ASSESSMENT OF SURFACE WATER QUALITY SELECTION OF PRIORITY POLLUTANTS
The dynamics of surface water pollution of the Voronezh reservoir section is studied in accordance with the standard methodology for calculating the specific combinatorial index of water pollution, which takes into account the repeatability and multiplicity of exceeding the maximum permissible concentrations of the studied indicators, as well as their number. The disadvantages of this approach include the calculation of integral water pollution without taking into account the natural hydrochemical background of the reservoir, which does not reflect the cumulative effect of pollutants on the environmental situation. On the other hand, the calculation of the UKIZV relative to background concentrations does not reflect the sanitary and epidemiological situation at the object under study. The averaging of indicators of various effects on water pollution leads to underestimated values of total water pollution due to the "dilution" of more dangerous pollutants by less dangerous ones. For a more accurate assessment of the quality of surface waters at the Voronezh reservoir site, a conditionally natural hydrochemical background was established for 11 studiedindicators. The transition from numerical values of water pollution characteristics for each indicator to a vector space made it possible to develop a single index combining different- dimensional characteristics of water pollution - multiplicity, frequency of excess of the conditionally natural hydrochemical background and the hazard class of the compounds studied. The basis was based on scientifically-based ranks of water pollution presented in standard methods.The developed unified scale of priority of pollutants for the studied reservoir made it possible to establish the most dangerous indicators that make the maximum contribution to surface water pollution in various years of the study. Vector lengths corresponding to the high influence of indicators on water pollution are characteristic of nitrites, COD, BPK5 and dry substances. In recent years, this list has been supplemented with formaldehyde and petroleum products - priority pollutants of the aviation and missile cluster, which reflects the intensification of its activities.The developed integral index of water pollution assumes the summation of the lengths of vectors corresponding only to priority pollutants. It does not take into account those pollutants whose contribution to water pollution is insignificant in terms of a set of parameters (multiplicity of background excess, repeatability, hazard class). The index is limited from below by the value corresponding to water pollution by one indicator with a high impact on water pollution by the totality of the listed characteristics. From above, the index is not limited and depends on the number of priority pollutants. This approach reflects the real ecological situation that has developed on the studied water body relative to the conditionally natural background, allows assessing water pollution taking into account the toxicity of priority pollutants and the effect of their summation, identifying possible sources of water pollution in individual years of research.