of the urban system and fluxes that occur between them. This study on Paris Megacity provides, from our point of view, the most comprehensive overview ofMP sources in an urban area and its interactionwith continentalwater. 70 R.Dris et al.