Elsevier

Water Research

Volume 201, 1 August 2021, 117367
Water Research

Plastics in biosolids from 1950 to 2016: A function of global plastic production and consumption

https://doi.org/10.1016/j.watres.2021.117367Get rights and content

Highlights

  • Archived biosolids from australia and UK from 1950 to 2016 analyzed for 7 plastics.

  • Increasing concentrations over time of PP, PS, PET, PMMA, PVC and PE.

  • Prior to the 1990s, leakage of plastics into biosolids was limited except for PS.

  • Leakage from 1990s driven by increased production and consumption of PE, PET, PVC.

  • Concentrations of plastics closely correlate with production and consumption.

Abstract

Plastics are ubiquitous contaminants that leak into the environment from multiple pathways including the use of treated sewage sludge (biosolids). Seven common plastics (polymers) were quantified in the solid fraction of archived biosolids samples from Australia and the United Kingdom from between 1950 and 2016. Six plastics were detected, with increasing concentrations observed over time for each plastic. Biosolids plastic concentrations correlated with plastic production estimates, implying a potential link between plastics production, consumption and leakage into the environment. Prior to the 1990s, the leakage of plastics into biosolids was limited except for polystyrene. Increased leakage was observed from the 1990s onwards; potentially driven by increased consumption of polyethylene, polyethylene terephthalate and polyvinyl chloride. We show that looking back in time along specific plastic pollution pathways may help unravel the potential sources of plastics leakage into the environment and provide quantitative evidence to support the development of source control interventions or regulations.

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),

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