Metals in soils of erosional systems in forest zone in the central part of European Russia

• The main factor controlling metal contents and distributions is granulometry.
• Metals have generally higher loads in finer fractions (silt and clay).
• We report translocation of sand and losses of finer fractions along the bottoms.
• Slopes may accumulate materials eroded from upper sites.

Small erosional landforms, despite their importance in mass transfer processes, have received insufficient attention in geochemical studies. This paper presents a case study dealing with geochemistry of two small erosional systems, typical of humid moraine landscapes of the central part of European Russia. They are considered as integrated systems comprising several units viz. slopes, bottoms, detrital fans as well as adjacent areas as sources of solid material. Chemical composition of topsoil (total concentrations of Ti, Zr, Mn, Co, Zn, Cu, Pb, Cr, V, Ni, Sn, Sr, Ba and concentrations of the acid-extractable Fe, Mn, Co, Zn, Cu, Pb, Cr, Ni) was used to explore the role of granulometry, pH, organic matter content and transport processes in geochemical differentiation of the systems. Spatial variations in granulometry across the various units indicate a progressive depletion of a finer material in the gully and comparatively invariant distribution of the same fractions within the balka. The granulometry is the main factor controlling the distribution of total and acid-extractable metal concentrations in both systems. The findings imply that the prevailing mechanism of metal migration through the studied systems is a suspension transfer in association with clay and silt particles. The young gully system operates as a transit system and shows higher geochemical differentiation than the aged balka system where some elements may accumulate in topsoil of the lower units of this system.