Biogeochemical regioning problems and the biogeochemical selenium provinces in the former USSR.

Current trends in biogeochemical research in the former USSR are exemplified for the trace element selenium (Se). Vast regions of the former USSR are low in Se, giving rise to selenium deficiency diseases in animals and to Kaschin-Beck disease in humans, whereas isolated high-Se regions are comparatively rare. The Se content of plants depends on geological soil-type and secondary processes such as weathering and leaching. In general, a direct correlation between the Se content of feedstock and of the blood in animals is observed, whereas corresponding data for humans remain to be accumulated.