Microplastic footprints in freshwater ecosystems: Raman spectroscopy of microplastics as indicator of anthropopressure in Northeastern Poland's lakes.

To understand the effect of anthropopressure on microplastic contamination, a comprehensive analysis of Raman spectroscopic measurements conducted on microplastic fibers collected from the freshwater lakes located in Northeastern Poland was performed. Six of the lakes are under protection. Results indicate a diverse array of fiber types with dominant synthetic polymers: polypropylene (PP) and polyethylene terephthalate (PET), as well as numerous organic materials, including cellulose-based fibers (rayon). We found a positive relationship between the amount of microplastic fibers in surface water and the anthropopressure index (IA) calculated for each of the studied lakes. Fiber levels differed significantly between lakes located in protected (33 - 370 items per m3) and urban areas (285 - 845 items per m3). Results indicate that the isolation in protected areas does not shield lakes from airborne microfiber pollution. For five of the lakes investigated results are compared with a previously published study pointing to notable differences in microplastic concentrations detected near shore and in the central part of the lake. Methods of assessing anthropopressure are contrasted and differences in sampling approach are evaluated. Monitoring the abundance and characteristics of microplastics is required to understand their source and patterns of distribution, both of which can be affected by the level of anthropopressure.