Plastics in biosolids from 1950 to 2016: A function of global plastic production and consumption
Graphical abstract
Introduction
There has been a sustained increase in plastics production over the past 70 years, increasing from 1.5 million metric tons (Mt) in the 1950s to 359 million Mt in 2018 (PlasticsEurope. 2019, Statista. 2020). The availability of plastics-containing products has grown, with the commercial drivers being durability, cost-efficiency, versatility, elasticity, resilience and longevity (Brahney et al., 2020; MacArthur, 2017). Plastics are used for many applications within a wide range of sectors including; building and construction, transport, packaging, electronics, automotive manufacture or agriculture (PlasticsEurope 2018, PlasticsEurope. 2019, Wang et al., 2019). Whilst the societal benefits from using plastics are extensive and in inexhaustible applications (Andrady and Neal, 2009), plastics as a commodity have been the subject of growing environmental concern (Cole et al., 2011). Contamination of the environment with persistent plastics of all sizes (Li et al., 2020; Ribeiro et al., 2019; Rochman and Hoellein, 2020) is recognized as one of the most widespread and long-lasting anthropogenic changes to the Earth´s biosphere. The presence of plastic particles has been reported in most environments including the marine (Andrady, 2011; Cole et al., 2011; Gigault et al., 2016), freshwaters, such as lakes and rivers (Eerkes-Medrano et al., 2015), sediments (Jiang et al., 2018; Nuelle et al., 2014), soils (Chae and An 2018; Liu et al., 2018; Okoffo et al., 2021), dust and air (Allen et al., 2019; Gasperi et al., 2018; O'Brien et al., 2021).
Previous studies have shown that biosolids from the treatment of sewage are a sink for plastics and are a pathway of plastics release into the environment when applied to land (Corradini et al., 2019; Nizzetto et al., 2016a; Okoffo et al., 2020a; Okoffo et al., 2020b). As global plastics production and consumption continues to increase, without intervention, the release of plastics to wastewater treatment plants (WWTPs) will also likely increase; hence more plastic will enter the environment via this pathway (Corradini et al., 2019; Okoffo et al., 2020b; Rillig, 2020). Estimates suggest that annually 63,000–430,000 t (Mt) and 44,000–300,000 Mt of plastics may be added to farmlands in Europe and North America, respectively, through the application of biosolids (Nizzetto et al., 2016a; Nizzetto et al., 2016b). Similarly, it is estimated that about 4,700 Mt of plastics are released into the Australian environment through biosolids end-use each year, equating to a release of approximately 200 g/person/year (Okoffo et al., 2020b).
There is potential for plastics released to land from biosolids end-use to persist and accumulate in soils due to slow degradation and microbial assimilation (Corradini et al., 2019; Rolsky et al., 2020). From here plastics may transfer to other environments such as rivers, lakes and oceans (Lusher et al., 2017; Nizzetto et al., 2016a). Plastic particles in soils have been shown to affect the health of soil organisms (Huerta Lwanga et al. 2016; Ju et al., 2019; Judy et al., 2019; Rodríguez-Seijo et al., 2018; Rodriguez-Seijo et al., 2017). Similarly, they can alter soil properties, impacting the growth and development of plants by negatively affecting the bulk density of soils, soil structure, nutrition contents, microbial activity and the water holding capacity (Bosker et al., 2019; de Souza Machado et al., 2019; de Souza Machado et al., 2018; Liu et al., 2017; Qi et al., 2018).
Whilst scientific research on plastics pollution is rapidly developing, quantitative measurement of plastics in biosolids has been extremely challenging, and as a result, only a few studies have successfully extracted and quantified plastics in biosolids (Campo et al., 2019; Edo et al., 2019; Ziajahromi et al., 2021). Using a number of different measurement techniques, including microscopy; Raman microscopy and Fourier Transform Infrared Spectrometry (FTIR), previous studies have provided particle count, size, shape, color and partly polymer type-related data in biosolids which may not reflect the total mass concentration of plastics. In view of the limited mass-based concentrations data, and the recent concerns regarding the increasing consumption and release of plastics through biosolids, there is a need to fully understand the release pathway of plastics into the environment on a mass concentration basis. Such data are also required to understand the plastics cycle, from initial leakage from human activities into wastewater and subsequently into biosolids during treatment that are applied to soil (Narain, 2018; Nizzetto et al., 2016a; Nizzetto et al., 2016b; Rillig and Lehmann, 2020, WWT. 2018). How the contamination of biosolids with plastics has changed with time in the context of increasing global plastic production and consumption is currently unknown.
The aim of this study was to quantify the concentration of plastics in biosolids from between 1950 and 2016 to evaluate the historical trend in plastics release and evaluate the relationship between the concentration of plastics in biosolids and global plastic production and consumption. This was achieved through the analysis of archived and contemporary biosolids samples sourced from the United Kingdom (UK) and Australia from the 1950s to 2016 (Donner et al., 2015; Okoffo et al., 2020b). Polystyrene, polycarbonate, poly-(methyl methacrylate), polypropylene, polyethylene terephthalate, polyethylene and polyvinyl chloride plastics were quantified in the historical biosolids samples; constituting >70% of the plastics consumed worldwide (PlasticsEurope. 2019). The results of this study provide the first mass concentration-based quantitative data of plastics contamination in biosolids over time, thereby increasing our understanding of historical plastics leakage into wastewater.
Section snippets
Materials and chemicals
Analytical standards of polyvinyl chloride, polystyrene and poly-(methyl methacrylate) were purchased from Sigma-Aldrich (St. Louis, MO, USA) and low density polyethylene (referred to as Polyethylene) from Thermo Fischer Scientific. Polycarbonate and polyethylene terephthalate were provided by the Norwegian Institute for Water Research (NIVA, Oslo, Norway) and polypropylene was donated by a plastic manufacturer from Melbourne, Australia (LyondellBasell, VIC). Deuterated polystyrene (PS-d5) and
Concentration of plastics in biosolids
Six of the target plastics were detected in the samples analyzed (59 archived samples and the 82 samples included from our previous study (Okoffo et al., 2020b) (Table S1)), while polycarbonate was not detected in any sample (LOD; <0.07 µg/g). The concentrations of total plastics (∑6Plastics) ranged from 0.01 to 14 mg/g dry weight (dw) (median, 4.3 mg/g dw). Polyethylene (0.01–10 mg/g dw) and polyvinyl chloride (0.02–4.6 mg/g dw) were the most abundant plastics, followed by polyethylene
Conclusion
Understanding the historical leakage of plastics into the environment and how this relates to production and consumption will support developing evidence-based strategies to mitigate future plastics pollution. Here we explore archived biosolids from Australia and the UK from between 1950 and 2016, and for the first time provide quantitative mass-based concentration data for seven common plastics over a 70-year period. We show that concentrations of plastics in biosolids closely correlate with
Data and materials availability
All data needed to evaluate the conclusions of this study (except identifiable information about the WWTPs involved) are freely available without restrictions as a data supplement to this article. Additional data related to this paper may be requested from the authors.
Declaration of Competing Interest
The authors declare that they have no competing interests.
Acknowledgements
The authors acknowledge the various wastewater treatment plant operators who kindly provided biosolids samples. Sincere thanks to the Norwegian Institute for Water Research (NIVA, Oslo, Norway) and Lyondellbasell Melbourne (Australia) for kindly providing plastic reference materials. The authors also thank Dr. Michael Gallen for technical assistance and support. E.D.O. is supported by a Research Training Scholarship awarded by the Queensland Alliance for Environmental Health Sciences (QAEHS),
References (74)
- et al.
Pyrolysis Study of Polypropylene and Polyethylene Into Premium Oil Products
Int. J. Green Energy
(2015) - et al.
A Review of the Properties and Applications of Poly (Methyl Methacrylate) (PMMA)
Polym. Rev.
(2015) - et al.
Atmospheric transport and deposition of microplastics in a remote mountain catchment
Nat Geosci
(2019) - Allsopp, M.W. and Vianello, G. (2000) Poly(Vinyl...
Microplastics in the marine environment
Mar. Pollut. Bull.
(2011)- et al.
Applications and societal benefits of plastics
Philos. Trans. R. Soc. B
(2009) - et al.
Predicted growth in plastic waste exceeds efforts to mitigate plastic pollution
Science
(2020) - et al.
Microplastics accumulate on pores in seed capsule and delay germination and root growth of the terrestrial vascular plant Lepidium sativum
Chemosphere
(2019) - et al.
Plastic rain in protected areas of the United States
Science
(2020) - et al.
Multidecadal increase in plastic particles in coastal ocean sediments
Sci. Adv.
(2019)