Home – Home – Jornals – Chemistry for Sustainable Development 2022 number 2

Concentrations of organochlorine compounds (OCs) were determined, and comparative analysis of OCs in the bottom sediments of the Chernaya river, small lakes of the Baydar valley, the Sevastopol Bay and the Chernorechensky reservoir, sampled in 2008 and 2019-2020, was carried out. A noticeable difference in the levels of pollution with OCs in the river, lakes and the bay was detected. This concerns mainly such OCs as polychlorinated biphenyls (PCB), the content of which in sediments of the studied areas varied within a wide range - from 0.5 in lakes to 900 ng/g dry mass in the Sevastopol bay. Increased anthropogenic pressure on the river water area in the region of Baydar valley and in the estuary area has led to the formation of zones with the local maxima of the concentrations of PCB and organochlorine pesticides (1,1,1-trichloro-2,2-bis(chlorophenylethane), DDT) in the bottom sediments of the Chernaya river. In the Baydar valley, the sediments in lakes were on average less contaminated than river sediments, which is due to the isolation of lake ecosystems; they may be classified as non-polluted and weakly polluted. The maximal OCs concentrations were detected in the Sevastopol Bay. The ratio of DDT metabolites in the composition of organochlorine pesticides depended on redox conditions in bottom sediments: under anaerobic conditions of the Sevastopol Bay, DDT was transformed into DDD (1,1-dichloro-2,2-bis(4-chlorophenyl)ethane), under aerobic conditions in the river sediment - into DDE (1,1-dichloro-2,2-bis-(4-chlorophenyl)ethylene). Reconstruction of sedimentation geochronology using radiotracer methods shows that the variability of OCs content at different depths of fresh-water sediments depended on the temporally varying amounts of OCs income into the water areas but not on the natural conditions of sediment formation. According to estimates, at present, the runoff from the Chernaya river contributes not more than 14 % ∑DDT and 4 % ∑6PCB into the bottom sediments of the Sevastopol Bay.