Temporal Dynamics In Microplastics Within An Indoor Environment: Insights From A Novel Tape-Lifting Method

Abstract: Microplastics (MPs) constitute a risk to both human and environmental health. It is vital to identify sources and pathways to take the necessary action and limit the number of MPs in our environments. However, we currently have a limited understanding regarding MPs' variation with time in urban environments in an indoor setting. This knowledge gap is partly due to the absence of standard sampling procedures, and there is a need to develop reliable sampling techniques. This study evaluates the effectivity of a novel tape-lifting method developed for sampling MPs from various urban surfaces and applies this technique to measure weekly trends in artificial polymer deposition within an indoor environment at Umeå University. Two stone floor surfaces were sampled repeatedly on eight occasions over three weeks. Recovered MPs were identified in a microscope and categorized after shape: fibers or fragments. My developed tape-lifting method showed high MP recoveries (on average 100 ±4%) for the majority of the tested indoor surfaces (floors and tables). However, the method proved less functional for outdoor substrates (asphalt), where the recovery was significantly lower (on average, 48% ± 17). In my monitoring of MPs, I found that the deposition rate of fibers did not significantly differ between the two sampling sites or change over the three weeks. In contrast, MPs of fragment-type varied both between sampling sites and as a function of time. Here, the MP deposition rate was, on average, nearly two times higher at one of the sites, indicating substantial spatial variation. Regarding temporal variation, fragmented MPs showed an overall decrease in the number of deposited fragments over the three-week period. Interestingly the lack of variation in fibrous MPs indicates a dominating input source of fibers that is both homogenous for the room and static with time. In contrast, a specific source that is also time-sensitive appears to influence the dispersal pattern of fragmented MPs. My findings highlight the need to consider the temporal dimension of MP contamination and for research focusing on the relationship between fragmented MPs and their sources in indoor environments.