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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Degradation of Plastic Additives in the Marine Environment

      Like their plastic counterparts, plastic additives are also susceptible to oxidative degradation and biodegradation. The final products from degradation of plastic additives and the kinetics of these processes in the ocean are not well understood. Basic understanding of the effects of UV, oxygen, water, pH, and temperature certainly allow scientists to predict potential degradation/transformation structures to some extent. The biological degradation pathways that can occur in marine environments remain, for the most part, a mystery.

      To write this chapter, we compiled a database of 193 studies that reported concentrations of plastic additives in marine plastic pollution, seawater, marine sediment, and marine organisms from 1978 to 2021.

      2.5.1 Plastic Samples

Schematic illustration of mean concentrations of additives measured in plastics found in the marine environment, shown in logarithmic units of percent content of the plastic sample.

      Plastic goods tend to contain higher concentrations of additives than in preproduction resin pellets, although pellets also contain some additives (Prunier et al. 2019; Teuten, et al. 2009). Plastic debris originating from fisheries, which is a pervasive and large problem (UNEP 2009), had higher concentrations of Irganox 1076, BHT, 2,4‐DTBP, UV320, and UV327, whereas Irganox 1010 was found at relatively higher levels in food‐contact plastic debris (Rani et al. 2017a). These differences stem from the optimal levels selected by manufacturers driven by the desire to make fishing gear as durable as possible in harsh exposure environments and to meet regulations for food packaging. Some concentrations can be lower than the detection limits; and nondetects should never be ignored and were included as zeros while calculating the average additive concentrations, as shown in Figure 2.4.

      A second reason why additives are in lower concentrations than expected is prior leaching from plastic into the environment or degradation of the additive (Rani et al. 2017b; Tanaka et al. 2020). The third reason is some of the additives detected in marine plastic debris could be adsorbed from the surrounding environment rather than being intentionally added. Plastic polymers are routinely used as passive samplers to monitor environmental pollutants in water, because they are excellent at adsorbing compounds from the surrounding environment (Koelmans et al. 2016). Because of this difficulty in determining the source of additives, the use of plastic debris samples to assess global spatial and temporal trends is complicated. Even so, Prunier et al. (2019) noted that mesoplastics from English coastal areas (Massos and Turner 2017; Turner and Solman 2016) or Chinese littoral areas (Wang et al. 2017) had element concentrations in the same order of magnitude as those from the open ocean (Prunier et al. 2019). This differs for organic pollutants, whose concentrations are greater in plastic debris from coastal areas than from the open ocean (Hirai et al. 2011). These findings are likely driven by the global distribution of naturally occurring elements in seawater and point sources influx from human activities in coastal regions (Net et al. 2015).

      2.5.2 Abiotic Samples

Schematic illustration of range of concentrations measured in paired seawater and sediment samples of three plastic additive classes.