Characterization and quantification of engineered and natural nanoparticles in small sub-catchments of Seine River watershed

Engineered nanoparticles (ENPs) are intensively used owing to their remarkable properties related to their small size and large specific surface. Their production leads to their release and accumulation in the aquatic environment and raises concerns about their possible effects and risks. Their detection and quantification are thus needed. However, most studies are performed at high concentrations or/and in simplified matrices. This is not relevant to predicted low environmental concentrations, and also prevents their interactions with natural colloids or particulate materials always found in aquatic systems. Two main techniques were used in this study: asymmetrical flow field-flow fractionation (AF4) and sp-ICPMS. To understand the source, fate and flux of man-made and natural NPs in surface waters, their concentration and size in sampled waters were measured. The campaign was conducted monthly during one year, in three Seine River sub-catchments with different land-uses, ca. forest, agriculture and urban. 4 types of NPs have been selected: Ag, which results mostly from anthropogenic activity, and TiO2, CeO2, La2O3, having both natural and manufactured origins. The results show that the four NPs are present in the three catchments, at the level of 105 to 108 particles/mL, ranging from several ppt to dozens ppb. Except for Ag NPs, the three others have higher concentrations than predicted values by life cycle modeling. Moreover, their concentrations vary as the function of sampling period and site, revealing the effect of climatic conditions and land-use. This work allows us to access to potential process drivers controlling fluxes, observed variations and their origins.