Characteristics of microplastics in municipal solid waste incineration ash in South Korea

Fly and bottom ash samples from 18 municipal incineration facilities were analysed to investigate the generation of microplastics (MPs) during plastic waste treatment. MP concentrations in ash differed by incineration method. The number of MPs in ash was quantified using micro-Fourier transform infrared spectroscopy, yielding 13-122 particles g^-1 in fly ash and 6-946 particles g^-1 in bottom ash. MP mass concentrations were measured using pyrolysis-gas chromatography/mass spectrometry, and ranged from 1.53-8.54 μg g^-1 in fly ash and 2.51-72.21 μg g^-1 in bottom ash. The average MP abundance in total incineration ash differed by incineration method: 350, 436, 105, and 170 particles g^-1 for general incineration, high-temperature incineration, high-temperature melting, and pyrolysis facilities, respectively. The corresponding MP masses were 28.39, 19.82, 6.68, and 13.43 μg g^-1. Nine polymer types were detected, with polyethylene, polypropylene, and polyester appearing most frequently. Based on measured MP concentrations and ash generation, total MP emissions from incineration ash were estimated at 2.07 t a^-1.