Summertime carbonaceous aerosols collected in the marine boundary layer of the Arctic Ocean

The chemistry, morphology, and microscale to nanoscale structures of carbonaceous aerosols from the marine boundary layer of the Arctic Ocean were investigated by a variety of electron microscopy techniques, including scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HRTEM), and energy‐dispersive X‐ray spectroscopy (EDS). The relative levels of particles of black carbon (BC) were determined by electron paramagnetic resonance (EPR). Polycyclic aromatic hydrocarbons (PAHs) absorbed onto BC particles were extracted by the soxhlet extraction method and analyzed by gas chromatography mass spectrometry (GC‐MS). The results show that the dominant particles of BC are char particles with spherical shape, porous structure, and high sulfur content, which are typically derived from residual oil combustion on ships. The spatial distribution of BC from ship emissions was found to be concentrated around the periphery of the Arctic Ocean, suggesting relatively intensive contamination by ships in the Russian and Canadian Arctic. The abundance of PAHs on BC particles ranges from 142 to 2672 pg/m 3 (mean = 702 pg/m 3 ), which is significantly higher than values previously measured by land‐based observation. Thus we find that ship emissions are a potentially important contributor to the PAH levels at some locations in the Arctic Ocean during the summer.