Abstract: A field experiment on humic substances and dissolved iron transportation from the water catchment area was conducted in the spring time. The studies were carried out on a small runoff site (2x1m) filled with peat layer of 50 cm deep.During the snowmelt, exclusively a subsurface runoff was formed. The values of distribution characteristics of two main fractions of humic substances – humic and fulvic acids – between the solid phase of peat and water runoff were obtained. It has been shown that the process of complexing with fulvic acids significantly expands migration limits of iron in the dissolved phase. By means of thermodynamic modeling it has been found that the water pH value and the concentration of fulvic acids are the limiting factors for iron’s existence in a dissolved phase.A methodology has been proposed to predict emission of humic substances and iron into water runoff of the Pripyat River (Ukraine).