We present the results of investigation of the contents of metals (As, Cr, Co, Cu, Ni, Pb, Zn, V, Sr, Mn, Ti, and Fe) in the bottom sediments of the Balaklava Bay (Black Sea) carried out in July 2005. It is shown that the pollution of the bottom sediments with metals has a polyelemental character. We establish the specific features of changes in the contents of the analyzed elements and localize the sources of their appearance in the ecosystem. On the basis of the results of evaluation of the intensity of technogenic action upon the marine medium, we determine a group of toxic elements (As, Cr, Cu, Pb, and Zn) accumulated in the bottom sediments of the bay in amounts significantly exceeding the background values typical of sediments of the Black Sea shelf. The comparative analysis of the degrees of pollution of the bay and some other coastal water areas with metals is performed.The accumulation of toxic metals in bottom sediments is realized as a result of the gravitational sedimentation of suspended substances, sorption processes on the water-sediment interface, and biogenic sedimentation. Thus, bottom sediments reflect, in a certain sense, the processes running in the water column. The bottom sediments also serve as the habitat of benthic organisms, the state of development of which characterizes the aquatic ecosystem.By analyzing the contents of metals in the bottom sediments of various parts of the water area, one can estimate the level of pollution, determine the regions with different levels of anthropogenic loading, and establish the characteristic features of toxic metals depending on the natural geochemical processes and anthropogenic influence.Among the semiclosed water areas of the Sevastopol region, the Balaklava Bay occupies a special place due to its geographic location, morphometry, landscape and geochemical characteristics, and the character of nature management. The bay is located in the south part of the Crimean Peninsula between Cape Fiolent and Cape Aiya. This is a narrow (up to 240 m) estuary-type basin oriented in the meridional direction with high steep indented coasts 1.4 km in length and 4-34 m in depth. The area of the water surface is equal to 236,000 m 2 , the volume of water masses accumulated in the bay is 2,840,000 m 3 . Its mean depth is equal to 12.5 m. According to the bottom morphometry and configuration of the coasts, the water area of the bay can be split into the shallow-water part at the head of the bay, the central part, the south deep-water expansion, and the elbowed narrowness connecting the last two parts [1,2]. The head of the bay is supplied by the seasonal water flow of the Balaklavka River. In the dry season of the year, its discharge is equal to 196.9 ⋅ 10 3 m 3 /yr (according to the data obtained by Terekhin in 1991; cited according to [3]).
The purpose of the paper consists in studying the pollution level, and the character of spatial distribution of microelements and trace metals, the chlorophorm-extractable substances and petroleum hydrocarbons and in evaluating the features of their accumulation in the upper layer of bottom sediments in the Balaklava Bay depending on the natural and anthropogenic sources of pollutants. Methods and Results. The samples were taken from the bottom sediments upper layer (0-5 cm) in the Balaklava Bay by the Peterson grabber in February, 2015. Location of the sampling stations was chosen proceeding from the features of the bay morphometry, hydrological and hydrochemical water structure, pollution sources and the character of the sedimentation processes. The samples were selected, preprocessed and analyzed by the standard methods according to the regulatory documents. Some changes in relation between the clay fractions and the gravel material composition were revealed. The correlation dependence between the contents of chlorophorm-extractable substances and petroleum hydrocarbons was calculated. The features of spatial distribution of the metals' content depending on the natural geochemical processes in the bottom sediments are revealed. The regions subjected to the most intensive anthropogenic load within the region under study are distinguished. Conclusions. The content of clay material in all the samples taken in the Balaklava Bay on the average increased from 58.2 to 65.9 % and its maximum values are still concentrated in the western and northwestern parts of the water area under study. During last ten years, growth of the portion of a fine-grained material in the bottom fractions has been noted; at that the places where it accumulats are located in the areas of intense anthropogenic activity. The chlorophorm-extractable substances concentration in the Balaklava Bay bottom sediments varied within a wide range. On the whole, in course of the investigated period their content decreased, whereas the petroleum hydrocarbons concentration remained unchanged. It is found that pollution of the bottom sediments by metals is of a polyelemental nature and is characterized primarily by such metals as Pb, Cr, Zn, Cu and Sr. The increased microelements concentrations are observed in the northeastern and central parts of the water area, whereas the decreased metal concentrationsin its northwestern and eastern parts.
The physicochemical characteristics of the sediments of Balaklava bay: granulometric composition and fractional composition content of organic and inorganic carbon are considered. The spatial distribution of the main factions of particle size distribution and content of organic carbon (TOC) and calcium carbonate (CaCO 3 ) are investigated. The relationship between the organic and inorganic carbon and particle size distribution of sediments are analyzed. The main formation factors of the sediments from Balaklava bay are hightlighted. The results of the performed investigations have shown that the bottom deposits in the Balaklava Bay are represented mainly by silts and in some areas the gravel and sandy materials are interspersed. On average, for all the stations the fine-dispersed fraction content makes up 61%. The coarse-dispersed material is concentrated near the coast, and at the bay exit; the increased content of the sand fraction is typical for the central part of the water area. The calcium carbonate content in the Balaklava Bay varies within 18.32-82.95 %; its average value constitutes 40.06%. Its maximum concentrations are in the coastal parts of the bay. The highest correlation between the inorganic carbon content and the granulometric composition in the samples is observed in the coarse-dispersed material (fraction 2-1 mm). As for the fine-dispersed material, the sandy and alevrite-pelite silts are characterized by the inverse relation: from 0.4 -for the fraction 0.25-0.1 mm up to 0.6 for the fraction lower than 0.05 mm. The organic carbon content varies from 0.66 to 4.74%; the average value is 2.37 %. The presence of the increased values in the central part of the bay can be explained by "weak" water exchange formed by minimum wind and wave effect and insignificant eddy formations. Introduction. Coastal areas have always been an object of active human activity. It has contributed to formation of specific ecosystems which now constitute a part of the total ecosystem of the Black Sea. Study of sediments, their physical and chemical features, as well as the processes taking place in the water -suspended matter -sediments system is an important part of the total system of the coastal waters monitoring.A distinctive feature of the bottom sediments of the Black Sea coastal area is a high rate of sedimentation. In contrast to the deep-sea part where the sedimentation rate is 0.15 -0.35 mm/year [1], this process in the coastal areas increases. According to [2] in the Crimea coastal regions where the determining factor is the abrasion processes, the sedimentation rate is 0.35 mm/year, in the Sevastopol Bay -2.4 mm/year and in the Danube estuarine zone -11.5 mm/year [3].
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