Ballent, A., Pando, S., Purser, A., Juliano, M. F., and Thomsen, L.: 
Modelled transport of benthic marine microplastic pollution in the 
Nazaré Canyon, Biogeosciences, 10, 7957-7970, 
doi:10.5194/bg-10-7957-2013, 2013.

Abstract. With knowledge of typical hydrodynamic behavior of waste 
plastic material, models predicting the dispersal of benthic plastics 
from land sources within the ocean are possible. Here we investigated 
the hydrodynamic behavior (density, settling velocity and resuspension 
characteristics) of non-buoyant preproduction plastic pellets in the 
laboratory. From these results we used the MOHID modelling system to 
predict what would be the likely transport and deposition pathways of 
such material in the Nazaré Canyon (Portugal) during the spring/summer 
months of 2009 and the autumn/winter months of 2011.

Model outputs indicated that non-buoyant plastic pellets would likely be 
transported up and down canyon as a function of tidal forces, with only 
a minor net down canyon movement resulting from tidal action. The model 
indicated that transport down canyon was likely greater during the 
autumn/winter, primarily as a result of occasional mass transport events 
related to storm activity and internal wave action. Transport rates 
within the canyon were not predicted to be regular throughout the canyon 
system, with stretches of the upper canyon acting more as locations of 
pellet deposition than conduits of pellet transport. Topography and the 
depths of internal wave action are hypothesized to contribute to this 
lack of homogeneity in predicted transport.

http://www.biogeosciences.net/10/7957/2013/bg-10-7957-2013.pdf