Microplastics assessment in
the Krka river estuary surface water

Microplastics (MPs), commonly defined as particles less than 5 mm, are a persistent ubiquitous anthropogenic contaminant that can be found in every environment, making it a global environmental, health, and socioeconomic problem. Due to their high surface area, MPs adsorb toxic pollutants that become bioavailable to organisms upon ingestion as they are often mistaken for food leading to biomagnification (Bule et al., 2020). The sampling area represents the lower part of the Krka River Estuary and is under direct anthropogenic influence from the city of Šibenik runoff waters, nautical and communal ports, city harbor, tourism, mariculture, and fishing. Estuaries and harbors have been recognized as hotspots and transfer pathways for MPs primarily because of the vicinity of the urban environment that emits contaminants from various sources (Miller et al., 2021). The main focus of this research was to determine MPs size, shape, color, surface area, and abundance in surface water using volume-reduced samples collected by a net. Laboratory protocol included sieving, wet peroxidation (H2O2), density separation (saturated NaCl solution), sonication, and filtration. Filter papers were then visually inspected for MPs. Image processing and measurements were carried out with ImageJ/Fiji open-source software.