Zoning of the White Sea catchments area by the degree of continental runoff influence on the marine environment

Methodologies for the integral evaluation of the potential impact of continental runoff on the marine aquatic environment have been developed and tested in relation to the catchment area of the White Sea. Integral indicators of pollution potential (PP) and self-purification capacity (SPC) of the river waters have been calculated within the boundaries of the hydrologic areas. The following indicators have been used to calculate the PP: the volume of wastewater and the population density in the catchment area (anthropogenic components of pollution), sediment load (a natural component of pollution). Such natural settings of the catchment as the lake percentage, woodiness and the role of topography in self-purification of rivers have been used to calculate the SPC. The quality of river waters, entering the sea, is the result of the ratio of the proposed integrated indicators. On the basis of the quantitative ratios of PP and SPC, the zoning of the catchment area according to the degree of the negative impact of river waters on water quality in the White Sea has been performed. The resulting zoning scheme is demonstrated as a holistic picture, representing a complex of natural-economic factors on the river catchments of the White Sea basin. It has been revealed that river runoff from a considerable part of the catchment area has not a significant negative impact on the water quality on the White Sea. The greatest pollution effect on the waters of the White Sea has the Northern Dvina River and the Niva River. The obtained data are well correlated with the data of hydrochemical observations in the bays of the White Sea. The objectivity of integrated assessment has been provided by the base on a large number of field data and the exception of the indicators that have not quantitative expression. The obtained results can be used to develop scientifically valid environmental programmes and to plan industrial development in the catchment area.