Vertical And Spatial Distribution Of Major And Trace Elements In Soil Catena At The Central Forest State Nature Biosphere Reserve (Se Valdai Hills, Russia)

Abstract

In this study, we discussed relationship between the vertical and spatial differentiation of 14 chemical elements (total content and three mobile fractions extracted by NH4 Ac, NH4 Ac with 1% EDTA and 1M HNO3 ) and the environmental factors in background Retisols and Stagnosols within a soil catena. In the A soil horizon, the extractability of elements decreased in the series Cd, Mn, Pb> Co, Ni, Cu, Fe> Zn, Bi, As> U, Cr, Mo> Sb. In the O and A horizons, total and exchangeable Mn and Zn were uptaken by plants. In the A horizon, total Bi, Cd, Pb, Sb, Mo, exchangeable As, Bi, Cd, Co, Ni, Mo, as well as As, Cd, Cu, Pb, Zn, Sb bound with Fe-Mn (hydr)oxides were sorbed by soil organic matter; Cr, Fe, Mn formed the organic complexes. In the C horizon, Cd, Fe, Mn, Sb complexes co-precipitated with carbonates. In the Bt horizon, total Cr, Cu, exchangeable Cu, Ni, as well as Cr and U bound with Fe-Mn (hydr)oxides migrated due to the lessivage. On the toeslope’s biogeochemical barrier, exchangeable Zn, Mo bound with complexes, As, Bi, and Fe bound with Fe-Mn (hydr)oxides were accumulated. In the lower part of the catena, peat accumulated the exchangeable compounds of As, Bi, Cr, Fe, Mo, Pb, U. The spatial differentiation of elements became less contrasting from the O and A horizons to the E, B and C horizons.