Transformation of the dissolved components runoff in the mouth areas of small watersheds of the southern coast of the Kola Peninsula

The distributional patterns of the dissolved forms of the major ions, biogenic elements, and trace elements were analyzed in the mouth areas of small watersheds of the southern coast of the Kola Peninsula (the stream in the Por’ya Inlet, the Indera River, and the Chavan’ga River). These results were compared to the data obtained under hydrochemical studies performed in the river mouth areas of the White Sea basin. During the productive period, dissolved phosphates (20–46%) and dissolved silica (3–22%) are removed from the continental runoff along the White Sea coast due to the biological assimilation of these elements. The migrations of the major ions, as well as F, Rb, Cs, Sr, Mo, U, and Ni, may be described by the equation of the conservative mixing of the riverine and seawater masses. The distribution of Ba is characterized by pronounced spatial variability and is governed, apparently, by the sorption-desorption processes. An increase of the chloride concentration, which gradually slows down at the marginal filter area, is observed together with the sharp decrease of the Fe, Al, Y, and rare earth elements (La, Ce, Nd, and Dy), as well as for Ti and Zr. Presumably, this decrease is caused by the removal of these elements from the solution by coagulation and flocculation as organic and organic-mineral colloids. The behavior of the dissolved Mn is characterized by specific features in the river mouth areas of the White Sea, including the increase of its concentration at the initial stages of the riverine-seawater mixing, which, in turn, is a result of its desorption from the terrigenous suspended matter. This increase is followed by a nonlinear decrease, possibly, due to the flocculation of colloids.