Evaluation of the contamination level of sea bottom sediments on the Crimean coast of the Black and Azov seas

Within the framework of the 83-rd cruise of the research vessel "Professor Vodyanitsky" (January-February 2016) a coastal area of the Crimea was investigated. The studied regions – water space of the Black and Azov Seas and pre-strait-area of the Kerch Strait - have varying degrees of the anthropogenic load. The aim of the work was to study the content of chloroform-extractable substances (CES), oil hydrocarbons (OH) and heavy metals (HM) in the sediments of the Azov-Black Sea basin including the areas of the north-western shelf of the southern coast of the Crimea, the Kerch Strait and the south-western part of the Azov Sea. Samples were obtained at 21stations using an automatic dredge. In the Black Sea, bottom sediment sampling points were located at the depth from 24 to 83 m, with the exception of a deep-sea station (1040 m). At the stations located in the Azov Sea the depth did not exceed 9 - 18 m. In the prepared samples the total amount of CES was determined by gravimetric method, the content of OH was determined by the method of infrared spectrometry using spectrophotometer SPM-1201, the total content of metals As, Cr, Co, Ni, Pb, Zn, V, Sr, and metals oxides TiO2, MnO, Fe2O3 using XRF spectrometer "Max Spectroscan-G». All the results for CES and OH concentrations were counted per 100 g of air-dried sediment (air.-dry.b.s.). According to the received data CES content in the sediments of the Black Sea ranges from 10 to 110 mg/100 g air.-dry.b.s. At the most stations OH concentration was in line with the trace values (less than 5 mg / 100 g) - from 1.7 to 10 mg / 100 g. In the Sea of Azov these figures were slightly higher and accounted for CES - from 107 to 187 mg /100 g, which corresponds to level III pollution, while OH - were in the same range as those in the Black sea (from 6.9 to 10.2 mg / 100 g). At the most stations in the Azov Sea the content of HM exceeded values obtained in the Black Sea. Now (2016) in the open Crimean coast bottom sediments of the Black Sea have properties typical for marine sediments of the studied area. There is an upward trend in the content of chloroform-extracted substances in the Black Sea region, but the sediments are not contaminated with oil products. Taking into account the physical-chemical characteristics of marine sediments, it can be stated that the condition the studied area as a whole is safe.