Molecular Distributions and Compound-Specific Stable Carbon Isotopic Compositions of Plant Waxn-Alkanes in Marine Aerosols along a North-South Transect in the Arctic-Northwest Pacific Region

Abstract

A geographical source ofn-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 ofn-alkanes (homologous series of C(16)to C-34) and compound-specific stable carbon isotopes (delta C-13) ofn-C-27,n-C-29, andn-C-31. 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 CPI17-23(0.6-1.4). The occurrence of high molecular weight (HMW)n-alkanes with high CPI27-31(˃3) indicated the biogenic input of terrestrial higher plant leaf waxes in all studied samples. The delta C-13 of HMWn-alkanes was influenced by both the relative contributions from the C-3/C(4)plant sources and from fossil fuel combustions. The back-trajectory analyses provided evidence that changes in molecular distributions and delta C-13 ofn-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.