| Abstract [eng] |
In Europe, as in many other regions, the rapid urbanisation of rivers poses a serious threat to their water quality and survival. The Vijolė stream in Šiauliai is also facing such problems, where anthropogenic loading due to unmanaged sewage discharges is severely altering the ecological status of the stream, which is deteriorating due to the input of excess nutrients into the stream water, as well as eutrophication processes and the emergence of pollution tolerant macrophytes. As a result, a study was carried out to assess the impact of the urbanised areas of Šiauliai on the ecological status of the Vijolė stream, the aim of which was to carry out an ecological assessment of the naturally occurring and anthropogenic nutrient loads in the water of the stream, to determine the abundance and distribution of pollution-tolerant macrophytes, and to assess the ecological status in relation to different chemical parameters. The study was carried out in 2023, sampling water for chemical parameters (COD, total N, total P, Cl-, SO42-, NO3--N, PO43--P, F-) at all times of the year: spring, summer, autumn, and winter, in order to assess the seasonal loading of each chemical at different locations in the stream. The study of macrophyte abundance and distribution was carried out in the late June and August periods, using a quadrant method and dividing the stream channel into 15 different study sites. The assessment of the ecological status, in terms of concentrations of water chemical parameters, was carried out in accordance with the assessment methodology provided by the Ministry of Environment. Studies of anthropogenic chemical loads in the Vijolė River have shown that the most significant contributors to water pollution are elevated concentrations of total and nitrate nitrogen. The concentrations of these nutrients are particularly pronounced in the spring (average 5,1 mg/l) and autumn (average 6,5 mg/l) seasons. For the other chemical parameters (organic matter, total phosphorus, chloride, sulphate, fluoride, phosphate), the anthropogenic load on the water of the stream was found to be low or only momentary. A study of the species, abundance and distribution of macrophytes in the Vijolė River showed that a total of 19 different species were found, 10 of which were indicative of pollution. These included species such as broad-leaved pondweed, water monazoa, small float, blue-margined rush, branching rush, veined mudwort, Canada elodea, curly-leaved float, comb float, marsh lacustrine. The most common macrophytes found were broad-leaved rush and water monazole. The assessment of the ecological status of the water in terms of concentrations of chemical parameters showed that the worst ecological situation in terms of water quality was observed in the section of the Vijolė River flowing away from Architektų St. This section has a potential negative impact on the rest of the stream. |
