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The abundance and distribution of microplastics in estuaries have been barely documented, and generally without accounting for the vertical structure in the water column. This study presents the very first data on the occurrence and distribution of microplastics in the Adour Estuary, SW France. The experimental data set was complemented by numerical simulations to gain understanding of the behaviour of suspended microplastics. Microplastics were found throughout the water column with a mean abundance of 1.13 part/m 3 . Films and fragments were the most abundant types of particles collected. Numerical simulations demonstrated that vertical distribution of microplastics in the water column is highly dependent on particle characteristics and on the local hydrodynamics. The main trend is that neutrally-buoyant microplastics are easily flushed out while heavier microplastics are prone to entrapment in the estuary, in particular under low discharge conditions. The present study suggest that estuaries could be a sink of microplastics., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Plastic litter in nearshore waters is an environmental pollutant with increasing impact on coastal environments. At present, knowledge on basic plastic particle dynamics and the interaction with complex hydrodynamics is lacking. The present laboratory study, performed under controlled wave and wind conditions, demonstrates the dispersion of plastics in shallow waters. The study presents a simple case looking solely at cross-shore particle transport. The results show that both wind and waves as well as plastic properties (shape and density) govern the behaviour of plastic litter in the nearshore zone. Heavy particles behave like natural sand with accumulation in the wave breaking zone. Light particles have varying accumulation along the coastal profile depending on the wind, waves and particle shapes. More extensive characterization remains to be done in future studies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)