Featuresof the elemental composition of lake waters and macrophytes in thermokarstsubarctic ecosystems of Western Siberia

With increasing anthropogenic impact on the environment, including local contaminationas a result of human activities as well as global pollution through longrangeatmospheric transport, the question of accumulation trace elements on all levelsof aquatic ecosystems is becoming increasingly important. Thermokarst lakes of thenorthern regions of Western Siberia as objects of hydrochemical and biogeochemicalresearches remained, up to present time, insufficiently studied: there are only fragmentarydata on the hydrochemical composition of lake water and the biogeochemical processesoccurring in the thermokarst lakes. In this work, we studied thermokarst lakeswith coasts composed of peat sphagnum moss, peat sediments and detritus. As a biologicalmodel we selected the plant macrophyte Menyanthes trifoliata L. The generaldynamics of chemical elements concentrations in Menyanthes trifoliata L. in all fourecosystems are very similar. However, there are some differences, in plants growing inthe intertidal zone of thermokarst lakes most in comparison with other ecosystems, withrespect to concentrations of K, Sb, Pb and Ba. Plants growing in the old khasyrei aremostly enriched by major elements such as Mg and Ca and trace elements Mn, Co, Rb,Sr, Cs. Minimumal concentrations in plants of all ecosystems are typical for rare earthelements, immobile in fresh waters and biologically unavailable for plants, as wellas for three- and tetravalent hydrolysates. In the course of work were calculated thecoefficients of biological accumulation of chemical elements in Menyanthes trifoliataL. relative to water (Kb) for all the four stages of lake ecosystems development. Highvalues of Kb are exhibited by macronutrients which are necessary for plants life cycle(K, Mg, Na); these values vary dependent on the stage of lake development. In particularwith the lake maturation we observe the decrease of Kb value for Mg, but also theincreases the Kb of Na. The elements actively accumulating in Menyanthes trifoliata L.are Rb, Sr, Ba, Pb, which may be partially linked to possible contamination of the waterreservoir (Pb). Data on the number of other elements obtained in the course of the workare in agreement to previously published works by other authors (i.e., high content ofMn, Pb, and low content of Cr). Another heavy metals strongly accumulating in grassMenyanthes trifoliata L. are Pb, Zn, Sr, Co, which may indicate various sources of longrangeatmospheric pollution or local lexivation from thawing peat.

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