Summertime Aerosol Composition in Southern Greenlandic Fjords: Impacts of Sources and New Particle Formation Events.

Arctic fjord systems are a dynamic interface between ocean, ice, and land, with high summertime biological activity. We present the first aerosol chemical composition measurements from two summer campaigns on the research vessels Forel and Sanna in the fjords near Narsaq, South Greenland, using nanoelectromechanical systems Fourier transform infrared spectroscopy (NEMS-FTIR). Organic matter concentrations (median 1.1 μg m-3) exceeded those at High Arctic and midlatitude coastal sites, reflecting the ability of fjords to act as strong aerosol sources. Cluster analysis of FTIR spectra resolved three recurrent aerosol types, with interannual differences linked to phytoplankton bloom timing. To further resolve simultaneous source contributions, positive matrix factorization was applied, identifying a primary marine (53%) and secondary marine (47%) factor, the latter recognized as methanesulfonic acid-containing via characteristic fingerprint-region absorptions. Amine concentrations exceeded those of open-ocean primary marine aerosol, attributed to secondary condensation of gas-phase amines from local sources onto acidic sea spray. High-time-resolution sampling captured chemical composition changes during new particle formation events, with particle number size distributions confirming that such events systematically shift aerosol composition toward a secondary character. These results establish that aerosol in southern Greenlandic fjords is predominantly marine-biogenic and will respond to ongoing glacier retreat and associated changes in fjord productivity.