Estimation des flux de plastiques transitant en Seine: Quelles méthodes pour quels résultats ?

Global estimations state between 1 and 10 million metric tons of plastic entering the oceans each year. But, they are associated with great uncertainties due to methodological difficulties to accurately quantify plastic fluxes from continent into oceans. New studies at basin scale are thus needed to improve model calibrations. Here, a modelling approach based on JAMBECK's statistical method and a field approach are compared in order to (i) quantify plastic fluxes in the Seine River and (ii) constrain uncertainties and their origins of the both approaches. Despite the simplicity of the statistical approach and rough extrapolations, both methods yield similar results, i.e. between 1,800 and 5,900 t/yr of plastic flowing into the Seine River. Whereas about 100 t/yr of plastic litter are removed by involved NGOs, which is a small fraction of the estimated flux. According to the MSFD (2008), actions are undertaken to quantify plastic fluxes entering the oceans. Among different methods, a better use of the data from the waste collection by NGOs should be considered. The development of a national and homogenous platform listing all the collects could be a first step in that direction.