Elemental composition of soils and bottom sediments in streams of the eastern macroslope of the Subpolar Urals

Abstract

A study is made of the lead, zinc, copper, manganese, chromium, nickel and iron distribution patterns in soils and bottom sediments of streams flowing on the eastern macroslope of the Subpolar Urals. Results were subjected to a statistical processing to show a wide variation in content levels of metals due to a set of lithological and landscape-geochemical factors. The study revealed a correlation of anomalously high concentrations in soils with occurrence zones of ore mineral resources. Particular attention is paid to the lateral differentiation of lead. It is shown that its accumulation occurs in accumulative landscapes of river valleys, and its increased content is observed in bottom sediments during deposition on the sorption barrier. It is found that formation of bottom sediments showing increased contents of metals is associated with sedimentation characteristics at the time when the flow velocity of rivers decreases at the transition from mountain landscapes to lowland landscapes. The accmulation of elements in different components of migration series is analyzed to reveal regular differences in elemental composition of soils of middle- and low-mountain, low-mountain/ piedmont and submontane-lowland landscapes and to permit the description of the background geochemical associations. Regional percent abundances are calculated and compared with results obtained for neighboring areas of the West Siberian Plain. The postulate concerning the determining role of the surrounding mountains in the formation of the trace element composition of soils in Western Siberia. A deficit of copper and zinc content in bottom sediments is pointed out. It is concluded that dissolved forms are dominant in the aquatic transport of heavy metals.