Nanoplastics (NPs), mainly originated from weathering of microplastics, are ubiquitous throughout the world. However, the environmentally released NPs are still under debate due to the lack of direct proof for the chemical identification of individual nanoparticles. Here, we show an observational evidence of release of heterogeneous NPs from recycled PVC powders (RPP) using a nondestructive analytical method, namely, correlative Raman imaging and scanning electron (RISE) microscopy. The technology achieves direct chemical identification of individual nanoparticles on RPP surface that are as small as 360 nm including nano-PVC and nano-CaCO3 in complexes with pigments. After washing and filtering through a 1 μm poly(ether sulfone) filter, we clearly distinguish nano-PVC from the other components in an air-dried filtrate. Furthermore, the automated 2D mapping of RISE enables the acquisition of the 2D chemical information on a selected area (e.g., 5 μm × 5 μm) and the display of the different components of nanoparticle aggregates without colloidal separation. Our findings give direct evidence and detailed insights in the potential release of nanoplastics from the recycled plastic products. The RISE method will help us intuitively understand the origin, occurrence, and fate of NPs in the environment.
Keywords: Raman imaging and scanning electron (RISE) microscopy; direct chemical identification; environmental release; microplastics; nanoplastics; polyvinyl chloride; single-nanoparticle analysis.