Qualitative characterisation and identification of microplastics in a freshwater dam at Gauteng Province, South Africa, using pyrolysis-gas chromatography-time of flight-mass spectrometry (Py-GC-ToF-MS)

Bongekile Vilakati; Sivasankar Venkataraman; Hlengilizwe Nyoni; Bhekie B Mamba; Kiyoshi Omine; Titus A M Msagati

doi:10.1007/s11356-022-21510-5

Qualitative characterisation and identification of microplastics in a freshwater dam at Gauteng Province, South Africa, using pyrolysis-gas chromatography-time of flight-mass spectrometry (Py-GC-ToF-MS)

Environ Sci Pollut Res Int. 2022 Nov;29(55):83452-83468. doi: 10.1007/s11356-022-21510-5. Epub 2022 Jun 28.

Authors

Bongekile Vilakati¹, Sivasankar Venkataraman², Hlengilizwe Nyoni¹, Bhekie B Mamba¹, Kiyoshi Omine³, Titus A M Msagati⁴

Affiliations

¹ College of Science Engineering and Technology, Institute for Nanotechnology and Water Sustainability, University of South Africa, UNISA Science Campus, P.O. Box 392 UNISA 0003, Florida 1709, Johannesburg, South Africa.
² Post Graduate and Research Department of Chemistry, Pachaiyappa's College (Affiliated to University of Madras), Tamil Nadu, Chennai, 600 030, India.
³ Geo-Environmental Laboratory, Department of Civil Engineering, Graduate School of Engineering, Nagasaki University, Nagasaki-Daigaku, 1-14 Bunkyo-machi, Nagasaki, 852 8521, Japan.
⁴ College of Science Engineering and Technology, Institute for Nanotechnology and Water Sustainability, University of South Africa, UNISA Science Campus, P.O. Box 392 UNISA 0003, Florida 1709, Johannesburg, South Africa. msagatam@unisa.ac.za.

PMID: 35761140
DOI: 10.1007/s11356-022-21510-5

Abstract

Pyrolysis GC-ToF-MS-based analytical study was employed in the identification of microplastics (MPs) in the freshwater of a dam Rietvlei (RTV) located at Gauteng Province, South Africa. These MPs extracted in five locations of the dam were found to contain five different plastic polymeric constituents including PE, PS, PA, PVC and PET along with phthalate esters and fatty acid (amides and esters) derivatives as additives. Based on the fragmented pyrolyzate products, the contribution of plastic polymers and additives was 74% and 26% respectively. Among polymers, PA was dominant with 52% followed by PVC (16%) and others (13%) such as PE, PET and PS in MPs. Scanning electron micrographs of MPs in this aquatic body displayed the rough and fibrous typed patterns. The residual mass of 8-14% was left after the thermal degradation of MPs in RTV samples in the temperature range of 500-550 °C. The results of thermogravimetry (TGA) and energy-dispersive (EDS) analyses are mutually dependent and coherent to each other by way of demonstrating the presence of various inorganic compounds in the form of additives and/or sorbates. The lessened intensities of carbonyl stretching in PA (1625 cm^-1) and PET (1725 cm^-1) type of MPs attributed the occurrence of degradation and weathering in this aquatic system. The possible causes to the contamination of MPs in this freshwater are the located industries and poor waste management strategies being practised in this densely populated city. Based on the industry, waste management and population perspectives, the increased contamination of MPs is very likely in this freshwater which will drastically affect the ecosystem in the near future. Based on the characterisation results, the presence of various polymers, additives and the metals in MPs is envisaged to deteriorate the aquatic life along with successive risks for the people as a consequence of bio-magnification.

Keywords: Characterisation studies; Freshwater; Microplastics; Pyrolysis GC–ToF–MS.

MeSH terms

Ecosystem
Environmental Monitoring / methods
Esters / analysis
Fresh Water / analysis
Gas Chromatography-Mass Spectrometry
Humans
Microplastics*
Plastics / analysis
Polymers
Polyvinyl Chloride
Pyrolysis
South Africa
Water Pollutants, Chemical* / analysis

Substances

Microplastics
Plastics
Polyvinyl Chloride
Water Pollutants, Chemical
Polymers
Esters