Heavy metals and the "Chernobyl trace" in the bottom sediments of the internal reservoir: The Gulf of Kaliningrad

Abstract

Introduction. The article contains the results of a study of environmental hazards and threats to public health from the accumulation of heavy metals (HM) and the activity of man-made and natural radionuclides (NRN) in the bottom sediments of the inner reservoir r - the Kaliningrad Bay at the turn of the XX-XXI centuries (1986-2019). The Consumption of polluted resources (seafood, bottom sediments as fertilizers, and mineral raw materials) can negatively affect residents’ health of not only this region. The problems are considered: 1) the mechanism and intensity of the long-term accumulation of Hg and other HMs, 2) the activity of the 137Cs isotope (“Chernobyl trace”) and NRN in comparison with the radiation state of the beach Sands in Latvia, 3) the biomedical threats from the factors considered. Results. The water’s closed area led to the role of the bay as a giant trap of sedimentary material and pollutants. Hg in the water reached dangerous concentrations of 0.15-0.6 mcg/l (MPC = 0.5 mcg/l). The accumulation of Hg in the bottom sediments of the Gulf estuary and Primorskaya Bay has reached a low level of pollution over 20 years (Norwegian criteria: from 50-90 to 155-252 mcg/kg) and has approached the safe limit - the target level (300 mcg/kg - the national, regional standard and Dutch lists of the pollutants). The Hg content also increased in the background (from 23 to 82 mcg/kg). The most dangerous foci of sanitary and toxicological hazard (Zc-t index (AgPbCoW) >6, up to 13) coincide with the borders of dangerous accumulation of the sum of HM (Zc(MnCrVNiCoAgZnPbSnW) >34, up to 61) and Hg (>100-150 mcg/kg). The initial activity of 137Cs in the Baltics decreased, Bq/kg: from 110 (beaches of Latvia) to 104 and 99 (bottom sediments; coasts of Lithuania, Kaliningrad region, and Poland). The specific activity of NRN in the bottom sediments of the Gulf (510-572 Bq/kg) is below the safe level (740 Bq/kg); handling them has no restrictions. Conclusions. An increase in the amount of Hg causes the danger. The trend requires research and monitoring, including Hg in seafood and biomonitoring.