| Abstract [eng] |
Autotrophic organisms while in the process of photosynthesis can not function without certain chemical elements, especially Nitrogen and Phosphorus. These elements are called biogenetic, in other words nutritial materials as they limit the inicial biological processes and production. The indication of the quantity of biogenetic elements in water is one of the main hydrochemical parameters which are necessary in the process of evaluation of the state of lakes. The analysis of the dynamics of biogenetic elements is an essential one in order to choose the optimal measures of the management of water quality. The lake Šventas is analysed in this paper. The aim was to establish the dependence of the alternation of water biogenetic parameters on the environmental factors. The work was carried out according to the data of the environmental monitoring. The data on the alternation of water biogenetic parameters in the lake Šventas include the period from 1999 to 2009. The data were provided by the Agency of the Environment Protection. The seasonal alteration of the concentration of Nitrogen and Phosphorus was established: the biggest concentration appears to be in spring and autumn, the smallest incated in summer. In the period from 1999 to 2009 the evident decrease in the concentration of Nitrogen and Phosphorus is indicated. The general concentration of Nitrogen and Phosphorus does not exceed the limits as they were in the times of Grand Duchy of Lithuania and poses no threat to the quality of the water. The alterations of the concentration of Nitrogen can be explained by the active period of vegetation, which happens in lakes in summer. In the beginning of summer, as the startification of the mass of water goes on, plant use up the combinations of Nitrogen, therefore the concentration of it decreases. In spring, as snow melts, the regime of light improves, and the intensive confusion of water brings the biogenetic materials back from sediment to the general mass of water. The alternations of the concentration of Phosphorus is the same as of Nitrogen. The increase of the concentrations can be explained seasonally: the least concentration is during the period of vegetation as the intense photosynthesis is in progress and is the biggest in the cold season when the mineralization of organic materials takes place. Also, a lot of Phosphorus can appear in water with rainfall. |
