Saturday, 15 July 2006

Metals-Organic Interactions and Their Ecological Significance.Symposium 2.5A.

Galina V. Motuzova Jr., Moscow State Univ, Faculty of Soil Science, Leninskie gory, Mendeleeva ul., Moscow, 119899, Russia

">   face="Symbol">³³ between metals and organic substances may be referred to the most important processes in soil. They make it possible to determine the chemical status of natural, agricultural and technogenic-altered landscapes. Under study were Leptosol in the taiga zone of Russia. The fractionation helped determining Cu, Zn, Ni in the composition of compounds with the organic matter of the soil solid phase as well as their compounds in differently charged fractions of the liquid phase in soils. The research was performed to estimate the intensity of metal microbiological mobilization in polluted soils and to study regularities of changes in the above indices and their effect on migration of metals in natural and technogenic-altered landscapes. The organic matter of the soil solid phases is responsible for metal fixation in soil. But the share of these compounds is frequently rather small, averaging about 10% of the total content in soil. Due to soil pollution with metals the amount of their compounds with the organic matter becomes increasing and can be dominating in definite cases. The organic matter is partially destructed under the influence of metals. This is testified by narrowing the Cha/Cfa ratio. Parallel with the formation of such compounds the opposite process of their destruction is proceeding in soils. The microbiological community is especially decisive in this process. For instance, some species of microscopic fungi enable to destroy the compounds of metals with the organic substance in litters of polluted Leptosol. The growth of fungi population in the course of their succession is accompanied by increasing the content of mobile metal compounds at the expense of those firmly fixed by the organic matter. Thus, fixation-mobilization, formation-destruction of compounds between metals and the organic matter may be considered as two opposite processes inherent to the dynamic soil system. No fewer dynamics is the system of compounds between metals and the organic matter of the soil liquid phase. The solutions in the forest soils are rich in different organic acids, being prevailed by complexes of metals with organic ligands. In polluted soils the metal ions can be served as an additional source of soil acidity not only owing to their hydrolysis. The other reason is the complex-formation of metals with organic ligands and hence the release of proton. The dependence between the indices of these processes has been quantitatively determined. The metal-organic complexes in solutions of the forest soils have a negative or zero charge, that is why the metal absorption by soil particles is decreasing but their migration become increased throughout the soil profile. So, ecological functions of soil are highly affected by interaction of metals with the soil organic matter. Frequently the metal fixation by organic substances is regarded as a mechanism responsible for the protective capability of soil against metals. However, entering into the soil the metals can destruct the organic matter and form with it the compounds, which are more mobile than initial ones. One of reason of local pollution of ground waters in the environs of a Cu-Ni enterprise in Kola peninsula is a higher mobility of metals-organic complexes. >*CJ mH  CJ H*mH CJ mH  

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