Influence of microfiber properties and environmental processes on their dispersal in estuaries

Lagrangian ocean analysis, where virtual parcels of water are tracked through hydrodynamic fields, provides an increasingly popular framework to predict the dispersal of water parcels carrying particles and chemicals. We conduct the first direct test of Lagrangian predictions for microfibers using: (1) the latitude, longitude, depth, seasonal environmental variability, and distribution of length of microfibers found in the estuary Ria de Arousa, Spain; (2) a hydrodynamic numerical model at 300 m spatial resolution; and (3) a novel three-dimensional particle-tracking model (TrackMPD) that includes processes of dispersion, fragmentation, and sedimentation of plastics in the water column to trace microfibers from potential sources in mussel rafts to geographical sinks. The expected dispersal distances and the expected dispersal times are computed. Microfiber hotspots, both point and diffuse sources of microfibers, are then identified. Remarkably, the role that the environmental processes occurring in estuaries -including riverine outflows, tides, and wind- is playing on the dispersal of microfibers is evaluated and discussed.