Content and distribution of halogens in soil profile of natural and man-made ecosistems in the south of Western Siberia

The study showed that grey wooded soils in various areas in the south of West Siberia contained approximately similar amounts of total and water-extractable fluoride (230280 and 1 mg/kg soil)and iodine (1.4-3.0 and 0.2-0.3mg/kg soil, respectively), falling within the range typical for the zonal soils of the territory. The chloride concentration was found to vary notably, from 10-11mg/kg in the Novosibirsk Near-Ob area, up to 40-50 mg/kg in soils of the Vasyugan and Barabinsk plains. The profile distribution of the halogens was mainly determined by humus and silt content in different soil horizons, as well as by the chemical properties of the elements. Chloride was found to display a relatively even profile distribution, independent of its absolute content. Content of halogens and regularities of their distribution were determined in the profile of virgin and arable grey forest soils of the south of Western Siberia. It was revealed that concentration of halogens in the soils in question was at the level typical for zonal soils of the region and did not exceed the maximum admissible concentration. It was shown that long-term application of fertilizers in agrocenoses lead to essential increase in content of soil of fluorine and chlorine; at the same time, distribution of chlorine in soil profile decreased with the depth, its maximum was in the upper horizon; as for chlorine, its distribution was uniform. The content of water-soluble iodine decreased greatly in the arable layer of soils of intensive agrocenoses but its total content did not change. The obtained results show that agricultural use of the previously undisturbed soils significantly affected their halogens' content. The long-term fertilization of agricultural soils resulted in statistically significant increase in fluoride and chloride concentrations; at the same time the concentration of water-extractable iodine in the ploughed layer of intensively used agrocoenoses decreased significantly. Reasonably balanced fertilization rates did not increase halogens' concentrations up to levels toxic for plants. Fluoride, added into soil with fertilizers, accumulated mostly in the topsoil layer, decreasing significantly down the soil profile. Chloride distribution along the soil profile, being rather even, did not depend on the rate of chloride input with fertilizers.

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