Rocks, soils, water, plants, animals and man, all these are links in the biogeochemical chain of the chemical elements' migration in the biosphere which unites into a single whole all of the kingdoms of the living and the inanimate nature. As far as soils are concerned, they are the central link-the focal point of various bonds between the mineral and biological worlds. To learn how their chemical composition is formed and elements accumulated, which pass on into plants and water, is an important scientific and practical problem. Its solution will make it possible to determine the role of soils in maintaining the naturally determined flow of elements in the biosphere and in foiling the anthropological impact.

These problems are investigated by the Laboratory of Soils' Biogeochemistry of the Institute of Soils and Agricultural Chemistry of the RAS Siberian Branch. Its head A. Syso, Cand. Sc. (Biol.), informed us about their studies.

The studies of the territory of Western Siberia have confirmed that this is a complicated region from the point of view of biogeochemistry. There are vast areas with higher and lower natural contents of macro- and microelements in objects of the environment here. A region of boron salting was singled out earlier in the arid south of the forest-steppe and steppe zones on the low Barabyn, Kulunda and Ishym plains, where salty landscapes prevail. According to the latest studies, strontium, fluorine, iodine and bromine in excessive qualities can also enter the food chains here. Moreover, since it is there, where the forage grounds are mostly located, it can result in a number of the cattle endemics diseases. As far as the local population is concerned, it is threatened by increased levels of boron and bromine, which leads to grave problems with the gastrointestinal tract.

As for the Western Siberian taiga zone and Novosibirsk region, the situation is different there. Soils and water there contain very little unbound fluoride and iodine, and it is natural that their chronic deficit in man and animals leading to endocrine system and teeth disorders has been detected. The lack of these halogens in potable water is especialy alarming for the residents of big cities like Novosibirsk, Barnaul and some others, where because of the tough chemical water cleaning their concentration goes down to the critically low level. In the Ob River the levels of fluoride and iodine amount to correspondingly 600 and 10 mkg/1, and in tap water it does not exceed 250 and 3-4 mkg/1.

Most of phosphorus, arsenic, zinc, copper, cobalt, molybdenum, chrome and nickel have been detected in the regions gravitating towards the Western Siberian plain's mountain edge, rich in various kinds of ores. The soils' saturation with a toxic element like arsenic here often exceeds the maximum permissible concentrations accepted in Russia. At the same time most arsenic in the soil is present in a hardly soluble form so that plants can absorb not more than 1% of the element's gross contents. The situation seems to be the same with zinc, copper, cobalt, chromium and nickel. That's why even with their increased concentrations in soils the quantities entering the biogeochemical chains are often insufficient for the normal course of metabolic processes in plants, animals and man.

Studies prove that the appearance of such an "arsenic" province and the possible existence of other provinces similar to it (for instance, a molybdenum one) can be connected with the dispersion aureole of mineral ores in the southeast of Western Siberia. Soil-forming processes, which considerably modify the mobility of molybdenum and vanadium, also have an important part to play causing their excessive accumulation in plants and water and upsetting their ratio with other elements optimal for animals and man.

The gross reserves of iron and manganese in soils in the arid south of Western Siberia, and in Kulunda in particular, are not large and their mobility is low due to the medium's alkaline reaction. That is the reason why plants, animals and man can experience an acute deficit in these elements. As for the territories with a

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humid climate and soils with acid reaction, it concerns mainly the Western Siberia taiga zone, there, on the contrary, is a high mobility of iron and manganese in soil and their excessive levels in living beings.

All of the above-mentioned concerns the formation of a naturally conditioned pool of macro- and microelements in food chains. However, today the anthropogenic influence on the environment has lead to qualitative and quantitative changes in the chemical substances' migration in the biosphere. Therefore, the ratios between elements have been upset and the percentage of toxicants has risen. And this has had a negative impact on plants, animals and man. As a result, a deterioration of the agricultural products' mineral value, a decrease in the animals' productivity and in their reproduction have been registered in Western Siberia. As regards the population of the Novosibirsk Region, such diseases as endemic wen, sugar diabetes, sexual underdevelopment of children and youngsters and anemia are on the increase.

The investigations of the Western Siberian territories carried out by the laboratory staff have revealed that the anthropogenic impact on the environment as a whole has led to negative changes in the elements' contents in parts of the food chain. At the same time, dangerous pollution of soils with heavy metal and other harmful substances is locally traced. A deficit of phosphorus, sulfur, zinc, copper, cobalt and iodine has increased in arable areas, where macro- and micro-fertilizers are practically not used today. Against the background of this deficit growing surpluses of other elements are being registered. In some regions the salting of the drained low bogs, irrigation of chernozems with mineralized water, chemical melioration of salty lakes with phosphogypsum and pollution with heating plants' wastes have led to mounting food pollution with boron, molybdenum, fluoride, bromine, strontium as well as chrome and nickel. Although so far this process has not become dangerous or widespread.

On the territories of industrial centers, where local hotbeds of a heavy technogenic soil pollution have been detected, the degree of damage done to various elements of the environment depends on the concentration and chemical properties of the polluting elements, the soils' ability to inactivate them as well as on the plants' biological peculiarities. For instance, studies in Novosibirsk have revealed that arsenic, zinc, copper, molybdenum and lead enter the city environment mainly in slow-moving form whereas most of the soils there possess a high buffer ability to heavy metals. This means that the passage of pollutants from soil to plants is rather limited, besides the latter are capable of regulating the uptake of the elements they absorb. The data of the accumulation of arsenic in plants is a glaring case in point. Even when its concentrations in soil exceed 40 mg/kg (twice the maximum permissible concentration) the accumulation of this toxic element in vegetable products were up to the norm. It is the same with other elements except cadmium which can enter plants in excessive amounts even when its gross concentration in soil does not exceed the norm.

The results of the said research has provided the basis for the biogeochemical zoning of the Novosibirsk Region. Later on such zoning will be carried out for the whole south of Western Siberia.

Nauka v Sibiri (Science in Siberia), 2001

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