Plastics and the Ocean. Группа авторов

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



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“fines” abundantly found in seawater that may carry only surface‐adsorbed pollutants. The MPs and NPs with sorbed POPs are well known to be ingested by organisms ranging from zooplankton (Cole et al. 2013; Sun et al. 2017) to whales (Fossi et al. 2014; see Chapter 12), providing a pathway for these chemicals into biota (Hartmann et al. 2017). Particular attention has been paid to marine birds (Fry et al. 1987), where over 25% of the species (Pham et al. 2017), and sea turtles, where all species, are reported to ingest plastics (Kühn and van Franeker 2020). A particular concern is the ingestion of MPs and NPs by commercially important fish and seafood species (see Chapter 13). How the entanglement and ingestion risk of MPs relate to their particle size is illustrated in figure 1.7.)

Image described by caption.

      Source: Adapted from the same report. SEM ‐ Sacnning Electron Microscopy; TEM ‐ Transmission Electron Microscopy; AFM ‐ Atomic Force Microscopy; and AFM‐IR ‐ AFM with infra‐red Spectroscopy.

      Bioaccumulation is the gradual build‐up of the concentration of a compound in an organism relative to that in its environment, due to ingestion or other modes of intake. Biomagnification is an increased concentration of the compound in the predator relative to that in its prey (Miller et al. 2020). A compound that is ingested, but neither metabolized nor excreted at a rate faster than it is consumed by the organism bioaccumulates in its tissue. This is especially true of compounds with a high partition coefficient, (see Chapters 2 and 9). Where the compound is toxic, as with organic mercury, this is a serious concern. Biomagnification results when a predator organism ingests multiple prey organisms, each with a high bioaccumulation of the compound or pollutant (Drollliard 2008; Mizukawa et al. 2009). This leads to a faster build‐up of the chemical compound in predator tissue compared to that in the prey. For instance, when DDT was used liberally, it ended up in the water and invariably in fish. The insecticide was biomagnified in predatory birds such as Ospreys feeding on the fish, resulting in an abnormal thinning of the shells of their eggs.

      A highly bioavailable compound is readily transported from the gut into the systemic circulation. When a contaminated plastic fragment is ingested, the contaminant must leach out in the gut and permeate through the gut wall, for it to be bioavailable to the organisms. Otherwise, it is egested and has a little physiological effect. Bioavailability can therefore also, depend on lipid levels in the diet, the presence of gut surfactants, and the gut pH (Koelmans et al. 2014; Kwon et al. 2017).

      The bioavailability and toxicity associated with MPs in fish have been recently reviewed (Wang et al. 2020). But, the kinetics of leaching and the mechanism of bioaccumulation remains undefined (Qu et al. 2020). It is also reasonable to expect the bioavailability of POPs in the MPs to ingesting animals to be low (Koelmans et al. 2016; Ziccardi et al. 2016), and the MPs may instead even “clean” the gut environment by removing any existing hydrophobic pollutants (Lee et al. 2019; Scopetani et al. 2018). Black Sea Bass (Centropristis striata) presented with PVC pellets loaded with 10 wt% of dioctyl phthalate (DOP) plasticizer, ingested them at the same rate as “clean” or virgin PVC pellets, but the egested pellets showed no change in the DOP level (Joseph et al. 2020). Ingestion of MPs of PE spiked with benzophenone by rotifers, copepods, bivalves, echinoderms also did not result in any toxic outcomes (Beiras et al. 2018). The level of POPs delivered to organisms may be low as the fraction of MPs in the diet has to be minuscule. But, pollutants such as endocrine disruptor chemicals or antibiotics, act at very low concentrations, some displaying a non‐linear dose‐response curves, allowing them to elicit adverse physiological responses at unexpectedly low doses. Also, the physiological effects in these studies were monitored only over the short term. The data taken together do not rule out the possibility of MPs transferring POPs to biota via ingestion, at least in some species.

      The notion of environmental sustainability is a complex one (well outside the scope of this chapter) and according to its original definition, refers to a mode of development that “meets the needs of the present generation without compromising the ability of future generations to meet their own needs.” It is a laudable, qualitative statement, but the strategy to achieve this objective is not clear, especially where development involves depleting a fixed reserve of a natural resource such as rare