Changes in the microplastic content depending on the changes in the river catchment development structure -- preliminary studies.

The problem of microplastics (MP) is increasingly discussed in the context of surface water pollution. Preliminary studies were carried out for an unusual river basin. The researched catchment is characterized by the presence of areas under legal protection and high pressure related to tourist traffic. Three series of tests of microplastic content in the waters of the Upper Vistula were carried out on the section from the Wisła Czarne (above the dam reservoir) to the town of Ochaby. Six sampling points were selected. The research material (suspended solids) was collected using a plankton net with a diameter of 0.25 m and a mesh size of 250 µm, each time from 1 m³ of river water. During the tests microplastics were found in all the taken samples. The least amount of microplastic was observed at sample points 1 and 2. An increase in the microplastic content in the waters of the Vistula was shown, especially in the cities of Wisła and Skoczów. The increase in microplastic content was also observed downstream of the wastewater treatment plant, although it should be noted that it was not as significant as in the case of rivers flowing through the central part of the Upper Silesian Agglomeration. Also noticeable is the decrease in the microplastic content in the samples collected in Ochaby (sampling point 6). This may be caused by both the dilution of the Vistula waters with streams flowing above this point, as well as the natural processes responsible for the removal of suspended solids from the river (sedimentation, retention of suspended particles on the vegetation growing on the river banks or in natural ponds and fragments of the riverbed with reverse current). The Vistula River may be contaminated with microplastics even from their entire length, regardless of whether they flow through legally protected areas, with residual anthropogenic development of the catchment area and the riverbed, or through tourist resorts. [ABSTRACT FROM AUTHOR]