Sources of Southern Hemisphere Marine Aerosols: Insights from Carbonaceous Fraction Concentration and Stable Carbon Isotope Analysis
Description
The data for our study were derived from a robust collection of aerosol samples gathered over a span of seven years, from 2013 to 2020, during six separate Antarctic expeditions that traversed latitudes from 28°N to 78°S. This extensive dataset allowed us to conduct a thorough investigation into the nature of marine carbonaceous aerosols, particularly in the under-studied Southern Hemisphere. Our analysis focused on the concentrations of organic carbon (OC) and elemental carbon (EC) present in the aerosol samples. On average, we found the OC concentration to be 1.29 ± 1.15 μg/m^3, while the EC concentration averaged at 0.13 ± 0.18 μg/m^3. These values, however, were not uniform across all samples; we observed a spectrum of concentrations that reflected the varying influence of background marine conditions and significant continental transport. The ratio of OC to EC in our samples indicated that fossil fuel combustion was the predominant continental influence on marine aerosols. Further insights were gained from the stable carbon isotope ratio (δ^13C_TC), which ranged from -22.3‰ to -28.4‰, with an average value of -26.3‰ across all samples. Employing a three-endmember isotopic source model, we were able to determine the contributions of continental carbonaceous aerosols. Our findings revealed a dominant continental contribution in the aerosols over the Eastern Indian Ocean, accounting for 81±4% of the carbonaceous material. In contrast, samples from the Southern Ocean showed a lower continental influence, with a contribution of 44±20%. Interestingly, the primary marine aerosols from the Southern Ocean were found to have a significantly higher proportion of fresh carbon, contributing 52±19% to the aerosol composition. This suggests a notable marine biological influence on the aerosols in this region. Additionally, our research points to the potential role of Southern Ocean sea ice in modulating emissions from the fresh carbon pool. Overall, the data collected and analyzed in this study provide valuable insights into the distribution and composition of marine carbonaceous aerosols, elucidating their potential impacts on climate change and the intricate dynamics of the ocean-atmosphere carbon cycle.