Integral chemical-ecological state evaluation of the inlets Kozmin and Ozero Vtoroe (Nakhodka Bay, Peter the Great Bay, Japan Sea)
Chemical-ecological state is evaluated for two secondary inlets of the Nakhodka Bay: Kozmin and Ozero Vtoroe. Data on their water temperature, salinity, biochemical oxygen demand (BOD), pH, alkalinity, content of chlorophyll a, organic matter, nutrients, oil products, detergents, polycyclic aromatic hydrocarbons (PAHs), phenols, and organochlorine pesticides (HCH and DDT) are presented. Heightened BOD and increased content of petroleum hydrocarbons, PAHs, phenols, and pesticides are found both in the water and bottom sediments of the inlets. In the water, the level of petroleum pollutants was 6 times higher than the maximum permissible concentration (MPC), the PAHs content was 10-100 MPC, the contents of phenols and organochlorine pesticides were 1.0-1.5 MPC and 1-2 MPC, respectively. The accumulated contents of these pollutants in the bottom sediments reached 1-9 MPC, and BOD was 20 % higher than the maximal permissible level that indicated an eutrophication process. The most extreme chemical parameters were observed in the north-eastern part of the Kozmin Bay where the dissolved oxygen content was reduced to 11.0-11.6 mg/l, BOD was heightened to 2.57-3.37 mg/l per 5 days, there were high concentrations of nitrate (53.0 mg/l), silicate (323.0 mg/l), oil products (0.22 mg/l), phenols (1.10-1.30 mg/l), and рН 8.18 near the bottom. The pollutants can come into the inlets both from coastal sources and from the open part of the Nakhodka Bay where intensive shipping occurs. Anthropogenic impact on the inlets increases recently because of new industrial construction on their coasts. Generally, according to the values of BOD and concentrations of chlorophyll a and nutrients, the area of the Kozmin and Ozero Vtoroe Bays is ranked as a mesotrophic coastal area, and according to the content of organic pollutants (oil products, phenols, detergents) - as a moderately polluted area (3rd Class of the standard scale of marine areas pollution).