Influence of Organic Compounds on Ni, Co, Cu, Cr, and Pb Accumulation by Nodules in Agro-Dark-Humus Podbels (Planosols) in the South of Primorskii Region

The involving of organic compounds in accumulation of Ni, Co, Cu, Cr, and Pb by Fe–Mn nodules in agro-dark-humus podbels (Planosols (Aric)) under different types of long-term agrotechnical impact has been studied in the south of Primorskii region. The profile patterns of the level of SOC content in soils and in nodules indicate the active deposition of organic compounds in nodules in the lower parts of soil profiles in the of fallow and phytomeliorative variants of the experiment. Fulvic acids were noted to predominate in the composition of humus in the nodules in these variants. The long-term application of organic fertilizers contributed to the decrease of SOC incorporation into nodules and to the increase of the part of humic acids in nodules. Nodules were characterized by a high accumulation levels of Co and Pb in all variants of the experiment. Accumulation of Ni, Cr, and Cu was recorded in nodules from particular horizons of studied soils. The intensity of elements accumulation in nodules of different variants of the experiment varied. Accumulation of Ni was controlled by the content of Mn-containing compounds. The most active sorption phases of nodules from soils with a longer period of organic matter transformation (fallow variant and long-term addition of manure variant) were Fe-containing and organic compounds.