Features of the Seasonal Dynamics of Dissolved Nitrogen Forms in the Lower Stream of the Severnaya Dvina River

Abstract— Seasonal (intra-annual) dynamics of the concentrations of nitrate, nitrite, and ammonium nitrogen in the lower reaches of the Severnaya Dvina River were studied. The general features of the seasonal dynamics of the concentrations were determined, and the periods of the maximum levels of dissolved forms of nitrogen in the river runoff were identified. It was found that the concentrations of biogenic elements did not exceed the maximum permissible levels. The percentage ratios of the nitrogen forms in natural waters by seasons were considered.