MICRO 2020, Fate and Impact of Microplastics : Knowledge and Responsabilities, Lanzarote, ESPAGNE, 23-/11/2020 - 27/11/2020 Microplastics (MPs) in stormwater are poorly investigated. In order to fill this knowledge gap, MP concentrations were investigated in stormwater at the outlet of a runoff water pipe located in Sucy-en-Brie (Paris suburb, France). Stormwater from four rain events were collected (from June 2018 to May 2019). Stormwater flowrates were measured and compared. Three rain events had approximately the same intensity, and one event was more intense. During each rain event, 300 to 500 liters of water were filtered using a plankton net with 80 µm mesh size. MPs are then extracted using SDS and H2O2 30 % digestion followed by NaI density separation (d=1.6 g.cm-3). Blanks were performed to quantify contamination. Samples were filtered on metallic filters with a porosity of 14 µm. Samples were then remobilized on alumina filters and were analyzed using infrared spectroscopy. Infrared mapping analysis are performed on each alumina filters. Maps were analyzed using a microplastic analysis software siMPle, developed by Aalborg University, Denmark and Alfred Wegener Institute, Germany. Preliminary results show a concentration of 3.3-7.5 MPs/L (min-max values, contamination has been considered) during rain events. PP, PE and alkyd are the most prevalent polymers found in those samples. No correlation was found between rain intensity and concentrations. Considering the runoff volumes and the impervious surface area of the studied catchment, this would imply a flux of 4*10^7-9*10^7 MPs.yr-1.ha-1.