Geochemistry of trace elements in boreal seasonally stratified lake: control of colloidal iron and organic matter

摘要: We have studied colloidal distribution and size fractionation of major and trace elements in boreal strongly stratified lake of Arkhangelsk region (Maselgskoe lake of the Kenozersky natl. park 20 m depth) during 4 years in winter (glacial) periods, summer period and spring and autumn overturn. In-situ dialysis (1 kDa, 50 kDa) and frontal filtration and ultrafiltration were used to assess organic carbon and trace element concentrations at different depths. There are three groups of elements according to their concentration depth profile and affinity to colloidal fraction: those exhibiting little variation of concentration with depth (most monovalent and divalent elements and anions), those demonstrating strong increase in the bottom horizons with weak (Si, Mn, Ba...) or significant (Fe, REEs) proportion of colloidal forms.In all samples, large colloidal forms (10 kDa–0.22 µm) of iron, organic carbon, trivalent and tetravalent …