THE CONTENTS OF NITROGEN COMPOUNDS IN THE TRANSCORDON RIVERS OF THE RIVNE REGION

Abstract

We analyzed the levels of nitrogen compounds entering the cross-border rivers of the Rivne region (on the example of the Styr, Horyn and Lva rivers). The main reason is the discharge of insufficiently purified water by water users. The peculiarities of water use in the region were considered, it includes the intake, use and drainage of water in the basins of the main rivers. Thus, in 2023, 42.769 and 66.14 million m3 were withdrawn from the Horyn and Styr rivers, which have the longest length in the region, respectively, and 29.165 (of which 2.850 million m3 of polluted return water) and 22.324 (of which 2.677 million m3 of polluted return water) were diverted back. In general, in the oblast after the extraction and use of water resources, 13.6% of the return discharge is insufficiently purified and untreated water, which includes pollutants. 86.4% of water is normatively purified and normatively clean without purification. It was found that of the inorganic compounds of nitrogen, nitrates enter surface waters the most, and nitrites enter the least. During 2021–2023, the supply of these compounds with return water discharges decreased: ammonium from 1052 to 742 tons/year, nitrites from 29 to 23.8 tons/year, nitrates from 1437.1 to 1157.6 tons/year. Exceeding the standards of maximum permissible concentrations (MPC) for ponds for fish farming water use by the content of ammonium and nitrites was established in the investigated rivers. Thus, in the Lva River in the period from 2021 to 2023, there was in 1.4–1.7 times exceedance of the maximum permissible limit for ammonium; in the Styr River in 2023 was found a 1.4-fold exceedance of the MPC for nitrites, ammonium in 1.2 (in 2022) and in 1.1 times (in 2021); in the 2023 year, an excess of ammonium by 1.6 times and nitrite by 2.4 times was recorded in the Horyn River. The volumes of discharges of nitrogen compounds into the studied surface waters for the period from 2021 to 2023 were considered. The largest volume of these compounds was discharged into the Lva River in 2021: 1.3 tons of ammonium, 3.8 tons of nitrates. In 2023, these indicators were 0.5 and 3.8 tons, respectively. The most was discharged into the Styr River in 2023: 0.2 tons of ammonium and 3.6 tons of nitrates in 2021, 3.3 tons of ammonium and 1.5 tons of nitrate entered the Horyn River, and in 2023, these figures were 2.0 and 0.3 tons, respectively. We identified the main sources of ammonium and nitrates, namely: for the Styr river basin, it is PJSC “Rafalivskyi karier”; for the Horyn river basin, it is the Ostroh communal enterprise “Vodokanal”, PJSC “Ivano-Dolinsky special quarry”; for the basin of the Lva River, it is the Tomashgorod quarry and the Klesiv quarry the branches of TsUP JSC “Ukrzaliznytsia”.