Seite - 74 - in Freshwater Microplastics - Emerging Environmental Contaminants?

surface coefficient is about 27%.At the outlet of this catchment, stormwaterwas collected during five different precipitation events between October 2014 and March 2016. Runoff concentrations at the catchment outlet ranged between 24and60fibersL 1withanaverageof35fibersL 1.Byconsidering therainwater volumes collected during the atmospheric fallout experiments, amedian concen- tration of 40 fibers L 1 of rainwater can be estimated. Fragments of plastic were also recovered in the runoff on three of the five sampled events and consisted mainly of foamyand irregular shapes.Concentrations ranged from<2 to 16 frag- mentsL 1.Thenumberof fragmentswas systematically lower than thenumberof fibers, and there is no correlationbetweenboth types ofMPs. MPswerealsoanalyzedatvariousscalesof thesewersystem: fromtheoutletof washing machines to the outlet of WWTPs (unpublished data except for few samplesofoneWWTPoutlet [18]).Washingmachineeffluentshavebeencollected at four volunteers’ homes. The washings were carried out in their own washing machineswith their own items. To have amore realistic vision, participantswere asked to not change anything from their habitual washing process. Therefore, clothesmadefromnatural, artificial, andsyntheticfiberswereall included,without any preselection. Concentrations between 8,850 and 35,500 fibers L 1 were encountered compared to 120 and 810 fibers L 1 for control washes (without clothes), confirming the large amount of the fibers disposed of in washing machines’ effluents. The wastewater entering fourWWTPs of the Paris agglomeration was consi- dered. Generally, wastewater is highly contaminatedwith fiberswith the average concentration being of 248 109 fibers L 1 (mean SD, n¼ 20) reaching a Fig. 2 A synthesis of the total fibers and fragment concentrations in the investigated urban compartments as well as the fluxes of synthetic fibers between different compartments. Only data about total fibers (natural fiber like cotton + artificial and synthetic fibers) are available for CSOsandrunoff, and therefore the latter isnot includedin thesyntheticfiberfluxestimations [24] 74 R.Dris et al.