Research Progress on Atmospheric Microplastics: Sampling, Analytical Methods, Occurrence, and Ecological Impacts
Microplastics (MPs), defined as plastic particles smaller than 5 mm, are ubiquitous environmental contaminants with documented presence in urban, rural, marine, remote, and polar atmospheres. The atmosphere serves as a primary medium for their long-range transport, raising concerns regarding climate interactions and human health. This review synthesizes recent advances in atmospheric MPs research, encompassing sampling strategies, pretreatment protocols, analytical techniques, occurrence characteristics, and ecological ramifications. Passive and active sampling methods are delineated, with active samplers enabling quantitative flux measurements. Pretreatment typically involves sequential steps of sieving, density separation, digestion, staining, and filtration to isolate MPs from complex matrices. Identification relies on visual inspection, micro-Fourier transform infrared spectroscopy (μ-FTIR), micro-Raman spectroscopy, laser direct infrared imaging (LDIR), and mass spectrometry. Reported atmospheric MPs predominantly exhibit dimensions below 700 μm, with fibrous morphologies being most prevalent. Color distribution is dominated by black, followed by white and transparent particles. Over 20 polymer types have been identified, with textiles, tire wear, and dust identified as principal sources. Atmospheric MPs can influence solar radiation balance, cloud formation processes, and pose risks to flora, fauna, and human health. However, research remains nascent; standardization of sampling and analytical protocols, along with comprehensive toxicological assessments, are critical knowledge gaps requiring urgent attention.