ВПЛИВ ВИЩОЇ ВОДНОЇ РОСЛИННОСТІ НА ВМІСТ БІОГЕННИХ ЕЛЕМЕНТІВ У ЛІМНИЧНИХ СИСТЕМАХ УРБАНІЗОВАНОЇ ТЕРИТОРІЇ

Abstract

There were considered the results of studies of the content of inorganic nitrogen and its compounds, inorganic phosphorus, dissolved silicon and labile iron in the areas of the Verbne and Telbin Lakes, covered with higher aquatic vegetation and free vegetation, as well as with depth. It was found that the content of inorganic nitrogen, ammonium nitrogen, nitrate ions and in some cases inorganic phosphorus was decreased in the thickets of higher aquatic vegetation during the growing season several times compared to areas of the lake without thickets. It was found that higher aquatic vegetation during its growing season reduced the content of inorganic nitrogen in the surface layer of water by 1.1–2.0 times, and inorganic phosphorus in some cases by 1.2–1.5 times, compared with their content in sections free vegetation. The concentration of ammonium nitrogen and nitrate ions in the thickets of higher aquatic vegetation was also 1.1–3.1 and 1.3–2.5 times lower, respectively. From the beginning of the growing season, the concentration of inorganic nitrogen, phosphorus and dissolved silicon in the area of the lake without vegetation was decreased on average from 1.122 to 0.096 mg N/dm3, from 0.250 to 0.075 mg P/dm3 and from 4.1 to 0.31 mg/dm3 and in the coastal area from 1.168 to 0.073 mg N/dm3, from 0.298 to 0.063 mg P/dm3 and from 4.0 to 0.32 mg/dm3 respectively. It was found that the share of nitrate ions in the surface layer of the water of Verbne Lake increased from 9.9% to 68.3% from March to June, and in Telbin Lake nitrate ions dominated, even in March. This was due to the increase in the intensity of the nitrification process. In the first case, this was due to the supply of oxygen during photosynthesis, and in the second case, due to artificial aeration. The effect of higher aquatic vegetation on the content of dissolved silicon and labile iron were not observed. The maximum values content of inorganic nitrogen and phosphorus and dissolved silicon were observed during spring homothermia. Their content in the surface layer of water gradually decreased due to the assimilation of plant organisms with the beginning of the growing season. Direct temperature stratification led to an increase in the content of inorganic nitrogen and phosphorus, dissolved silicon and labile iron in the bottom layer of water due to their inflow from bottom sediments, especially in the absence of dissolved oxygen.