[The parameters of selective sorption of Со, Сu, Zn and Cd with sod podzolic soil and chernozem]
2009
Kruglov, S.V., kruglov@itkom. obninsk.org | Anisimov, V.S., [email protected] | Lavrentieva, G.V. | Anisimova, L.N., All-Russia Research and Development Inst. of Agricultural Radiology and Agroecology, Kaluga Region (Russian Federation)
There were used soils selected for arable layer of agricultural lands: cultivated sod podzolic mean loamy soils (soil 1) (the Kaluga region) and leached chernozem (soil 2) (the Lipetzk region). Test portions of air-dried and sieved soils were added with 20 ml of solutions with an increasing amount of relevant heavy metal (Co, Cu, Zn, Cd). The content of heavy metals was analyzed by atomic emission spectrometry with inductively coupled plasma. Sorption models were used to describe the connection between dissolved and absorbed forms of heavy metals. To establish the selectivity of ion exchange of heavy metals/calcium there were used 2 models based on the mass-action law equations. Both soils more preferably bind heavy metals than calcium, but the selective exchange coefficient value depends on the mole ratio of ions in the solution, the nature of heavy metals, soil type and properties. The sorption process involves at least 2 types of functional centers, differing in selectivity of exchange of heavy metals/calcium 100 times and more. The plots with low sorption selectivity are wide spread and determine the cation exchange capacity (CEC) of soils. They are located on the surface of crystallites of soil minerals carrying an uncompensated negative charge. The relative contribution of high selective centers to CEC is small (1.5-6.5%) and only for Cu reaches 16%. Humus macromolecules containing functional groups capable of forming not only ion but covalent or donor-acceptor links have such centers. That is, simple models represent information which can be a basis for better understanding the behavior of heavy metals in sorption and ion-exchange processes, but conclusions relative to the properties of sorption of different heavy metals in this soil, or said heavy method in different soils can notably differ.
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