Spatiotemporal Regularities of the Background Content of Nutrients in River Water in the Steppe and Forest–Steppe Zones of the Russian Plain

The use of background indicators for monitoring the content of nutrients in surface and groundwater in the steppe and forest–steppe zones of the Russian Plain is substantiated. Approaches to determining the background content of nutrients are proposed. The peculiarities of the formation of the runoff of nutrients during the flood period and summer–autumn and autumn–winter periods are revealed. It is advisable to use the results obtained to assess anthropogenic changes in the content of ammonium nitrogen, nitrate and nitrite nitrogen, and mineral phosphorus in the surface water and groundwater, as well as in wastewater. It is shown that it is advisable to adjust the standards for the content of nitrates and ammonium nitrogen in river and waste waters taking into account the level of the regional natural and anthropogenic background.