Biogeosystem Technique

17-40

Authors: Vyacheslav S. Anisimov, Natalia I. Sanzharova, Rudolph M. Alexakhin

When studying the behaviour of radionuclides – fission products of nuclear fuel, released into natural ecosystems after the Chernobyl accident, significant differences were found in migration capacity of 137Cs global fallout and Chernobyl origin. This is because the radionuclide in the Chernobyl fallout, in contrast to the global, entered to the surface of the earth not only in water-soluble form, but also in the composition of particles of nuclear fuel and composite materials of different dispersion. On the territory of 30-km zone around Chernobyl NPP were allocated to 2 areas, which differ in the form of depositions of radionuclides. The first, which was called the "near" area (2-15 km from the emergency unit of the ChNPP), dominated by the fuel component (the coefficients of fractionation of the non-volatile 144Се and 90Sr to 137Cs ≥ 1). In the second zone, named "remote" (15-35 km from ChNPP), was dominated the condensation component (f144Се/137Cs and f90Sr/137Cs < 1). In "near" to the damaged reactor zone properties of 137Cs, 90Sr and 144Се are largely determined by its localization within fuel particles, which are transforming in turn under the influence, primarily, of air oxygen and water. Thus, the content in the soils of mobile 90Sr in 1987, was 26.8 % in the "near" zone (v. Krasnoe) and 45.7 % in the "remote" zone (v. Radin). This is 3.6 and 1.3 times less of the relative content of mobile 90Sr in 1990. By 1990 there was a complete transformation of a primary fuel particles, as indicated the data about: almost complete 144Ce extraction from soils by 1 N solution of hydrochloric acid in 1990; about the reduction of the quantity of unleacheable 137Cs in soil in 1988 and especially in 1990 compared to 1987; and the fact that there is huge increase in the relative content of mobile 90Sr in 1990 as compared to 1987 in the soils of "near" zone where was dominated the fuel component of fallout. Due to the transformation of the fuel particles already in 1988 the mobility in soil and, consequently, the availability for the root uptake by plants of 137Cs, which is incorporated within the transformed fuel matrix, was higher than the mobility of the radionuclide in the soil exchange complex. The content of exchangeable and mobile forms of 137Cs was relatively high in the first year after the accident (9.5-30.1 and 12.7-41.2 %, respectively) and then decreased according to the exponential law due process of irreversible fixation of radionuclide by soils: dC/dt=-bС, where C is the content of the corresponding form of the radionuclide in soil; b – coefficient of proportionality. Calculated for automorphous soils located in "near" to the reactor zone, half-reduction periods of relative content of exchangeable and mobile forms of 137Cs in soil was equal to 3.7 and 7.0 years, respectively, and for automorphous soils of the "remote" zone – 2.7 and 4.8 years. For hydromorphous soils of "near" zone the half-reduction periods of the relative content of exchangeable and mobile forms of 137Cs was 1.8 and 3.2 years, for "remote" zone soils – 1.4 and 1.9 years, respectively.

49-64

Authors: Fedor N. Lisetskii, Aleksandr N. Muntian, Ksenija V. Zholumskaya

Preconditions of formation of soil conservation farming systems and prospects of irrigation reclamation development in the context of active manifestations of water erosion (for example, strongly dissected the central part of the Republic of Moldova) were investigated. It was found that over the past 20 years due to the intensification of agricultural production, the use of heavy equipment and the use of irrigation washability value of land increased by 1.5-2 times. It is shown that within the subsystem slope position-dynamic type agrolandscapes units have views of the landscape rather narrow bands. Their boundaries can be justified not only by the methods of landscape mapping, but also with the help of an integrated indicator of the potential duration of soil consumption, which includes stock assessment of soil resources and resource velocity forming and soil-destroying processes. This approach is complemented by the use of a series of micro-climatic irregularities card (first of all, heat and moisture) with quantitative gradation in the legend, and executed with the help of geographic information technologies allows for typing agroecological land and determine the most rational location for eco-restoration measures. As a result, the integrated application of biogeosystem-technology methods, adaptive-landscape approaches to land management in the face of strong manifestation of erosion there are new opportunities for controlling soil expenditure within the boundaries of landscape strips as the operating units contour-reclamation organization of agricultural landscapes to ensure the conditions of ecological rehabilitation of degraded land in the conservation mode, or annealing, as well as the creation of conditions for the conservation of biological diversity.

77-86

Authors: Evgeny V. Shein, Galina V. Kharitonova, Evgeny Yu. Milanovsky

Microaggregates in natural dispersed bodies – sustainable formations sizes less than 250 microns, in which the interparticle bonds are formed by organic matter, clay salts, diatomaceous spillways and some other substances. Organic matter in the microaggregates exist in inaccessible state in sustainable forms, and is not subjected to dehumification. But organic matter controls also the ability of soil to retain the structure in water; and the stability of the wet soil under external mechanical action. Dominant interactive forces between organic substances and the surface of mineral particles typically have sorption nature, hydrophobic interaction, ionic (or electrostatic nature) compound and van der Waals interactions. In saline soils and rocks microaggregates are presented in clay-salt formations. One of the possible types aggregate formation in saline soils may be the formation of quasicrystals. Packaging particle size and shape depend on the content of microaggregates and salts properties involved in their formation. The carbonates (calcite, dolomite) and ferruginous form clay-salt microaggregates. In many ways the formation of microaggregates in soils and other natural systems caused by bio-organic macromolecules produced by algae, particularly diatoms which uses a special strategy for connection with other particles (spines). A very promising direction is to study the formation of microaggregates under the influence of diatoms, which dominate in hydromorphic soils, moist habitats, river valleys. Numerous literature and own experimental data are discussed.