Seite - 72 - in Freshwater Microplastics - Emerging Environmental Contaminants?

In2014, a total of91millionmetric tonsof textilefiberswereproduced [15],of which63millionmetric tonswereman-madefibersand58millionmetric tonswere plastic fibers ( 20%of theworld’s plastic production). 3 SourceandFate ofMicroplastics on theParisMegacity 3.1 Overviewof theApproach Between2014and2016, an investigationof several sources andfluxesofMPshas been carried out on the Paris Megacity. The following sources have been investigated: 1. Atmospheric fallout 2. Runoffwater 3. Graywater 4. Wastewater andWWTPoutlets 5. Combined sewer overflows (CSOs) AmapofParisMegacity aswell as the locationof thevarious sampling sites is presented (Fig.1).Moredetailson themethodologyand theapproachcanbefound inDris [16–18]. One of the challenges of a holistic study is that the different sample typeswill require different samplingmethods. For instance, atmospheric fallout requires the useof a funnel for sampling,while automatic samplers includingpumpingdevices areneededfor the inaccessiblecanalsofwastewaterandCSOs.Theotherdifficulty forsuchasystemicapproachis theinterpretationandcomparisonof theresults.The atmospheric fallout is intrinsically expressed differently than the other compart- ments (fibers per surface and timeunit rather than a concentration).Moreover, the interpretation has to take into consideration the time and space scale differences among the compartments. For instance, atmospheric fallout is a diffusive perma- nent source, whereasWWTP outlets represent a punctual but permanent source, whileCSOsare punctual in timeand space.Thebestway towork around this and be able to understand the sources of MPs is to consider the fluxes between the various compartments, for instance, on an annual basis. In this chapter, a first attempt to describe this approach is presented (Table 1). 3.2 MicroplasticsEncountered in theDifferent Compartments The various concentrations of fibers and fragments encountered in each compart- mentaresynthetizedinFig.2.Thetotalatmospheric falloutwas investigatedat two 72 R.Dris et al.