Pathways for degradation of plastic polymers floating in the marine environment.

By Berit Gewert, Merle M. Plassmann, M. MacLeod. Environmental Science: Processes & Impacts, 2015

1,694 citations recorded by the source corpus.

Each year vast amounts of plastic are produced worldwide. When released to the environment, plastics accumulate, and plastic debris in the world's oceans is of particular environmental concern. More than 60% of all floating debris in the oceans is plastic and amounts are increasing each year. Plastic polymers in the marine environment are exposed to sunlight, oxidants and physical stress, and over time they weather and degrade. The degradation processes and products must be understood to detect and evaluate potential environmental hazards. Some attention has been drawn to additives and persistent organic pollutants that sorb to the plastic surface, but so far the chemicals generated by degradation of the plastic polymers themselves have not been well studied from an environmental perspective. In this paper we review available information about the degradation pathways and chemicals that are formed by degradation of the six plastic types that are most widely used in Europe. We extrapolate that information to likely pathways and possible degradation products under environmental conditions found on the oceans' surface. The potential degradation pathways and products depend on the polymer type. UV-radiation and oxygen are the most important factors that initiate degradation of polymers with a carbon-carbon backbone, leading to chain scission. Smaller polymer fragments formed by chain scission are more susceptible to biodegradation and therefore abiotic degradation is expected to precede biodegradation. When heteroatoms are present in the main chain of a polymer, degradation proceeds by photo-oxidation, hydrolysis, and biodegradation. Degradation of plastic polymers can lead to low molecular weight polymer fragments, like monomers and oligomers, and formation of new end groups, especially carboxylic acids.

Subfields: Biomaterials, Industrial and Manufacturing Engineering, Pollution

View Paper: https://www.semanticscholar.org/paper/1f307652fab7d25caf33ff64764d47b594e599a0

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In Biomaterials

1. Ren Wei
2. S. Thakur
3. S. Tamulevičius
4. V. Thakur
5. W. Zimmermann

In Industrial and Manufacturing Engineering

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2. T. Hoellein
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In Pollution

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Citations in the corpus

• Dissolved organic carbon leaching from plastics stimulates microbial activity in the ocean (2018, positive): “The quantity of plastic waste entering the oceans is predicted to increase by up to one order of magnitude by the year 2025 (20) resulting in plastic-derived DOC of up to 236,000MT per year in the global ocean, with potential major consequences for marine microbes and the carbon cycling in the ocean”
• Micro‐by‐micro interactions: How microorganisms influence the fate of marine microplastics (2020, background): “However, while oxygen and light dependent pathways drive plastic degradation, plastics buried in marine sediment will be exposed to euxinic conditions (Andrady 2011; Gewert et al. 2015).”
• Microbial enzymes for the recycling of recalcitrant petroleum‐based plastics: how far are we? (2017, background): “The degradation process of plastic waste causing serious environmental damages can be expected to be considerably different in landfills, terrestrial and marine environments (Kyrikou and Briassoulis, 2007; Andrady, 2015a; Gewert et al., 2015).”
• Recent developments in recycling of polystyrene based plastics (2018, background): “This results la ndfilling of plastic waste and leads to the hard environmental issues [6].”
• Microplastic-Associated Biofilms: A Comparison of Freshwater and Marine Environments (2018, background): “In comparison with biopolymers, traditional plastics (such as PE, PET, and PP) will persist for even longer within aquatic environments (decades or centuries; [11, 63, 64]), with biodegradation typically preceded by abiotic weathering [24, 65].”
• Rethinking microplastics as a diverse contaminant suite (2019, background): “Fragmentation is mediated by the polymer type and environmental conditions, which can be highly variable (Sivan 2011; Gewert et al. 2015).”