Distribution of Potential Pollutants in Water and Bottom Sediments of Natural and Technogenic Limnosystems: A Case Study of the Baraba Lowland, Russia

Abstract

Regional background concentrations of 10 priority potential pollutants (Hg, Cd, Zn, Pb, Cu, Cr, Co, Ni, Fe, and Mn) were established for the first time in the water and bottom sediments of 18 lakes in the Central Baraba Lowland. Comparison of natural and technogenic limnosystems using three normalization standards (regional background concentrations (RBC), upper continental crust (UCC), and Post-Archean Australian shale (PAAS)) showed that the choice of reference fundamentally influences enrichment/depletion interpretations. Concentration coefficients for Mg, Si, Sr, Pb, and Mn are standard-independent (“stable”), whereas those for Cd, Sb, Cr, Cu, and Hg are standard-dependent (“unstable”) and require explicit specification of the reference. Despite similar bulk sediment geochemistry, spheroidal and irregular Si–Fe slag particles found in technogenic limnosystems provide direct mineralogical evidence of aerotechnogenic input. Alkaline, bicarbonate-sodium waters act as an effective geochemical barrier, sequestering elements in the solid phase and supporting self-purification. Sapropels meet Class I of State Standard GOST R 54000-2010 for all elements except Zn (Class II), confirming their resource potential under proper quality control. Future work should expand the list of analytics and include all components (water, sediments, biota, and catchment soils) to build a comprehensive model of limnosystem functioning under anthropogenic load.