Hydrochemical Indicators of Water System Analysis as Factors of the Environmental Quality State

Water resources of small rivers are part of the shared water resources and are often the main and sometimes the only source of local water. An important feature of small rivers in the fact is that they are the starting point of the river network, and any changes that occur in their mode, are marked on the hydrological chain. Small rivers form the hydrochemical conditions of water resources and water quality of medium-sized and large rivers, creating landscapes of large areas. The main feature of the small rivers is their close ties with the landscape. Small rivers are the regulators of the water regime of the landscapes, the factors for maintaining balance and redistribution of moisture, as well as the factors that determine the hydrological and hydrochemical specific of medium and large rivers. The aim is the analysis of interaction between parameters of the quality of the water environment like conductivity and nitrates on the example of natural waters of the small rivers. We used the method of correlative analysis which is effective and efficient for the determination of connections between the parameters of water quality that helps to identify sources of pollution, as well as interpret phenomena, forecast the situation related to the change in the quality of natural waters. The hydrochemical monitoring data were obtained from autonomous automated stations that are located on the rivers Bist, Rossel and Mertvovod. We investigated the following correlation dependencies between such combinations of natural waters quality parameters: nitrates and conductivity. Monitoring data are processed using software MS Excel; correlation dependence was defined using the CORREL. Correlation value is changed in the range from −1 to + 1 that demonstrates the indirect and direct dependence between the selected parameters. If the value is closer to +1, this means the presence of a strong connection, if closer to 0—weak. The negative correlation coefficient means the presence of the opposite connection. The time periods for the calculation of the correlation between the parameters of natural waters quality are selected: 4, 8, 16 and 24 h respectively. The following time periods allow the best to trace and predict changes in the natural aquatic environment. Correlation analysis of the concentration of nitrates and conductivity showed that for the r. Bist and the r. Rosselle dominates the positive value of the correlation between the study parameters, which proves their strong interaction. However, at certain concentrations of nitrate-ions observed custom phenomenon of sharp decrease in correlation to the «−1», which is explained by the Onsager equation, namely an excess concentration of nitrates is associated with erosion of different types of fertilizers from the fields as a result of rainfall. Trend analysis of the studied indicators of the Mertvovod water quality was conducted on an average value of each indicator (pH, phosphates, nitrates, BOD, soluble oxygen). We used trend analysis for the Mertvovod because we did not have enough data in time. There was found a significant increase in phosphates with time with a coefficient of correlation R = 0.71, indicating that contamination of the water facility. This can be explained by the arrival of various surface active substances and, to a less extent, the lack of quality sewage treatment facilities. Positive changes are found in water object that is related to a decrease in the value of BOD. This is due to a decrease in the number of oxygen use on oxidation of inorganic and organic substances. In general, the use of river runoff of the river above normal, and the overall environmental state of the river basin is defined as “extremely poor”.