Influence of Air Mass Source Regions on Signatures of Surface-Active Organic Molecules in Size Resolved Atmospheric Aerosol Particles

The physical and chemical properties of atmospheric aerosolparticlesdepend on their sources and lifetime in the atmosphere. In coastalregions, sources may include influences from marine, continental,anthropogenic, and natural emissions. In this study, particles inten diameter-size ranges were collected, and particle number sizedistributions were measured, at Skidaway Island, GA in May and June2018. Based on air mass back trajectories and concentrations of majorions in the particles, the air mass source regions were identifiedas Marine Influenced, Mixed, and Continental Influenced. Organic moleculeswere extracted from the particles using solid-phase extraction andcharacterized using tensiometry and high-resolution mass spectrometry.The presence of surfactants was confirmed in the extracts throughthe observation of significant surface tension depressions. The organicformulas contained high hydrogen-to-carbon (H/C) and low oxygen-to-carbon(O/C) ratios, similar to surfactants and lipid-like molecules. Inthe Marine Influenced particles, the fraction of formulas identifiedas surfactant-like was negatively correlated with minimum surfacetensions; as the surfactant fraction increased, the surface tensiondecreased. Analyses of fatty acid compounds demonstrated that organiccompounds extracted from the Marine Influenced particles had the highestcarbon numbers (18), compared to those of the Mixed (15) and ContinentalInfluenced (9) particles. This suggests that the fatty acids in theContinental Influenced particles may have been more aged in the atmosphereand undergone fragmentation. This is one of the first studies to measurethe chemical and physical properties of surfactants in size-resolvedparticles from different air mass source regions.

Automated summary

In this study, particles in ten diameter-size ranges were collected and analyzed to determine the physical and chemical properties of surfactants in different air mass source regions. The results showed that the presence of surfactants in the particles was confirmed, and their concentrations were negatively correlated with surface tension. Organic compounds extracted from particles influenced by marine sources had higher carbon numbers and exhibited characteristics similar to surfactants and lipid-like molecules. This study provides valuable insights into the sources and properties of atmospheric aerosol particles.