Investigation into the elemental composition of sapropel from Lake Kirek (West Siberia) by SR XFA technique

Abstract

The synchrotron radiation X-ray fluorescence analysis (SRXFA) technique was applied for scanning two sapropel cores: 6.2 m (coordinates of boring 56°11′93″ N, 84°23′22″ E) and 3.6 m (56°10′93″ N, 84°22′94″ E), obtained at a depth of 5 and 7 m, respectively, in Lake Kirek (southern part of Tomsk oblast, West Siberia). Based on variations in the content of eight chemical elements in stratified core horizons, the geochemical types of the sapropels and their prevalence were established. In the sediment of the 6.2-m core within the overall boundaries of the Holocene, low-ferric calcareous sapropel dominates, the geochemical characteristic of which is presented by the average values of 13 chemical elements in the strata grouped by the main climatic periods of the Holocene. Organic-ferrous sapropel 90 cm in depth was uncovered in the 3.6-m core in the range 215–305 cm (age of 7-4 ka). For the other core horizons, the deposit is represented by calcareous sapropel, but with higher contents of iron in comparison with the first type. The geochemical differentiation of these two types of sapropels (in 3.6-m core) is characterized by average contents of 31 chemical elements. The consistency of the compositions and concentrations of chemical elements in sapropels in the Holocene section of the deposits is evidence of the identical formation conditions for these types of sapropel.