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Microplastic Contamination in Aquatic Environments: An Emerging Matter of Environmental Urgency

2023

Chubarenko, I.¹

Esiukova, E.¹

Isachenko, I.¹

Zobkov, M.¹

Bagaeva, M.¹

Khatmullina, L.¹

Fetisov, S.¹

10.1016/B978-0-443-15332-7.00005-3

Most of the plastic mass in the ocean is concentrated in coastal zones: large and small plastic items slowly circulate there for a long time, experiencing repeated episodes of beaching/recapture, fouling/defouling, sinking/resurfacing, aggregation, UV degradation, mechanical fragmentation, etc. In this chapter, physical and dynamical properties of marine microplastic particles (MPs, <5mm) are summarized, with relevance to their behavior in the coastal zone. The density range, size classes, and typical particle shapes are presented, and their variation with time is considered. Results of laboratory experiments mimicking mechanical fragmentation of typical plastics in the swash zone are discussed and applied to oceanographically relevant cases. Relations between the mass and the number of generated MPs are experimentally obtained for four plastics typically found in marine environment. Dynamical behavior of MPs is discussed based on knowledge from classical hydrodynamics, marine sedimentology, and physical oceanography. Shape-dependent manner of the particle sinking and the value of the terminal settling velocity are considered, including the influence of vertical convection. Critical velocity of resuspension by a unidirectional flow is addressed, as well as motion of particles in an oscillatory flow under surface waves and in roll structures. Natural sorting of MPs at the shore face is highlighted, which suggests seaward export of smaller MPs, onshore transport of larger particles, and possible arresting of finer MPs below coarser sediment grains. The events of massive wash-outs of seaweed and plastics onto the beaches after severe storms are examined, and the potential of the machine learning methods in prediction of such events is highlighted. Importance of high surface waves, clastic shores, rocky headlands suggests that high-latitude coasts are effective generators of secondary MPs in the World Ocean.

Clastic shores, Convection, Mechanical fragmentation, Microplastics, Oscillatory flow, Resuspension velocity, Sorting, Surface waves, Terminal settling velocity

2024-05-15 14:28:00