Molecular Distributions and Compound-Specific Stable Carbon Isotopic Compositions of Plant Wax <i>n</i>-Alkanes in Marine Aerosols along a North–South Transect in the Arctic–Northwest Pacific Region

A geographical source of <i>n</i>-alkanes in marine aerosols was assessed along a North–South transect in the Arctic–Northwest Pacific region. Marine aerosol samples were collected during the ARA08 cruise with the R/V Araon between 28 August and 28 September 2017. We investigated molecular distributions of <i>n</i>-alkanes (homologous series of C₁₆ to C₃₄) and compound-specific stable carbon isotopes (δ¹³C) of <i>n</i>-C₂₇, <i>n</i>-C₂₉, and <i>n</i>-C₃₁. Unresolved complex mixtures (UCM) showed a latitudinal trend from the Arctic Ocean to the northwest Pacific Ocean, highlighting an increasing influence of the plume of polluted air exported from East Asian countries. The anthropogenic input was further evidenced by high U/R ratios (>5) and low CPI_17–23 (0.6–1.4). The occurrence of high molecular weight (HMW) <i>n</i>-alkanes with high CPI_27–31 (>3) indicated the biogenic input of terrestrial higher plant leaf waxes in all studied samples. The δ¹³C of HMW <i>n</i>-alkanes was influenced by both the relative contributions from the C₃/C₄ plant sources and from fossil fuel combustions. The back-trajectory analyses provided evidence that changes in molecular distributions and δ¹³C of <i>n</i>-alkanes were due to the long-range atmospheric transport of anthropogenic and biogenic organic materials from North American and East Asian countries to the Arctic Ocean and the remote northwest Pacific Ocean, respectively.