Analysis of water quality data of St. Petersburg Olga Osipova Catherine Linkishkina

The goal The data study which we are going to use in our presentation was devoted to the analysis of different water quality series of the small rivers of St.Petersburg in connection with the main sources of pollutants. The water quality parameters of the rivers were analysed & compared with appropriate values of maximum permissible concentrations.

Introduction One of the acute ecological problems in St.Petersburg is decline in the water quality in the Neva river that depends on water quality in its tributaries & in Lake Ladoga. As a result the condition of drinking water supply for 5 million inhabitants & water quality of the Neva Bay is estimated as critical.

Data base The data on the following rivers were studied: Okhta, Chernaya Rechka, Izhora, Slavyanka, Tosna, Fontanka, Moyka, Karpovka, Zhdanovka. The first four rivers are tributaries of the Neva river. The last four rivers are the branches of the Neva river. The selected rivers represent the diversity of all rivers in St.Petersburg.

The data analysis was concerned with the following series of regular observations: Dissolved oxygen (DO) Biological oxygen demand (BOD – 5) Suspended matter Nitrogen (nitrates, nitrites & ammonium) Phosphorus Phenols Oil products Synthetic surface-active matter Metals (copper, lead, manganese, cadmium)

The results For the sake of convenience all the water quality parameters were divided into 3 groups: The most toxic substances: phenols & oil products Metals (copper, lead, cadmium, marganese) BOD-5, phosphorus, DO, suspended matter

Since 1989 the concentrations of phenols have been increasing sharply and now sufficiently exceed the maximum permissible concentration (MPC). In turn the oil products concentrations in the rivers have been lowering during the last years. Moreover, the concentrations of oil products do not exceed the value of MPC.

Trends in the series of manganese & cadmium are not detected & the concentrations do not exceed the values of MPC in the rivers Moyka & Fontanka. The concentrations of manganese in Izhora, Slavyanka & Tosna exceed the value of MPC & do not decrease for the last years. The situation with cadmium in these rivers is normal. The concentrations of manganese & cadmium in the rivers Karpovka, Chernaya Rechka, Zhdanovka, Okhta in the end of the 20’s century were extremely high & exceeded the values of MPC. Now the situation has improved in all rivers except Okhta.

Concentrations of copper sufficiently exceed the value of MPC for all rivers. Extremely high values are observed in the rivers Okhta, Chernaya Rechka, Zhdanovka, Karpovka. The lead concentrations are lower than the value of MPC for all rivers except high peaks in the end of the 20’th century in Izhora & Slavyanka.

The situation in general is normal. The phosphorus concentrations do not exceed the value of MPC & trend is absent. DO concentration are also satisfactory except for the river Okhta where the concentrations are close to the critical values. State of the concentrations of the suspended matter is stable & good. The maximum concentrations are in the rivers Okhta & Slavyanka.

Conclusion General characteristics of the water quality WPI (water pollution index) decreases only for the river Okhta. Analysis of the other rivers did not expose the increasing of the WPI. Nevertheless, some characteristics of water quality of the rivers decrease. It relates to oil products, series from the third group & partly to some metals. Lowering of concentrations of some substances is caused by the reduction of the industry production & only partly by the improving of wastewater treatment system. Therefore, the situation with water quality in St.Petersburg is not satisfactory.

Kate & Olya