Antsibor, Julia B. (2009) Background Levels of Heavy Metals and PAHs in Permafrost Sediments of the Lena Delta, Siberia. (Master thesis), Saint Petersburg State University ; University of Bremen, Saint Petersburg, Russia ; Bremen, 55 pp.

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Abstract

The studies of pollutants such as heavy metals and hydrocarbons and their influence on natural ecosystems draw attention in recent decades due to intensive industry development. The northern areas are in particular sensitive to influence of contaminants since they have low recovery potential. The Lena River Delta belongs to the Arctic regions which are quite far from industrial centers and therefore least of all subjected to human impact. However this area located in the permafrost area is characterized by specific environment that makes this ecosystem more vulnerable to any human activity.
The present study represents the first attempt to determine background levels of heavy metals and polycyclic aromatic hydrocarbons (PAHs) for the site of interest. Here the results of physical and chemical investigations of the core sample are proposed. The core with length 540 cm was formed during Quaternary period and presented by alternation of silt sand with the rest of plants. It was recovered while joint Russian-German expedition in 2007. Study of selected samples was based on the Laboratory of the Institute of Soils science, Hamburg University (Hamburg, Germany).
As part of the laboratory study we determined grading of soil, water content, soil acidity, organic matter content, total heavy metals (Zn, Cd, Pb, Ni) and As content and sum composition of PAHs as well. On basis of the obtained results on the core it was found out that heavy metals were accumulated in the horizons composed of silt fractions whereas its minimal content was detected in horizons of fine-grained sand.
Overall the heavy metals concentrations were higher in the bottom of the profile in comparison with overlying layers. The behavior of As within the profile was in the opposite way. The maximum was observed on 12-15 cm depth then within the all profile As content was not varied a lot. The correlation analysis showed the significant positive relation between the following metals: Zn and Ni, Zn and Cd, Cd and Pb.
Comparative analysis of findings with crustal abundance (Vinogradov, 1957) showed that Zn and Ni lateral concentrations were less than the average grades of these elements in the earth crust. Lead content was less as well in comparison with the approximate permissible concentration for uncontaminated soils (Isaev, 1998). The values of Cd were higher than crustal abundance only in the bottom of profile. The crustal abundance for As was found to be less than the value within the all profile.
The PAHs analysis showed insignificant amounts of hydrocarbons within the profile and their distribution is probably due to microbiological processes occurring in the most recently sedimented material.
The assessment of natural geochemical background levels is very important for the territories which are not strongly influenced by human activity since under increasing human impact it is helpful to know the initial environmental conditions to monitor the further changes.
The data obtained in this study can be used as the first step to assess the sediment and soil background levels in the Lena River Delta. Additional investigations of relatively undisturbed sediments in the Lena River Delta may help to understand the processes affected heavy metals and PAH migration and accumulation in permafrost soils and sediments as well as to gain insight into the peculiarities of their redistribution in the center and in the rims of sediment polygons in permafrost.

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