1. Зарипова К. М. (Zaripova K. M.)
2. Gurov K. I.
   
   Marine Hydrophysical Institute of RAS, Sevastopol, Russian Federation (ru)
3. Тихонова Е. А. (Tikhonova E. A.)
4. Соловьева О. В. (Soloveva O. V.)

Purpose. The purpose of the study is to assess the content and spatial distribution of organic matter and petroleum hydrocarbons in the surface layer of bottom sediments in the coastal waters of the southern Kamchatka Peninsula depending on the sediment grain-size composition and the degree of coastal urbanization.

Methods and Results. The surface (0–3 cm) sediment samples were collected by a box corer aboard the R/V Professor Multanovskiy in August–September 2023. The following parameters were determined: grain-size composition – by a combined sieve method, loss on ignition – according to GOST 23740-2016, organic carbon (С_org) content – by coulometric analysis, and concentrations of chloroform-extractable substances and petroleum hydrocarbons – by gravimetric and IR spectrometry. The sediments consisted predominantly of silt-sand mixtures, with a higher silt content in the isolated bays. The content of С_org ranged from 0.02 to 3.56%, and loss on ignition ranged from 0.86 to 9.87%, with a strong correlation between the indices (r = 0.91). The concentrations of petroleum hydrocarbons and chloroform-extractable substances ranged from 0.3 to 93 and 2 to 185 mg/100 g, respectively, with their maxima being observed in Avacha Bay. The minimum concentrations (0.3–3.2 mg/100 g for petroleum hydrocarbons and 2–8 mg/100 g for chloroform-extractable substances) were noted in sandy sediments in the Khalaktyrsky Beach area, as well as in silt sediments of Vilyuchinskaya Bay. The values of both of petroleum hydrocarbons and chloroform-extractable substances positively correlated with С_org and loss on ignition. The linear regression model demonstrated that loss on ignition and the urbanization indicator jointly explained about 80% of the variation in ln(PHC).

Conclusions. The obtained results show that the organic matter content and the grain-size composition of sediments are the key factors controlling the accumulation of petroleum hydrocarbons, while coastal urbanization enhances the hydrocarbon load. Signs of chronic pollution are characteristic of Avacha Bay and several shallow bays.