The amount of trace elements in ordinary chernozem and their humic acids (on an example of South Urals)

The amount of some trace elements in ordinary chernozems - the dominant soil type of «Arkaim» reserve (South Ural) and their humic acids (HA) has been carried out. The amount of trace elements being in soil, including heavy metals, is considerable, however the data about maintenance of various amount of trace elements in their humic acids is rather not numerous. The level of humus (the amount of general organic carbon in the top 15-sm layer - 6-9%) and humic acids content of humus horizon in soils studiing is high. Humic acidsfractions 1+2 make the greatest share from the general organic soil carbon of 23-25% in humus horizons. Their own carbon content varies from 50 to 56% from weight of a preparation. Humic acids were allocated from 0,1n NaOH extracts after preliminary decalcition by their sedimentation 2n HCl, with the subsequent dissolution in alkali and resedimentation. The trace elements structure of soils and their major component - humic acids was defined by an atomno-issue spectral method. The amount of separate elements in the same horizons of ordinary chernozems can sometimes differ almost in 2 times (Cr, Mo, V). This fact is marked for soils of steppe and forest-steppe conditions. The concentration variation in big limits of the majority trace elements in the same soil types is connected with distinctions in humus content, рН, absorption capacities, soil structure, CaCO3 content. The average maintenance of defined elements lies in the limits which are not exceeding maximum concentration limit. Though the territory of South Ural tests considerable anthropogenous loading, soils are not polluted. Insignificant excess of maximum concentration limit in ordinary chernozems is revealed only for Mo, Zn and Pb. As and Hg, trace elements that are often met in Southern Ural,s soils aren't found out neither in soils, nor in humic acids.The maintenance of separate trace elements in preparations humic acids has beencounted for soil HA carbon (in mg/kg). The content of the general organic carbon in soil, humic acid percent, the amount of trace elements in HA preparation and mass carbon % in HA was considered for this purpose. Similar recalculation allows to estimate the contribution of humic acids in linkage of trace elements by soils. The order of linkage decreasing of trace elements by humic acids of ordinary chernozem is established: Cu > Mo > Cr > Zn>Ni > Pb > Ti > V. The elements which are not forming associations with humic acids of chernozem (Co, Sb), and also connected with humic acids in insignificant quantities (Mn, Ag) are revealed. The general share of trace elements which have been found out in humic acids, on the average makes about 25% from their general maintenance in soils.

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