Identification and Characterization Methods for Microplastics Basing on Spatial Imaging in Micro-/Nanoscales

Microplastic pollution is a global problem in recent decades due to their ubiquity in the oceans, sediment, soil, or wastewater. The bioavailability and adsorbability for toxic chemicals of MPs have detrimental effects upon living organisms. This work attempts to provide a critical overview on modern instrumentation and promising techniques for identifying and visualizing micro- or nanoplastics. Fourier transform infrared spectrum (FT-IR) and Raman spectroscopies combined with microscopies, scanning electron microscopy (SEM), hyperspectral imaging (HSI), and confocal laser scanning microscopy (CLSM) were widely used in the identification and visualization of microplastics in organisms and environments. The advantages and limitations of each identification and characterization method were indicated for MP analysis basing on spatial imaging in micro-/nanoscales. In addition, some novel methods may possibly be applied to micro-/nanoplastics identification, such as atomic force microscope (AFM), which may be used to identify and characterize the surface morphology, chemical composition, thermal and mechanical properties of MPs at the nanoscale. However, there is a need to improve and develop new methods to reduce the identification time and effort for sub- or nanomicron plastics and obtain more useful physical and chemical information in environmental MPs.