This study reports from an inter-laboratory comparison to assess particle size distributions of three test aerosols using 35 OPCs from 16 partners over 40 weeks. Despite a common protocol and a shared reference OPC, notable inter-instrument differences appeared, highlighting the challenge of achieving consistent results across laboratories. The resulting database cannot yet allow define good laboratory practices, but it offers a methodology and reference data to improve OPC reliability.

Black carbon particles absorb sunlight and warm the climate, but their properties change in the atmosphere. We measured how changes in soot particle shape affect size-resolved light absorption. Our results show that compacted particles absorb more light, although this effect can reverse due to competing physical processes.

The paper presents a model for the atomisation and evaporation of a stream of solvents containing less volatile analytes through a system, designed to detect the final dried particles using elastic scatter, called elastic light scatter detector. The results of simulations of the total particle concentrations as well as the final light scattered signals are compared to experiments for validation. This is the first set of simulations of this detection device.

The manuscript presents the very first measurements of droplet and particle sizes and concentrations through the parts of an Elastic Light Scatter Detector. Measurements were made using two instruments, phase Doppler particle anemometry and an aerodynamic aerosol classifier to resolve the size distribution of volatile particles upstream and dried particles downstream. The final measurements are used in a companion paper comparison with simulations.

We developed a new online method to measure water-soluble iron in airborne particles using spectrophotometry of the magenta iron-ferrozine complex. Two sampling systems were tested and worked reliably, though one underestimated iron due to shorter extraction time. The method is well suited for field applications and could support future improvements of atmospheric iron modeling.

Coastal aerosols in Scandinavian urban areas remain understudied. We examined aerosol optical properties and size distributions along Denmark's coastline. Combining in-situ data with dispersion modelling, we identified two main aerosol types: carbonaceous aerosols from fossil fuel and biomass burning and large, highly-scattering aerosols (potentially sea salt). Black carbon from in-situ data and dispersion modelling correlated well while FLEXPART underestimated the concentration.

1. Seven years hourly PNSD (10–500 nm) were measured at an urban background of Germany. 2. -2 % p. a. downward trend of T-PNC was observed. 3. Wind from Airport showed highest Nucleation Mode particles concentrations. 4. Lockdown lowered concentration of UFP on direction of airport. 5. Strong seasonal variations and weekend effects for Nucleation Mode particles were found. 6. On 30 % of all days the WHO UFP value for high concentrations was exceeded.

Biomass combustion for domestic heating can contribute to air pollution in residential areas regarding ultrafine particle concentrations. Measurements of ultrafine particle concentrations were performed in a residential area with a diffusion charge based device during winter. In the morning and evening hours the concentration increases on average to twice the background level. The good-practice statement of a maximum 1-hour mean of the World Health organization is exceeded during 33.6 % of days.

We investigated how water vapor affects the earliest steps of atmospheric aerosol formation, a key process influencing clouds and climate. By benchmarking quantum-chemical methods, we identified reliable approaches for modeling hydrated molecular clusters of common atmospheric acids and bases. We show that humidity moderately stabilizes certain clusters but only modestly alters particle formation rates. These findings sharpen our understanding of clusters and their role in aerosol formation.

Small airborne particles, influence how clouds form and how they affect climate. Our study compared eight different instruments that measure size distributions of these particles to understand the instruments' strengths and weaknesses. We found that some systems are more accurate, while others are more sensitive at tiny sizes. These results will help improve future monitoring of air quality and climate processes.

The SiMPLE-PAS is a single-pass, multi-wavelength, portable, and low-expense photoacoustic spectrometer designed to measure absorption of light by atmospheric aerosols.  It is differentiated from other PAS instruments by being much less expensive (approximately $500 total) and 3D-printed while still allowing measurements at multiple wavelengths.  The instrument has competitive detection limits and provides a blueprint for an ultra low-cost PAS to make the technique more accessible.

Charged molecular clusters, called small ions, are always present in the atmosphere. Few studies have focused on their size distribution, and motivated by this we study the size of small ions and how it varies in Hyytiälä, Finland and Beijing, China. We find that the relationship between small ion size and low-volatility vapor concentrations is strong in Hyytiälä. In both locations, we find that the small ion size has a positive relationship with cluster formation and growth.

This study examines NH₃ emissions from UK agriculture and their role in PM_2.5 formation, focusing on dairy, pig, and poultry sectors. Using regional (CMAQ) and local (ADMS) models, it finds that a 13 % NH₃ reduction only cuts PM_2.5 by ~1 % due to NH₃-rich air. CMAQ may underestimate PM_2.5, while ADMS shows emissions disperse within 700 m. The study highlights the value of combining models to better understand pollutant spread and improve PM_2.5 control strategies.

This study analysed the average carbon oxidation state (OSc) during secondary organic aerosol formation from mixed volatile organic compounds (VOCs) using three mass spectrometry techniques. Notable discrepancies in OSc were observed across the techniques, with FIGAERO-CIMS keep reporting higher values. The results also shown that OSc in mixed VOC systems is influenced not only by products from individual precursors but also by unique compounds formed through interactions between VOC products.

We developed a new automated method for calculating aerosol particle growth rates. Based on 14 years of measurements from Hyytiälä, Finland, the method produces results comparable to conventional approaches, while offering improved speed and ease of use.

This study examined particle emissions from a large-scale biomass heating plant. Efficient flue gas cleaning, especially with bag-house filters, significantly reduced primary emissions. However, the potential for secondary aerosol formation was found to be 100–1000 times higher than primary emissions, highlighting the need for further research to support air quality and climate goals.

The measurement of particle mass concentrations in gases is essential for monitoring emissions from engine exhaust or atmospheric pollutants. Various instruments allow for real-time concentration monitoring, but few studies have evaluated the accuracy and reliability of these measurements. We present the results of an intercomparison between several mass concentration measurement instruments to assess their ranges of validity, providing valuable guidance for future users of these devices.

New particles form in the atmosphere and can influence the climate. We studied Arctic new particle formation (NPF) from 2022 to 2024 at the Zeppelin Observatory, on Svalbard. NPF occurs from April to November, peaking in late spring as sunlight increases. Some particles measured on-site grow large enough to seed clouds. Sunlight and existing aerosol particles strongly impact the likelihood of NPF, which mainly originates from marine regions, particularly the Greenland Sea.

Ensuring that all measuring instruments deliver reliable results is an important task. For aerosol measurement, a health-related parameter is not yet well defined worldwide. We have therefore developed a test bench to evaluate and compare instruments on this key parameter. Based on the success of an initial comparison with our instruments, we underline the feasibility of a standardized test and offer a framework for improving accuracy and consistency of aerosol size distribution assessments.

We investigated the space charge influence on the aerosol neutralization principle used in all aerosol measurement instruments. We found that the space charge cause ions to separate unevenly, leading to different rates of neutralization in different parts of the inlet, impacting the effectiveness of the neutralization process.

Although spray flame synthesis (SFS) is a promising approach to prepare nano materials with tailored properties, the impurity formation is not fully understood in SFS. To contribute to this topic, maghemite nanoparticles were prepared by SFS, and two complementary experimental approaches were used to investigate the evolution of soot and carbonaceous surface adsorbates. The methodological procedure and the data provided can be used to denote/compare SFS-materials more reliably in the future.

Several papers have reported on electrospray technique and they have shown that uniform thin films with different surface morphologies can be deposited. Nonetheless, the studies do not give a systematic way of designing different surface morphologies and most outcomes are based on a trial-and-error method. Therefore, in this study a systematic way of designing thin films of different surface morphologies using electrospray technique has been developed.