Concentrations of Chemical Elements in the Water and Suspended Matter of the Northern Dvina River and the Annual Gross Runoff to the White Sea

The results of four years of continuous investigations (from May 2015 through April 2019) of the elemental composition of the water of the Northern Dvina River are presented; the water sampling was performed monthly year around at two sites in the lower reaches. More than 50 major and trace elements were determined in filtered water (0.45-µm membrane filter) and in suspended matter on filters, as well as C org on GF/F glass fiber filters. The ICP MS and AAS methods were applied. The most important outcome is that the average weighted concentrations of elements in the water discharge (dissolved forms) and in suspended matter discharge (suspended form) were obtained in contrast to most similar previous publications; the average weighted concentrations allowed us to consider these results to be the most close to real. The C org and Fe concentrations in waters of the Northern Dvina River are three- to fivefold higher compared to the average concentrations of these elements in the rivers of the world. This has a natural explanation, which includes the features of the watershed basin (widespread distribution of wetlands). The presence or absence of a correlation between elements and organoferric colloids significantly determines their concentration. The average content of elements in riverine suspended matter is very similar to the global levels, except for organic carbon and P. The annual element discharge for every year of study and the four-year average for two forms of matter (dissolved and suspended) were calculated.