Can incineration completely eliminate plastic wastes? An investigation of microplastics and heavy metals in the bottom ash and fly ash from an incineration plant

The content of (micro)plastics and heavy metals were investigated in the fly ash, bottom ash and surface soil samples from a municipal solid waste incinerate plant. The abundance of microplastics was 23, 171, and 86 particles/kg dw, respectively. The type of microplastics in fly ash was fiber, and the main type in bottom ash and soil samples was fragment (43.0% and 29.3%), followed by film (26.3% and 25.0%), foam (13.0% and 25.1%), and fiber (17.7% and 20.7%). Most of the microplastics had obvious tearing marks, with the protrusions and scratches on their surfaces. Several types of heavy metals such as Cr, Cu, Zn, Pb were adsorbed on the surface of microplastics. Additionally, the column test demonstrated that the microplastics and heavy metals in the bottom ash can be significantly dissolved out under the impact of external precipitation. Results also indicated that acid rain precipitation easily dissolved heavy metals into the water environment from the bottom ash without special treatment or protection. This paper investigated the combined migration of microplastics and heavy metals from the bottom ash, which can provide theoretical basis for further study of properly treating the bottom ash and exploring the environmental behavior.