We developed a new method to measure how particles absorb light as they change in size, which is critical for understanding their climate impact. Our approach uses a sensitive instrument that measures light absorption directly from particles in real time. By pairing this with a device that sorts particles by size, we achieved accurate size-resolved measurements. Our findings closely match theoretical models, offering a promising tool for future research into how particles influence climate.

This study examines new particle formation (NPF) in the Bolivian Andes at Chacaltaya mountain (CHC) and the urban El Alto–La Paz area (EAC). Days are clustered into four categories based on NPF intensity. Differences in particle size, precursor gases, and pollution levels are found. High NPF intensities increased Aitken mode particle concentrations at both sites, while volcanic influence selectively diminished NPF intensity at CHC but not EAC. This study highlights NPF dynamics in the Andes.

We assessed the performance of four cascade impactors for collecting and analyzing organic markers in airborne ultrafine particles (UFPs) under lab and field conditions. The cutoff was influenced by the impactor design and aerosol mixture. Two key factors caused variations in mass concentrations: the evaporation of semi-volatile compounds and the "bounce-off" of larger particles and fragments. Our findings reveal the challenges of analyzing organic marker mass concentrations in airborne UFPs.

Aersols are important in many parts of industry and research. To learn more about aerosols, especially when they contain nanoparticles, the Centrifugal Differential Mobility Anlayser (CDMA) presented here allows us to measure the mobility-equivalent diameter and the Stokes equivalent diameter at the same time. The result is a 2D property distribution that provides deeper information about the entire particle collective than the isolated measurement principles.

Our study explores particles in Arctic soils and streams that influence ice formation in clouds. By analyzing these environments, we identified specific microorganisms producing these particles. This research, which measured these particles in Arctic streams for the first time, provides new insights into their ecological role and transfer from soil to water. Our findings help us understand their production, sources, and potential impact on climate.

Aerosol formation is an important process for our global climate. However, there are high uncertainties associated with the formation of new aerosol particles. We present quantum chemical calculations of large atmospheric molecular clusters composed of sulfuric acid (SA), ammonia (AM), and dimethylamine (DMA). We find that mixed SA–AM–DMA systems cluster more efficiently for freshly nucleated particles compared to pure SA–AM and SA–DMA systems.

We present a new photoacoustic instrument for simultaneous measurement of aerosol light absorption at multiple wavelengths. High performance is reached by using an optically read cantilever microphone, which allows for highly sensitive absorption measurements at a compact size. Performance in field conditions is demonstrated with black carbon monitoring at an air quality measurement station, where our results agree well with reference instruments deployed at the site.

Using quantum chemical methods, we studied the uptake of first-generation oxidation products onto freshly nucleated particles (FNPs). We find that pinic acid can condense on these small FNPs at realistic atmospheric conditions, thereby contributing to early particle growth. The mechanism involves two pinic acid molecules interacting with each other, showing that direct organic–organic interactions during co-condensation onto the particle contribute to the growth.

We studied how nanoparticles form in the atmosphere at two different altitudes in Cyprus, focusing on how meteorology impacts this process. Using data from two sites, we found that air from lower regions carries particles up to higher areas, affecting air quality and potentially climate. Our findings help improve understanding of how particles form and grow in the air, which is important for predicting changes in climate and air pollution in the future.

The COVID-19 lockdown measures in 2020 reduced emissions of various substances, improving air quality. However, PM_2.5 stayed unchanged due to NH₃ and related chemical transformations. Higher humidity favoured more SO₄^2- production, as did the accumulated NH₃. Excess NH₃ reacted with HNO₃ to make NO₃^-. In high-NH₃ conditions such as those in 2020, a small reduction in NO_x levels drove faster oxidation of NO₃^- and slower deposition of total inorganic NO₃^-, causing high secondary PM_2.5.

Acyl peroxy radicals can act as atmospheric oxidants of unsaturated hydrocarbons if their 1) unimolecular reactions are slow and 2) bimolecular accretion reactions are fast. Using theoretical tools, we show which acyl peroxy radicals should be considered oxidants in the atmosphere.

The study explores the formation of small soot clusters by precursor molecules at high temperature. Higher temperature speeds up the decomposition of gas molecules, accelerating the formation of cyclic structures decorated by aliphatic chains. This research offers new insights into the early steps of soot formation, which could help develop more informed kinetic models for pyrolysis and combustion processes.