Brown carbon (BrC) from ammonium and glyoxal/methylglyoxal (NH₄⁺-G/MG) reactions significantly impacts aerosol composition and radiative forcing, yet its photochemistry remains unclear. This study identifies 2-IC and M-IE as key BrC species and photosensitizers, elucidating their photodegradation pathways. Reactive oxygen species from photolysis contribute more to composition diversity than photosensitization, yielding organic acids and ring-opening products. Unlike photostable G, MG undergoes photodegradation in NH₄⁺-MG systems, driving H abstraction and forming light-absorbing aromatic carbonyls. Our experimental and thermodynamic analyses reveal M-IE’s role as a photosensitizer and highlight MG’s unexpected function as an oxidant source in atmospheric BrC chemistry.

Chamber experiments were conducted in AIDA chamber under different humidities and with presence of reactive nitrogen in aerosol or gas phase. The yield of α-pinene ozonolysis products is strongly enhanced at higher humidity, while the presence of reactive nitrogen will lead to a change in the oxidation products observed in the particle phase. Ofline FIGAERO-CIMS measurements shows that for higher humidity, organic matter with a higher oxygenated state and higher solubility are more likely to be formed in both gas and particle phase. Nitrogen-containing organics are also found in such conditions, indicating new aqueous phase SOA formation pathways.

The oxidation reactions of sesquiterpenes are an important yet underestimated source of biogenic secondary organic aerosol (bSOA). In this study, our goal is to improve the parameterization used in chemical transport models (CTM) to simulate SOA formation from sesquiterpenes. Experiments were conducted in the FORTH Atmospheric Simulation Chamber, focusing on multigeneration reactions of β-caryophyllene. The experimental data were utilized in a box-model to estimate the parameters that adequately describe SOA evolution during the two-step oxidation of β-caryophyllene. The estimated parameters were implemented in a CTM to simulate and quantify the contributions of sesquiterpene SOA to organic aerosol during the summer.

Soil and litter are significant sources of BVOCs, which can contribute to SOA formation. However, the role of leaf litter decomposition in atmospheric particle formation, particularly in the Mediterranean region, remains unclear. This study aims to better understand the potential of BVOCs emitted from litter to form SOA. To achieve this, an innovative experimental setup was developed, combining a VOC emission chamber, a flow reactor, and advanced analytical instruments (CHARON-PTR-ToF-MS, SMPS). Initial experiments with two leaf litters confirmed the system's ability to generate high VOC concentrations and, upon light exposure, the oxidation by OH radicals led to new particle formation.