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)

PyrolysisGC-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 degrees 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.

Automated summary

A pyrolysis GC-ToF-MS-based analytical study was conducted to identify microplastics in the freshwater of Rietvlei dam in Gauteng Province, South Africa. The study found that the microplastics contained different plastic polymers and additives, with PA being the most dominant polymer. The presence of microplastics in the freshwater is likely caused by industrial activities and poor waste management, and it can have negative impacts on the ecosystem and human health.