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 USD 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.

The first online instrument for the speciation of water‑soluble iron in ambient aerosols is presented. The system combines flow injection analysis with spectrophotometric detection using a liquid waveguide capillary cell. Sensitive iron speciation will help to better describe tropospheric aqueous-phase reactions driven by soluble iron, e.g. hydroxyl radical formation through Fenton chemistry. In first measurements in Berlin, ambient water-soluble-iron concentrations reached up to 47 ng m^-3.

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.

Biomass combustion for domestic heating can contribute to air pollution in residential areas with regard to 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 to, on average, twice the background level. The good-practice statement of a maximum 1 h mean of the World Health Organization is exceeded during 33.6 % of days.

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.

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.

We developed a new automated method for calculating aerosol particle growth rates. We found that the method produces results comparable to conventional approaches, while offering improved speed and ease of use.

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 reporting higher values. The results also show that OSc in mixed-VOC systems is influenced not only by products from individual precursors but also by accretion products formed through interactions between VOC products.

We trained machine learning models to estimate the number of aerosol particles large enough to form clouds and generated daily estimates for the entire globe. The models performed well in many continental regions but struggled in remote and marine areas. Still, this approach offers a way to quantify these particles in areas that lack direct measurements, helping us understand their influence on clouds and climate on a global scale.

Organic aerosols consist of complex chemical mixtures that are challenging to characterize using chemical ionization mass spectrometry alone. This study presents a method for coupling liquid chromatography and chemical ionization mass spectrometry for the offline analysis of organic aerosols. The evaluation of the method using standards and laboratory-generated and field-collected organic aerosols showed that it can provide detailed characterization of environmentally relevant mixtures.

Vehicle emissions significantly impact air quality, but distinguishing between gasoline and diesel aerosol sources in the air is still difficult. This study used advanced chemical analysis and statistical methods to discover unique aerosol molecular markers from each vehicle type. By simulating real-world driving and atmospheric ageing, researchers found specific markers for both primary and secondary particle emissions, offering a promising new approach to improve air pollution source tracking.

This study presents atmospheric ice-nucleating particle (INP) data from the Gruvebadet observatory in Ny-Ålesund. A moderate summertime increase in INP levels is observed at -15 °C but not at other temperatures (-18 and -22 °C). Conversely, a marked seasonal evolution was observed for the contribution of super-micrometer INPs, which is at its maximum throughout summer up to early autumn. We show that marine biogenic INPs may be relevant in the Arctic during seasons of reduced sea ice coverage.

This study presents a new method to measure ultrafine airborne particle concentrations down to 3 nm at high concentrations. By growing the particles into droplets, subsequently electrically charging them, and detecting the electrical signal, the system enables accurate and compact measurements of the particle number concentration. This approach is useful for onboard monitoring of vehicle emissions where space is limited and high concentrations are measured.