Hydrocarbons and suspended matter in the atmosphere-water boundary layer in the Barents and Kara Seas

Abstract

The concentrations and composition of hydrocarbons - HCs (aliphatic - AHCs and polycyclic aromatic hydrocarbons - PAHs) in the Barents and Kara Seas (cruises 80, 83 and 89 of the R/V «Akademik Mstislav Keldysh», August 2020, June 2021, September 2022 respectively) are analyzed in the paper. The concentrations of the HC dissolved and suspended forms were measured in the surface microlayer (SML, 100–1000 μm thick), melting ice and surface waters. Higher concentration of HCs in SML was found in suspended particulate matter (SPM). AHC concentration in SPM in the Barents Sea were lower (31–96, on average 68 μg/L) than in the Kara Sea in June 2021 (187–1051, 573 μg/L on average), where the studies were carried out in the early summer season. The concentrations of AHCs in the SPM in the SML of the Kara Sea were 3.6 times higher than in the dissolved form (127–217, on average 187 μg/L), and they were almost 15 times higher than those in the surface waters. The accumulation of organic compounds also occurs in ice, but to a lesser extent than in the SML. The composition of alkanes in SML and melting ice mainly indicates the slight influence of autochthonous processes shaping HCs. The average content of PAHs in SPM was also 4.8 times higher than that in the dissolved form. According to the markers, the influence of combustion products of marine fuel was traced in the composition of PAHs. In September 2022, AHC and PAH concentrations in the Kara Sea were lower than in June 2021: on average, 159 μg/L and 492 ng/L accordingly, that is due to a decrease in the content of SPM from an average of 1.89 to 1.21 mg/L.