The joint influence of commercial preparation of humic substances and oils, oil-products and their individual components on Daphnia magna was studied. The presence of humic substances prevented, or at least reduced the transition of Daphnia magna into the superficial film in emulsions of oil products. It is shown that in some concentrations the preparation of humic substances weakens toxic effect of emulsions of oil-products and their saturated solutions on Daphnia.
The data obtained in experimental estimation of the attitude of several endemic amphipoda species toward the main environmental factors (temperature and the extent of water saturation with oxygen) are described. Thermoresistivity of amphipoda, stability to hypoxia, thermal preferences are described. In order to estimate the role of abiotic factors of environment in containment of endemics spreading off Lake Baikal, and to elucidate the role of mechanisms providing immiscibility phenomenon, the obtained data are compared with the expansion of the investigated species beyond Lake Baikal along the Angara
The composition of macroelements (Al, Si, P, Mn, Fe, S, Cl, etc.) and microelements (Cd, Pb, Zn, Cu, Ni, Co, Cr, etc.) in fir needles and in bushes of the Baikal biospheric reserve is considered for the purpose of revealing the reasons of shrinkage of fir forests. No high content of elements (including those indicating anthropogenic action, first of all from the Baikal Pulp and Paper Plant) was detected in fir needles and in the branches (with leaves) of bushes (except raspberries), which indicates the absence of a substantial arrival of inorganic elements of anthropogenic origin. The detected levels of the investigated chemical elements in fir needles cannot be the reason of degradation of fir forest within the reserve. Anomalous Cl content in raspberries is of unclear nature and requires further investigation.
The dependencies of daily photosynthetic productivity of the Siberian larch on total daily illumination, air temperature averaged over the photosynthesis period, soil temperature at the depth of 5 cm, and amount of moisture accumulated in the upper half-a-meter layer of soil are analyzed. Regular variations of this parameter are revealed. For larch under the conditions of optimal soil moistening, broad ranges of optimal air temperature and illumination are typical. The dependence on temperature is clearly expressed during cold seasons. The importance of these features in vital functions of plants is discussed.
A comparative estimation of the radiation status of water currents in the vicinity of Novosibirsk is presented. The data on U, Ra, Th, K content of bottom sediments, soils and rocks are listed. The distribution and concentration levels of natural long-living radionuclids in river-bed sediments in the territories which are the purest from the viewpoint of possible man-made pollution (basin of the Berd
The model for many-year dynamics of agroclimatic potential of territories is presented. The model describes agroecosystem dynamics with theoretically highest accuracy. Progress of phenological development of plants; monthly (including the winter) dynamics of soil humidity; crop formation and its bulk; many-year trends of average monthly air temperature, precipitation and anthropogenically influenced fertility of soils; dynamics of agroclimatic potential of territory were estimated simultaneously by numerically solving the inverse problem on the basis of many-year sets of actual wheat crops, long-term average monthly temperature and precipitation. The agricultural area of Siberia is considered as a case study. Information basis for a well-known Le Chatelier principle characterizing self-stabilization of agroecosystems and ecosystems has been revealed. Self-stabilization provides
The dependence of adsorption of Cu and Pb on their chemical nature, properties of soils and concentrations of the solutions applied is investigated. The mechanisms of the interaction of Cu and Pb ions with various soil ingredients are considered. It is shown that the adsorption of Cu and Pb by chestnut soils proceeds in agreement with Langmuir equation. The parameters of Langmuir equation are calculated.
It is demonstrated in small-allotment field experiments with unpolluted gray forest soils of Pribaikalia and the same soils polluted with water-soluble fluorides (6 MPC) that the pollution did not cause a decrease in the productivity of spring wheat; fluorine was accumulated only in straw. Investigations with 15N isotope revealed that pollution caused an increase in mineralization of the soil nitrogen and in gas losses; on the contrary, (re)immobilization decreased. This caused the formation of highly deficient total balance of nitrogen in soil. Efficiency of land improvement by peat and superphosphate at the background of NPK was exhibited by an increase in (re)immobilization and decrease in gas losses of nitrogen.
The data on the content of natural radioactive elements (U, Ra, Th, and K40), as well as technogenic Cs137 in soils, subsoil substrata and bottom sediments of the regions of closed lake hollows are presented. It is shown that under the conditions of internal-drainage regions uranium is accumulated at a number of geochemical barriers: evaporative, sorption, gley and hydrogen sulphide. The intensity of uranium migration depends on the chemical composition of superficial water.
VALERY M. DEMBITSKY1 and GENRICH A. TOLSTIKOV2 1Department of Pharmaceutical Chemistry and Natural Products, School of Pharmacy, The Hebrew University of Jerusalem, P. O. Box 12065, Jerusalem 91120 (Israel), E-mail: dvalery@cc.huji.ac.il 2Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Pr. Akademika Lavrentyeva 9, Novosibirsk 630090 (Russia), E-mail:
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Natural halogenated sesquiterpenes from marine organisms form a large group of natural compounds. The structures of more than 200 compounds are considered, and their biological activity is described.
