Soil contamination by plastic particles in the floodplain of the small Danilikha River in an urbanized area

The aim of the study. To assess the content, morphology and surface degradation degree of plastic particles in the Danilikha river floodplain soils in an urbanized area. Location and time of the study. The study was conducted in a recreational area in the projected “Kamensky Square”, located on the left bank of the low floodplain of the small Danilikha River (a left-bank tributary of the Kama River) in the city of Perm. Urban-alluvial gray-humus gley soils were identified in the area. Soil samples were taken from surface horizons in July 2023. Methods. To extract plastic particles from soil we used visual selection, sieving, and flotation in a saturated NaCl solution. The shape and type of plastic particles were determined visually by external features. Natural organic matter was removed with Fenton's reagent. Surface morphology of the of plastic particles and their number were determined using a stereomicroscope. Information-logical analysis was used to determine the relationship between the shape of plastic particles and their sizes. Results. In the combined soil sample from the surface horizons, the number of plastic particles reached 177 pieces/kg (excluding fibers). The mass of plastic particles, including fibers, was 0.7 g/kg. Films prevailed quantitatively among the forms of plastic particles (62%), whereas foam and foam balls made up 34% and 4%, respectively. By mass, particles predominated in the following sequence: foam balls ˃ film ˃ fiber ˃ foam. The size range was dominated by large plastic particles from 1.1 to 15 mm. Specific sizes of plastic particles for different shapes were established. Conclusions. For the first time, the content of plastic particles in the surface soil horizons of the Danilikha river floodplain in an urbanized territory was studied using the case of a recreational zone in the projected Kamensky Square. Plastic particles had different sizes and shapes, which indicated a variety of contamination sources. Contamination of the studied soils with plastic particles can be regarded as moderate. The surface degradation degree of plastic particles indicated their active weathering, which occurs in soil under neutral reaction. The surface degradation of the plastic particles was also actively influenced by external factors that act before plastics enter alluvial soils. To detect soil contamination with plastic particles, we recommend Perm municipal authorities to organize monitoring of plastics content in areas with high anthropogenic pressure.