Читать книгу Plastics and the Ocean - Группа авторов - Страница 13

Anthony L. Andrady

Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA

We live in an era where human beings dominate and control most geochemical processes on Earth’s surface, including some aspects of the ocean system. It is impressive that Homo sapiens accounting for a mere 0.01% of the biomass on Earth, can exert such control; the mass of structures built on Earth by man now exceeds the total biomass on the planet (Elhacham et al. 2020). The present epoch of man deserves to be formalized a distinct period, the Anthropocene, within the geological time scale (Crutzen and Stoermer 2000). This era started in the post‐World War II (WWII) years (Steffen et al. 2015; Zalasiewicz et al. 2016) and is ongoing. Plastics, a unique identifier of the Anthropocene, survives as stratigraphic markers in the soil to guide future archeologists exploring our era. Historical origins of plastics, however, can be traced further back in history, perhaps to 1869, when Wesley Hyatt invented nitrocellulose as a potential substitute for elephant ivory that was used to make billiard balls at that time. Even though Wyeth’s celluloid billiard balls were a failure (as some of them exploded on impact), this unique product opened the floodgate for synthetic plastic products in to the consumer world. But, the commodity plastics we are familiar with today, came of age much later when the War effort spurned a rapid expansion of the materials industry in the US with public funding allowing new plastic resin plants to be built to produce vital plastics for the military supply chain.

Postwar years saw the enthusiastic acceptance of plastics by consumers worldwide, thanks mostly to the efforts of industry to promote plastics as a unique “wonder material,” and much was expected of this novel semi‐utopian material that promised a wide range of affordable products. Today, plastics have emerged as the material of choice in a variety of applications ranging from food packaging to spacecraft design. The abundant societal benefits of plastics (Andrady and Neal 2009) are evidenced by the rapid substitution of conventional materials used in packaging, building, transportation, and medicine, with plastics. Plastics have, by now, become indispensable to the modern lifestyle, with their per capita consumption governed generally by the affluence of the country. While the US, Canada, and Japan, for instance, use over 100 kg per capita of plastics annually, India and some countries in Africa or Central Europe, use less than 50 kg per capita (e‐Marketer 2021). To meet this steadily increasing global per capita demand of an average ~46 kg annually, plastic resin production had grown to 359 million metric tons (MMT); 432 MMT inclusive of the polymer used in synthetic textile fibers) in 2019. China accounted for about 30% of the production, and with ~50% of the global resin demand in Asia, the country is well poised to remain as the leading resin manufacturer in the world. The annual global production of plastics in the year 2015 alone, if processed into a thin plastic “cling film,” was estimated to be large enough to wrap the entire earth in plastic wrap (Zalasiewicz et al. 2016).

An estimated (Geyer et al. 2017) 7300 MMT of plastic resin and fiber was manufactured globally from just after WWII until the year 2015. By 2020, this figure rose to 8717 MMT. More than half of this was either PE (~36%) or PP (~21%). In addition, the thermoplastic polyester (e.g., poly(ethylene terephthalate) [PET]) used in beverage bottles, polystyrene (PS) in packaging, and poly(vinyl chloride) (PVC) as a building material, were also produced. Reflecting their high‐volume use, these same 4–5 classes of plastics typically dominate the plastic content in the municipal solid waste stream (MSW), in urban litter, as well as plastic debris in the marine environment. The current discussion is therefore focused on this limited set of plastic types: PE, PP, and PS foam that dominates floating plastic debris in surface waters of the ocean and nylons or polyamide (PA). PET, PS, and PVC, mostly found in the deep sediment. Deep‐sea sediment is the most important sink or repository of waste plastics that enter the ocean every year. While no systematic quantitative assessment is available, there is little doubt that plastics accumulate in the benthic sediment and a recent estimate places it conservatively at about 14 MMT (Barett et al. 2020).