Aerosol organic matter composition during the US GEOTRACES Pacific Meridional Transect (GP-15)

Aerosols over marine environments are important for their roles impacting Earth’s radiative budget in the atmosphere and delivering organic matter (OM), macro- and micro-nutrients, and pollutants to remote parts of the ocean. Aerosol OM, in particular, is a potential carbon source for marine heterotrophs and may influence primary producers through the delivery of dissolved organic nitrogen and organic-trace metal complexes. Our understanding of aerosol OM quantities and composition, and the factors that control those quantities and compositions, is, however, lacking due in large part to the difficulty in sampling aerosols in remote marine environments. High volume aerosol particulate samples (n=22) were collected on a meridional transect spanning 75° of latitude between Alaska and Tahiti and analyzed for their organic carbon quantities and organic matter composition. The highest mean aerosol particulate organic carbon concentrations were observed between 40 and 60° N latitude (0.92 ± 0.5 μg C m^-3) with relatively consistent concentrations observed at lower latitudes (20-40° N: 0.53 ± 0.11 μg C m^-3, 0-20° N: 0.57 ± 0.12 μg C m^-3, 0-20° S: 0.53 ± 0.15 μg C m^-3). Air mass back trajectory analyses for these samples revealed the majority of the samples to be influenced by marine air masses within 5 days prior to sampling with differences in the oceanic source regions. Aerosol water soluble organic carbon quantities and compositions (via excitation emission matrix spectroscopy) will be assessed in the context of these air mass back trajectories and cruise environmental parameters (e.g., wind, temperature, humidity). The results from this project will provide important information regarding aerosol organic matter composition in remote marine environments that can be used to assess its potential impacts on oceanic primary and secondary production.