Results migration mobility investigation of microelements in the soil horizons under the influence of humus and carboxylic acids

Abstract

Formation of regular soil profiles podzols of boreal zone is defined by extracting features of humic and carboxylic acids formed during the biodegradation of plant litter. The structure features of soil profiles associated with variable, but high rates of downward filtering of these aggressive acids in landscapes with seasonal humidity. We experimentally simulated these conditions for studying a wide range of mobility of trace elements in soil horizons [Alekhin and Kostyukova, 2002]. Experimental methodsreceptions at carrying out of these experiences were similar to what are used at chromatographic differentiation into columns with processing of results by a method of concentration curves [Alekhin and Lakshtanov, 2008; Lakshtanov and Alekhin, 2005]. Objects and methods. Soil and soil water samples were collected in Meshcherskaya lowland. Soil water was filtered through the filter with pore dimension of 0.2 micron. Four horizons of podzolic soil (humus (A), eluvial (E), illuvial ferruginous (Bf) and gley horizon transition from illuvial to the parent rock (BCg)) were used in experiment. Four columns which were tightly closed have been made of the selected material. At the first stage of the experiment through each column the distilled water was passed for research of migration of trace elements at its infiltration as analog of fresh meteoric precipitation through soil. Then through columns the distilled water with addition sodium azide (for suppression of ability to live of microorganisms of soils) was passed. The second stage of the experiment consisted in filtering through columns of the solution close on properties soil, with initially high content of humic and fulvic acids (with the addition of sodium azide). At the third stage in this solution, related soil, carboxylic acids: acetic, lemon and oxalic in a ratio 1: 0,05: 0,003 were added. Such concentration ratio of acids was chosen because it close to a natural ratio in water extracts from soils and acidity (pH = 4,2) the solution is comparable to natural size [Hees et.al., 1996]. Addition of these acids in filtrant allowed to make active process of migration of elements of soil layers, remaining within the limits of experiment approach to natural process. At the fourth stage of the experiment polyelement standard ICP-MS-68B Solution A (HighPurity Standards) was added to a solution with humic and carboxylic acids. The standard solution contains elements (Al, As, Ba, Be, Bi, B, Cd, Ca, Ce, Cs, Cr, Co, Cu, Dy, Er, Eu, Gd, Ga, Ho, In, Fe, La, Pb, Li, Lu, Mg, Mn, Nd, Ni, P, K, Pr, Re, Rb, Sm, Sc, Se, Na, Sr, Tb, Tl, Th, Tm, U, V, Yb, Y, Zn) with concentration 100,0 ± 0,5 mg/l. The standard was dissolved so that initial concentrations of all elements in a solution were 1 mg/l (pH = 3,5). Addition of microelements given the chance to study method of adsorption curves of elements by columnar material (soil), and also to compare concentration of trace elements in filtrates. Filtrates were selected time a day during all experiment. In parallel with sampling potentiometry (pH, pNa, pCa) for control of change of indicators were spent. Each following stage began after an establishment in system of stable indicators. The mass spectrometer of the high permission with is inductive-connected plasma ELEMENT of 2 Thermo Finnigan was applied to definition of concentration of trace elements in filtrates.