Сomparative characteristics of the content of heavy metals in the bottom sediments of the Kaliningrad sector of the Baltic sea and Eckernförde bay

Introduction

The article analyzes the data on the content of chemical elements in bottom sediments of different parts of the southern Baltic, obtained as a result of 35 and 37 cruises of the R / V Akademik Nikolai Strakhov in the Gdansk basin and data from the German sector of the Baltic Sea obtained in the Eckernförde Bay. Data from the German sector were provided by the Center for Oceanological Research GEOMAR (Kiel), were obtained as a result of sampling in the Boknis Eck station in March 2016. Studies have shown that the concentration of metals in sediments begins to increase, presumably due to pollution, at depths of 10-16 cm. Comparing the data obtained in the Kaliningrad sector and in the Eckernförde Bay, there is a difference in the distribution of almost all elements, this difference is explained not only different anthropogenic load, but also the hydrochemical conditions of deep-sea waters in this area and sedimentation. Comparing the data, the largest difference in results was characteristic of Zn concentrations. In Eckernförde Bay, the average values ​​were 193 μg / g, and the maximum was 216 μg / g, while the average value for 4 columns in the Kaliningrad sector was 112 μg / g. Despite the fact that the sampling took place in the immediate vicinity of the D-6 and D-33 oil platforms, the analysis of the samples did not reveal any consequences of the anthropogenic impact of the platforms.

Figure 1. Location of sampling points in the South-Eastern part of the Baltic Sea (columns 37056, 37057, 35097, 35084)
Figure 1. Location of sampling points in the South-Eastern part of the Baltic Sea (columns 37056, 37057, 35097, 35084)
Figure 2. Location of the station (Boknis Eck) at the entrance to the Eckernförde Bay (Zhao, Schlundt, Booge, Bange, 2020)
Figure 2. Location of the station (Boknis Eck) at the entrance to the Eckernförde Bay (Zhao, Schlundt, Booge, Bange, 2020)

Keywords

bottom sediments, heavy metals, pollution, Baltic sea

Research question

The purpose of the work is to analyze the content of chemical elements in bottom sediments of various waters of the Baltic Sea, to determine the reasons associated with the regional characteristics of the anthropogenic factor affecting the change in the content of heavy metals (HM) and other chemical elements in bottom sediments, taking into account the specifics of pre-industrial concentrations of chemical elements and the nature of the formation of the Baltic Sea. To achieve the set goals, the following tasks were formulated:

  1. Describe the formation of the modern chemical composition of the Baltic Sea bottom sediments.
  2. To establish the features of anthropogenic impact on bottom sediments in different parts of the Baltic region.
  3. Analyze the concentrations of chemical elements in the bottom sediment columns of the Kaliningrad sector of the Baltic, Eckernförde Bay (Germany).
  4. To establish the reasons for the different distribution of chemical elements in the investigated bottom sediments.

Main method

The study used the quantitative characteristics of elements (Ni, Zn, Co, Cu, Cr, Pb, As) in bottom sediments of different parts of the southern Baltic. Data used on the content of elements in 4 columns of bottom sediments sampled in the Gdansk Basin on cruises 35 and 37 of the R / V Akademik Nikolay Strakhov, the maximum depth of the seabed sediments - 83 cm, bottom sediments were mainly represented by homogeneous, silty-pelitic silts. The content of elements in the studied soil samples was determined by atomic absorption analysis in the laboratory of the AO IO RAS. The data that was provided by the Center for Oceanological Research GEOMAR them. Helmholtz, (Kiel - GEOMAR) were obtained from sampling at Boknis Eck in March 2016 Samples were taken using Van Veen grab buckets and a Reineck sampler, data analysis was carried out in the Geomar laboratory using atomic emission spectroscopy (ICP-AES). When comparing the data, the largest difference in the results was characteristic for zinc concentrations.

Table 1- Average indicators for the content of anthropogenic elements in bottom sediments of the Kaliningrad sector, Eckernförde Bay and the Gulf of Finland

Table 1- Average indicators for the content of anthropogenic elements in bottom sediments of the Kaliningrad sector, Eckernförde Bay and the Gulf of Finland

Figure 3 Map of the disposal of chemical weapons after World War 2 (Chemical Warfare Agents 2021)
Figure 3 Map of the disposal of chemical weapons after World War 2 (Chemical Warfare Agents 2021)

 Main results

Analysis of the data for the Kaliningrad sector made it possible to establish that the concentrations of heavy metals have the following stratification. Ni, Cr, As, Pb have an increased concentration at horizons from 10 to 55 cm, within these limits are the maxima of the mentioned elements, the exception was the results of Cu and Zn, their increased concentrations were observed in the upper horizon from 5 to 13 cm. It is noteworthy that for the intervals from 65 to 81 cm, the concentrations of all heavy metals have a uniform stratification, with the exception of rare, single increases in concentrations in the intervals of 70-74 cm. that the sampling took place in close proximity to the D-6 and D-33 oil platforms, the analysis of the samples did not reveal any consequences of the anthropogenic impact of the platforms.

Regional zoning "north-south". For the northern part of the Baltic Sea, bottom sediments of the early stages of development are subject to active erosion. The acidic sulphide soils of Finland, sea silts formed in the Holocene are destroyed, and to a large extent the concentrations of metals with river runoff enter the Baltic Sea. The southern part of the Baltic Sea is represented by outcrops of sediments from the early stages of the development of the Baltic Sea. Increased distribution of levels of concentration of heavy metals in the surface deposits of industrial zones, especially where the industry developed first.

Figure 4. Average Zn distribution in Eckernförde Bay samples.
Figure 4. Average Zn distribution in Eckernförde Bay samples. 
Figure 5. Zn distribution in samples from the Kaliningrad sector 35097
Figure 5. Zn distribution in samples from the Kaliningrad sector 35097 

Main conclusion

Considering the sedimentation rate of 4 ± 2 mm / year (Grigoriev, Zhamoyda, Spiridonov, Sharapova, Sivkov, 2009) and based on the data obtained, the analysis did not reveal significant pollution of these sediments. The exception is high chromium concentrations (148.25 mg / kg average over 4 columns). Presumably, such concentrations of chromium are associated with dumping of chemical weapons and corrosion of sunken ships, since in the 20th century, chromium was actively used for the manufacture of firearms, hulls of submarines and sea vessels (Morshin and Nikish, 1974). The Kiel Canal (Nord Ostsee Kanal) is located in the bay, which connects the sea routes between the North Sea and the southern part of the Baltic Sea, and the Eider kanal was used on the territory of Schleswig-Holstein until the end of the 19th century. Despite the absence of large land-based sources of impact on the waters of the Baltic Sea, the main environmental problems for the Bay of Kiel and Eckernförde are the spread of blue-green algae and an increase in methane concentrations in coastal waters (Schmaljohann, Whiticar, Treude, Maltby 2018).

References

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Author

Nikolajs Filipenoks, masters student, Institute of Living Systems, Immanuel Kant Baltic Federal University, Kaliningrad, Russia  nikolajs.filipenoks@gmail.com

The author is grateful to the employee of the Department of Marine Biogeochemistry Research PD Dr. Florian Scholz and Geomar Marine Geosystems Research Unit for their data and research assistance.

The study was carried out with the financial support of the Russian Foundation for Basic Research and the Government of the Kaliningrad Region in the framework of the scientific project No. 19-45-390007r_a

Last modified: 2021-10-19
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