THE NITROGEN COMPOUNDS CONCENTRATION IN WATER ECOSYSTEMS OF DIFFERENT TYPES

Abstract

The study researches the changes in the nitrogen compounds concentration (NH4+, NO2¯ і NO3¯) in water ecosystems of different types (the river Stubelka, the Khrinnyky reservoir, Lake Zasvitske and Morozivka quarry) and discusses ecological consequences of their balance shift. The author defines ammonium and nitrites as the predominant form of the nitrogen compounds. It was recorded the exceeding of the maximum permissible concentrations of ammonium nitrogen in the water of river Stubelka (1.16–3.44 times), the Khrinnyky reservoir (1.26-2.06 times), Lake Zasvitske (1.49 times) and Morozivka quarry (1.62 times) that is primarily caused by precipitation, household and agricultural land sewage as a result of mineral and organic fertilizers use. The nitrites concentration exceeds the standard values in the water of the river Stubelka (2.26 times), the Khrinnyky reservoir (1.48-1.77 times) and Lake Zasvitske (3.90-24.64 times) that indicates a slowdown in their oxidation to nitrates and a high risk of secondary pollution of water reservoirs. The nitrates concentration is within the limits of permissible values. It is demonstrated that the nitrogen compounds concentration in water reservoirs changes as follows: NH4+ – river > reservoir > quarry > lake; NO2¯ – lake > river > reservoir > quarry; NO3¯ – reservoir > river > quarry > lake. The balance shift in the ammonium ↔ nitrite ↔ nitrate system towards nitrates is most often characteristic of all water reservoirs in summer and towards ammonium in autumn. NO3¯/NH4+ maximum ratio was found in the Khrinnyky reservoir (94.81), Morozivka quarry (9.55), Lake Zasvitske (5.84) and the river Stubelka (3.80). The pH changes in the water of the river Stubelka (6.7-7.3), the Khrinnyky reservoir (7.0-7.5), Lake Zasvitske (5.9-7.2) and Morozivka quarry (6.5-7.4). The study researches fluctuations in the dissolved oxygen concentration in the water of the river Stubelka (5.7-8.5 mg O2/dm3), the Khrinnyky reservoir (4.4-9.5 mg O2/dm3), Lake Zasvitske (8.6-10.0 mg O2/dm3) and Morozivskyi quarry (8.7-9.3 mg O2/dm3). The concentration of dissolved oxygen in water reservoirs is as follows: lake > quarry > reservoir > river. The presence of an indicator of «fresh» water pollution (ammonium nitrogen) in all reservoirs indicates a constant influx of pollutants, especially intensively to the river Stubelka and the Khrinnyky Reservoir.