Assessment of temporal and spatial inhomogeneity of waters in the Nevskaya Guba Bay and Eastern Gulf of Finland from hydrochemical indicators

Hydrochemical inhomogeneity of waters in the Nevskaya Guba Bay and adjoining water areas of the Gulf of Finland is assessed with a principal component method. The application of the method made it possible to beforehand divide the period of study (1978–1996) into stages and then to single out hydrochemical zones that are formed under the impact of the main factors that take into account the interrelations of 17 water quality indicators. It is demonstrated that spatial water area inhomogeneity at different stages of construction of special structures to protect the city against floods, increased volumes of biologically treated waste waters, and changed sizes of dumping of polluted subsoil is related to various hypothetical factors reflecting different processes in the water body. Whereas before 1993 natural processes of organic matter production and destruction were leading in zone formation, at later stages it was the composition of treated waste waters and processes of the secondary water pollution with phosphate, lead, and cadmium.