Contribution Of The Different Sources To The Formation Of Alluvial Sediments In The Selenga River Delta. (Eastern Siberia, Russia)

Abstract

Unraveling sources of sediment supply, their temporal and spatial variability is of key importance to determine origin of deposits and to explore the formation mechanism of Selenga Delta landscape units. From an environmental point of view this solution would help to identify the particle-bound pollution sources. We used geochemical fingerprinting (the FingerPro R package), which is a modern quantitative implementation of the method of sedimentary provenance analysis. The main aim was to recognize the main patterns of sediment and associated particle-bound pollutants transport and deposition within the delta. At the old floodplain from 55% to 90% of sediments were delivered from the eroded floodplain and terrace banks upstream and only about 10-15% originates from the remote basin sources. Sedimentary environment in the Khlystov Zaton reveals a greater variety than on the floodplains. 40% of sediments from the upper 5 cm-layer originated from the flood, taking place in 2013, and 30% were the product of floodplain and terraces banks erosion. Nevertheless, analysis of the fine-grained component of suspended sediment sets the material from eroded floodplain banks as the dominant source of accumulation within the delta. This means that the self-absorption is the leading process in the Selenga delta at the moment. Heavy metals and metalloids accumulates in the lower reaches of the Selenga on the floodplain surface, deltaic lakes and oxbows during high floods. Runoff decrease during floods can lead to the release of pollutants into the Lake Baikal.