IODINE AND SELENIUM IN SOILS OF THE BRYANSK REGION (CASE STUDY OF THE TITOVKA RIVER BASIN)

Abstract

The vertical and lateral distribution of iodine and selenium in the soils on different types of parent material, i. e. loesslike loams and fluvioglacial sands and sandy loams, was studied within associated landscape-geochemical systems of the Titovka River basin (Bryansk region, Russia). It was found that the content of both elements in particular genetic horizons of the studied soils under the contrasting environment varies widely, namely I: 0,22-7,93 mg/kg, n = 93, and Se: 0,001-0,668 mg/kg, n = 93, airdry mass. Gray forest loamy soil on loesslike loams contains 2 times more iodine and almost 4 times more selenium than sodpodzolic sandy loam soil on binary deposits (1,67 / 0,81 mg/kg for I (p < 0,05); 0,453 / 0,120 mg/kg for Se (p < 0,05), respectively).This may be due to both the type of parent material and higher content of organic matter, and the lighter texture of gray forest soils. The content of iodine and selenium in bottom sediments of the Titovka River (0,59 and 0,36 mg/kg of airdry mass) is most comparable with the upper horizon of sodcarbonategley soil sampled a few meters from the sampling site of bottom sediments (I - 0,57 mg/kg; Se - 0,35 mg/kg of airdry mass). At the same time, the elements showed dissimilar differentiation in soil horizons, due to their affinity to geochemical barriers. Iodine is actively fixed on the alkaline-carbonate barrier and is mobile under reducing conditions, while selenium concentrates on the gleyic barrier and is mobile in an oxidizing environment. This should be taken into account when assessing the availability of these biologically significant chemical elements in soils and local food products, particularly in the areas exposed to radioactive isotopes of iodine.