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Water course quality in St. Petersburg according to government agency "St. Petersburg Center of hydrometeorology and environmental monitoring with regional functions"

For more than three decades Severo-Zapadnoye UGMS has been carrying out watercourse pollution monitoring in St. Petersburg. For the majority of watercourses in the city river stations of observations are located in estuarial areas (fig.1) where polluting and biogenous substances are accumulated, transported by river waters from the catchment area, and the pollution specifics and indicators for water objects are defined by the character and scope of economic activity.

For hydrochemical analyses the water samples are collected in 18 stations of the Neva River and its inflows. From 1995 to 2004 a part of works on hydrochemical monitoring were carried out by request of the Administration of Saint Petersburg.

Before 2006 the Roshydromet system the classes of water quality were used as the integrated characteristic of he surface water impurity estimated by the "water impurity index" (WII) (Fig. 2). It's calculated is carried out for each point (station) according to the formula:

WII = ∑ (С1-6 / PDK1-6) / 6 where C/PDK - relative (rated) average annual concentration; 6 - strictly limited number of indicators (the substances taken for calculation and having the highest relative average annual concentrations, including dissolved oxygen and BPK5 (pesticides don't count in WII). "Very pure" waters belong to the I class (WII less or equals 0.3), "pure" - the II class (WII from 0.3 to 1), "moderately polluted" - the III class (WII from 1 to 2.5), "polluted" - the IV class (WII from 2.5 to 4), "dirty" - the V class (WII from 4 to 6), "very dirty" - the VI class (WII from 6 to 10) and "extremely dirty" - VII (WII more than 10).

The classes of water quality in the main watercourses in St. Petersburg calculated on the basis of WII are given in the Table.
Since 2006 Severo-Zapadnoye UGMS has been transferred to the new system of surface water quality assessment - the Specific Combinatorial Water Impurity Index (SCWII). The following indicators are counted during SCWII calculation: repeatability of impurity cases (frequency of detection of the concentration exceeding the maximum permissible concentration), average value of frequency rate of exceeding the maximum permissible concentration (average results of the analysis of saples exceeded the maximum allowable concentration, without samples not exceeding maximum permissible concentrations). Particular estimated points (Sα and Sβ) – conditional values – are calculated for each of these indicators. The product of estimated points is the generalized estimated point (S). The sum of the generalized estimated points on all substances in one station is the combinatorial water impurity index (CWII). SCWII is calculated as CWII divided by number of the substances counting in this assessment.

You can get more detailed information on surface water quality in St. Petersburg from the annual analytical review "Environmental protection, environmental management and ensuring environmental safety in St. Petersburg" issued by the Committee on environmental management, environmental protection and ensuring environmental safety of the Administration of St. Petersburg. One can find this publication in all large libraries in the city: Central city public Library named after V.V. Mayakovsky, National Library of Russia, Library of the Russian Academy of Sciences, central regional libraries and university libraries.

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