Analytical techniques for studying soil microplastics

Microplastic pollution has garnered recent attention in the field of environmental science. However, owing to the limitations of samplings, pretreatments, and analytical techniques, the sizes of the detected microplastics are generally large. Quantitative analysis methods are not yet well-developed; thus, the existing publications are incomparable. The analysis of soil microplastics is challenging because of their complex components and surface attachments. To better understand the current status of research and the development trends, the analytical techniques used in soil microplastics research were examined, compared, and summarized for thermal, spectral, and microscopic techniques in this paper. Microplastics have been qualitatively and quantitatively analyzed via spectral analysis, and the dominant techniques are Fourier-transform infrared spectroscopy and Raman spectroscopy. The components and masses have been analyzed via thermal analysis, including pyrolysis gas chromatography-mass spectrometry and thermogravimetric-spectrometry. Shape and size have been characterized via microscopic analysis. Optical and electron microscopies are the most commonly used techniques. The analytical techniques of microplastics are increasing in abundance, but the identification and quantification of soil microplastics remain a complex task. The standardization of analytical technologies is key to evaluating microplastic pollution. Each technique has its advantages and disadvantages, and the combination of analytical techniques is expected to efficiently and accurately analyze soil microplastics qualitatively and quantitatively. Analytical techniques should be selected based on the scientific objective. Meanwhile, some techniques require further exploration and verification for microplastics in real soil.