Sea salt aerosols, a major aerosol type in the atmosphere, can take up water at Relative Humidities (RHs) well below deliquescence. This surface water can create chemically active environments that may catalyze reactions. However our understanding of these phenomena is still limited. In this study, we investigated phenomena on sea salt surfaces exposed to different RHs, at the nanometer scale, using Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS). At the lowest RH (7%), we observed spontaneous surface chemistry leading to the formation of oxidized chlorine species, likely chlorate (ClO3-). This study reveals a new pathway for chlorate formation in the atmosphere.

Oligomerization of organic compounds produces non-volatile dimers, but their formation mechanism remains unclear. Dimerization affects monomer vapor pressure and enhances FNP stability by suppressing evaporation. Once formed, dimers are unlikely to re-evaporate from FNPs.

Quantifying inhalable particles generated by explosions is a key factor in defining the target to be protected from such an event in the context of radioactive material. This study focuses on the particles generated by explosions in contact of concrete radioactive waste packages. The main objective is to quantify the mass of particles smaller than 10 μm in terms of aerodynamic diameter. For that purpose, we developed a protocol and measured a reasonable envelope of the mass of particles collected after concrete specimen explosions, at middle-scale.

This study focuses on detecting Saharan dust events (SDE) using in-situ aerosol optical properties and radiative forcing efficiency (RFE) at the high-altitude Helmos Hellenic Atmospheric Aerosol and Climate Change (HAC²) station in Greece. Intensive optical properties, including single scattering albedo (SSA), scattering Ångström exponent (SAE), absorption Ångström exponent (AAE), and single scattering albedo Ångström exponent (SSAAE), were assessed alongside the aerosol coarse-to-total volume concentration ratio (CV/TV). Metrics were validated using dust forecasts and air mass trajectories. During SDE, SAE and SSAAE decreased significantly, while CV/TV increased (>0.7), highlighting strong aerosol impacts on regional climate through more negative RFE.

The southeastern U.S. is home to high warm-season concentrations of sulfates and biogenic secondary organic aerosol (SOA). Changing aerosol loading and chemical speciation in the region has implications for regional air quality, radiative transfer, aqueous phase SOA production, and aerosol-cloud interactions. This presentation focuses on the relationships between aerosol optical properties, cloud condensation nuclei, aerosol size distributions and chemical speciation, measured at the NOAA and NASA federated aerosol network sites at Appalachian State University. These relationships can help elucidate how the changing aerosol composition is likely to impact regional CCN concentrations and CCN spectra, biogenic SOA production, and radiative transfer.

The BIO-MASTER project investigates the relationships between bioaerosol composition and the optical/physical properties of atmospheric aerosols in a Central Mediterranean area. Two intensive monitoring campaigns were conducted at the University of Salento, Lecce, between December 2023 and October 2024, using innovative sampling and analysis techniques. These included the WIBS-NEO sensor for fluorescence-based bioaerosol detection and the ACD-200 Bobcat sampler for particulate matter. The study employed metagenomic analysis to identify bacterial and fungal communities in the aerosol samples, revealing seasonal variation in bioaerosol composition and emphasizing the need for standardized sampling protocols.