Assessment of the oxygen regime, nitrification processes, trophicity and toxicity levels of minor stream water

Summary

The assessment of the level of pollution and the level of trophicity with nutrients depending on their concentration in a minor stream – the Sodyshka River was carried out. It is shown that in terms of the concentration of ammonium nitrogen and mineral forms of nitrogen, the watercourse throughout its entire length falls in the category «eutrophic»; whereas, in terms of the level of pollution with mineral phosphorus, only some the sections of the river downstream the Yur’evetskaia poultry farm and the mouth can be attributed to the eutrophic category. Permanganate oxidizability and chemical oxygen demand (COD) were used to define the degree of pollution of the watercourse with organic substances of various origin. It is shown that the river is classified as «very dirty» in terms of the total oxidizability (COD). It was found that in 62.5% of water sampling points the oxygen saturation rate (OSR) was below 60% indicating the low quality of water in the stream and low rate of oxidation of organic and inorganic substances in the hydroecosystem. The results of the correlation analysis showed that resistant to oxidation (non-oxidative by microbiota) allochthonous substances have the greatest effect on the degree of water saturation with oxygen (correlation coefficient 0.98). Based on the results of field studies of the concentration of various forms of mineral nitrogen, the intensity of nitrification processes in the river water was calculated. To identify the toxicity of water to zooplankton, zoobenthos, and fish, the aggregation index was used that defined the exceedance of the maximum permissible concentration of the main forms of nitrogen for fishery waters. Judging by the value of the aggregation index, the river water turned out to be toxic.

Key words

toxicity , biogenic elements , permanganate oxidizability , minor stream , oxygen regime , trophicity level , nitrification intensity , correlation dependences