Microplastics monitoring in different environments: separation, physicochemical characterization, and quantification

Multiple environments (such as water and soil) on Earth are contaminated with randomly distributed microplastics (MPs). Wind and water can redistribute MPs from their point sources to diverse locations (such as farmland, lakes, and rivers), thus necessitating simultaneous monitoring. This study systematically investigated the contamination of MPs in the wastewater treatment plant (WWTP), its surrounding water bodies, and the soils around plastic factories. The physical (i.e., shape, size, color, and concentration) and chemical (functional groups) characteristics of MPs extracted from water and soil samples were characterized via physical examination, microscopy, and Fourier transform infrared (FTIR) spectroscopy. Fragments and fibers were the most common MPs shapes in the water environment. The concentration of MPs in the Lanzhou WWTP influent (541.4-648.1 items/L) was much higher than that in the effluent (1.4 items/L) and the Yellow River water (37.8-101.3 items/L). The WWTP has removed more than 99% of MPs from the influent. MPs were mainly made of polyamide (PA), polypropylene (PP), and polyethylene (PE). The average abundances of MPs in the soil surrounding the two plastic factories were 2.7 × 10⁵ and 2.1 × 10⁵ items/ha. In the soil, transparent and fragment MPs were predominant, with polymer types including PP, polybutylene (PB), PE, and polyethylene terephthalate (PET). The results of this study provide a research foundation and valuable data for future exploration of the MPs in multiple environments in understudied regions.