Geochemical differentiation of iodine and selenium in landscapes: first results on example of the Bryansk region

Introduction. A study of iodine and selenium in landscapes of the Bryansk region was started to estimate contribution of the natural background of these elements essential for thyroid gland [Arthur et al., 1999; Ermakov, 2004], to spatial distribution of thyroid diseases after contamination of the area by the Chernobyl radioiodine isotopes. The Bryansk region is noted for a variety of the soil-forming rocks and soils [Prosyannikov, 2002], a pronounced deficiency of iodine in local diets [Proshin, Doroshchenko, 2005] which contributed to the risk of thyroid cancer in the region contaminated due to the Chernobyl accident [Shakhtarin et al., 2003]. At the same time an increase of the thyroid cancer in areas with different radiogenic load is comparable that could be a result of different reaction to radioiodine impact due to variation of stable iodine and selenium background. The main objective of experimental work presented in this paper was to evaluate natural variation of selenium and iodine concentration in the components of the local food chain noted for I and Se sink (the soils) and transfer (drinking waters, plants). Study region and methods Selection of the test sites and sampling. Landscapes and soils of the Bryansk region are characterized by different geochemical features. Figure 1 presents a schematic map of landscapes different in soil and vegetation cover and in the dominating pH-Eh types of water migration according to Perelman (1975).