Geochemical indicators of technogenic pollution of bottom sediments of small rivers in an urbanized environment

Abstract

We have explored the possibility of using the geochemical characteristics of migration and accumulation of alkali metals (lithium, rubidium, and caesium) as the indicators of anthropogenic status of heavy metals in bottom sediments of small rivers of a technogenically disturbed (urbanized) environment. A study was made of the behavior of the above elements in bottom sediments of the rivers of Petrozavodsk (Republic of Karelia). The chemical composition of the sediments used in the study was determined with X-ray fluorescence spectrometer ARL ADVANT’X and mass spectrometer XSeries-2 ICP-MS; the content of organic matter in bottom sediments (from the LOI index) was estimated by the weighing method upon heating the samples under investigation to the temperature of 1100°C. As a result of the investigations, it was found that among the heavy metals, Co, Ni, Cu, Zn, Mo, Sb, W and Pb are of predominantly technogenic origin in river sediments, which Cr and Cs are of predominantly natural origin due to a high background of these elements in Quaternary formations of the study area. We determined a close association of the trace elements of technogenic status as well as of Li, Rb and Cs with content levels of iron-manganese formations and organic matter in river sediments, which does indicate a commonalty of the processes promoting their input into the urban water stream. It is established that the commonalty of accumulation of a number of heavy metals in bottom sediments with lithophylic elements (Li, Rb and Cs), due to the high chemical activity of these latter, makes it possible to use the geochemical characteristics of the alkali metals as the indicator of technogenic status of the main pollutants of the urban environment.