Plastics and the Ocean. Группа авторов

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Название Plastics and the Ocean
Автор произведения Группа авторов
Жанр Химия
Серия
Издательство Химия
Год выпуска 0
isbn 9781119768418



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in the environment can originate from either textile manufacturing or fabric laundering (Cesa et al. 2020), especially when using top‐loading washing machines. A single wash cycle of a garment (a fleece jacket) in detergent‐free water in a household washing machine releases about 0.3% of its weight as MFs (Hartline et al. 2016) while studies have found 1079 to 106 fibers per kg fabric in five repeated washes to be released into wastewater (Zambrano et al. 2019; Falco et al. 2019). Furthermore, textile fibers such as nylon or polyester can undergo fragmentation consequent to weathering on exposure to solar UVR (Sait et al. 2021). These microfibers can be micro‐ (<100 μm) as well as nanoscale (<100 nm) (Mintenig et al. 2017) and pose a similar threat to marine biota as MPs (Henry et al. 2019). How much fiber exists as debris in the ocean, is difficult to assess, especially because textile fibers are denser than seawater. A recent estimate places it at ~0.2 MMT released annually; as with MPs, the ecological significance of MFs does not scale with the tonnage but with the particle abundance of these in seawater. However, fibers found in seawater collected from six ocean basins turned out to be predominantly (79.5%) cellulosic with synthetic fibers constituting only 8.2% of the microfibers (Cesa et al. 2017). This observation is inconsistent with >50% volume production being synthetic recalcitrant fibers; but the denser synthetics fibers are more likely to be in the sediment. The high percentage of inherently biodegradable cellulosic fiber in the ocean is yet to be explained.

Schematic illustration of density (log particles/m3) of MPs (100–5000 μm) in the different oceans.

      Source: Courtesy Beiras and Schönemann (2020).

      Because 1.5–4.1% of the annual production can end up in the ocean (Jambeck et al. 2015), 7800 MMT of plastics hitherto produced should have resulted in at least 57–160 MMT of plastics in the ocean. However, inventories find less than 0.25 MMT of plastics in surface waters (Eriksen et al. 2014; Van Sebille et al. 2015) and their abundance does not correlate with production volumes over the recent years (Thompson 2004). This disparity has led to the notion of a “missing fraction” of MPs, especially the smaller fragments in the ocean (Kvale et al. 2020; Woodall et al. 2014). However, floating plastics essentially represent a “snapshot” view of the MPs in the short window of time they float before extensive fouling sink them into the water column. Also, the search for a missing fraction assumes that all floating MPs will be larger than the mesh size of collecting gear (around 330 μm) excluding most of the small MPs and NPs from the count. The missing fraction reflects limitations of the sampling gear and not taking into account the MPs below the surface water level, especially in the sediment (Kanhai et al. 2019; Nakki et al. 2019; Ramirez‐Llodra et al. 2011). A recent estimate (though based on only six sampling sites) estimates 14 MMTs of MPs that are >50 μm in the sediment (Barrett et al. 2020).

Litter item Count in millions Plastics typically used
Candy wrappersCigarette filtersBeverage bottlesBottle capsStraws and stirrersCups and platesBags 5.72 3.73 3.67 1.97 1.75 1.39 0.94 PE, PP, PET Cellulose acetate PET PP PE PE, PS, EPS PE

      Data pertain to 36 000 miles of coastline in different global locations. Based on data by Ocean Conservancy on the 2018 Coastal Cleanup.

      1.2.3 Chemicals in Plastic Debris

      Plastics used in products typically include a suite of chemicals intimately mixed with the base resin. These include (i) intentionally added chemicals or additives to modify the properties of the base resin to suit the needs of the product (Groh et al. 2019; see Chapter 2); (ii) low levels of the relevant residual monomer trapped in the plastic (not an issue with PE or PP with gaseous monomers, but relevant with PS, PVC or polycarbonate [PC]); and (iii) unintended compounds sorbed from seawater and concentrated by partition (Hüffer and Hofmann, 2016; Pascall et al. 2005; Rochman et al. 2013; see Chapter 9). Some of these sorbed chemicals are persistent organic pollutants (POPs) that are toxic compounds as well, and remain in the environment for extended durations, allowing them to be widely distributed via water, soil, and air. These tend to accumulate in the fatty tissue of animals that ingest them and may bio‐magnify as they move to higher trophic levels. Any POPs in seafood are of special interest to human consumers. Despite their very low dissolved concentration in seawater, the equilibrium concentration of POPs in the MPs and NPs tends to be very high, reaching concentrations that are ~2 to 6 orders of magnitude higher than in sediment (Mato et al. 2001) or seawater (Wright et al. 2013). Sorption cleans the water of these pollutants but in the process, also generates MPs loaded with POPs, heavy metal compounds, and pharmaceuticals, ingestible by marine biota.