National reconnaissance of common plastics in Australian biosolids

, Okoffo Elvis, Tscharke Benjamin J., O’brien Jake W., O’brien Stacey, Ribeiro Francisca, Burrows Stephen, Choi Phil M., Wang Xianyu, Mueller Jochen F., Thomas Kevin V..

The extent and scope of how plastics may be introduced into soil systems is not fully understood, however it has been recognised worldwide that they can be introduced into soils through the practice of applying biosolids (treated sewage sludge) to agricultural land. Plastics entering the soil environment through the land application of biosolids have aroused increasing concern as they pose potential threats to soil organisms and health. Although studies have tried to quantify plastics in biosolids, samples usually suffer from an extensive clean-up process to remove organic materials before plastic particles are separated, counted and identified using spectroscopic techniques such as Raman and Fourier-transform infrared spectroscopy. These techniques are size dependent and in many cases are not able to detect nano-sized plastics leading to underestimation. In this study, biosolids samples collected from WWTPs across Australia were analysed to quantify the mass concentrations and profiles of seven common plastics: - PS, PC, PMMA, PP, PET, PE and PVC in biosolids. Plastics were quantified using a validated quantitative method consisting of pressurized liquid extraction (PLE) followed by double-shot pyrolysis gas chromatography–mass spectrometry (Pyr-GC/MS) (Okoffo et al. (2020) to provide the first per-capita mass loads release of these plastics and to evaluate the mass of plastics discharged into the Australian environment. PE was the predominant plastic detected (median, 7.8 mg/g dw), contributing to 69% of the total of all plastics. The results of this work provides a first quantitative estimate of emission of plastics through biosolids end-use in Australia. Reference Okoffo, E. D., Ribeiro, F., O'Brien, J. W., O'Brien, S., Tscharke, B. J., Gallen, M., ... & Thomas, K. V. (2020). Identification and quantification of selected plastics in biosolids by pressurized liquid extraction combined with double-shot pyrolysis gas chromatography–mass spectrometry. Science of The Total Environment, 136924

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