The role of Base molecules in AErosol formation

Project Information

BAE

Grant agreement ID: 101076311

DOI

10.3030/101076311

EC signature date 14 February 2023

Start date 1 May 2023

End date 30 April 2028

Funded under

• European Research Council (ERC)

Total cost

€ 2 248 644,00

EU contribution

€ 2 248 644,00

Coordinated by

THE CYPRUS INSTITUTE
Cyprus

Periodic Reporting for period 1 - BAE (The role of Base molecules in AErosol formation)

Reporting period: 2023-05-01 to 2025-10-31

Summary of the context and overall objectives of the project

Aerosol formation and growth mechanisms need to be better understood to improve air quality and weather prediction models, and
reduce uncertainty of radiative forcing in climate change projections. Globally, half of the aerosol population is formed via gas-to-particle
conversion and the fraction exceeds 90% in high latitudes. In many locations, the initial molecular cluster forms from sulphuric acid
and ammonia or dimethylamine. Growth to an aerosol particle is often explained by the condensation of sulphuric acid, methanesulfonic
acid and highly oxygenated organic compounds. While the roles of strong acids and organic compounds and their oxidation channels are
quantified in laboratory and field studies, cation detection and neutral atmospheric base measurements are notably under-represented.
An important innovation of this project will be the direct measurement of cations and neutral base molecules and clusters based on mass
spectrometry. Ammonia, a base predominantly emitted by agriculture, is a key air pollutant in the formation of fine particulate matter
(PM2.5). In western Europe, up to half of PM2.5 is attributed to ammonia pollution because of its ability to form aerosols in reactions with
common atmospheric acids. Current atmospheric models do not include amines, which can form aerosol particles at a 1000-times faster
rate than ammonia. To uncover the composition and level of toxicity of PM2.5 as well as the scattering and absorption of sunlight by
aerosol particles, it is critical to understand the atmospheric chemistry and molecular pathways that control their formation and growth.
The project will focus on the role of base molecules in the formation of new particles and their fate in the atmosphere and is led by
an established PI with a demonstrated history in ground breaking nanoaerosol and precursor studies. It will underpin the modelling of
atmospheric aerosol processes, which are subject to major precursor emission changes in Europe and beyond.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The ERC-funded BAE project aims to resolve one of the most critical knowledge gaps in atmospheric science: the role of atmospheric base molecules in new particle formation (NPF) and their broader impact on climate via cloud formation. Despite their importance, base compounds such as amines have remained difficult to measure directly in ambient air due to their low concentrations and chemical reactivity.

During the first phase of the project, BAE successfully established a state-of-the-art measurement platform by acquiring and integrating cutting-edge instrumentation, including a MION-Orbitrap mass spectrometer, a Neutral cluster and Air Ion Spectrometer (NAIS), and an upgraded Particle Size Magnifier (PSM 2.0). These tools enable simultaneous physical and chemical observations of freshly nucleated atmospheric particles, providing a unique capability to study the molecular pathways of aerosol formation.

Initial research focused on Cyprus, a complex and underexplored environment for NPF. A dedicated field campaign (SPICY) investigated how planetary boundary layer evolution influences NPF occurrence. The results were published in:
Deot et al. (2025): "Effect of planetary boundary layer evolution on new particle formation events over Cyprus," Atmospheric Research, https://ar.copernicus.org/articles/3/139/2025/ar-3-139-2025.html

To frame the scientific foundation of the project, a high-impact review was published on the role of amines in aerosol formation:
Kanawade & Jokinen (2025): "Atmospheric amines are a crucial yet missing link in Earth’s climate via airborne aerosol production," Communications Earth & Environment, https://doi.org/10.1038/s43247-025-02063-0

The BAE project has also enabled the formation of a dedicated research group, supported the recruitment and training of PhD students, and initiated international collaborations such as CAINA, which investigates NPF in nitrogen-polluted environments. Through this collaboration, the project has extended its scientific impact by providing state-of-the-art instrumentation for molecular-level NPF studies, helping to build a more holistic understanding of aerosol life cycles—from nucleation to cloud interaction.

Despite some delays in infrastructure readiness, the project is on track to deliver key insights into the molecular origins of climate-relevant atmospheric particles, supported by advanced instrumentation and international cooperation.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

One of the most notable and unplanned advances during the initial phase of the BAE project arose from reanalysis of earlier datasets from polar environments, target region for upcoming base molecule studies in pristine environment. While validating the nitrate-CI-APi-TOF instrumentation and establishing the research group, I revisited springtime datasets collected in polar regions. Surprisingly, these measurements revealed previously undetected oxidised mercury species present as halide clusters, suggesting a potentially novel pathway for detecting atmospheric mercury using chemical ionization mass spectrometry. This finding was not part of the original project plan and emerged serendipitously through foundational research activities during the project's ramp-up phase. A manuscript describing these findings has recently been submitted to Nature. If validated, this represents a breakthrough in atmospheric trace metal detection, potentially enabling the direct molecular identification of oxidised mercury species that has been a long-standing analytical challenge. The finding also opens the door to developing new chemical ionization schemes using halide ions, which may extend beyond mercury detection.

Based on these promising results, a proof-of-concept (POC) grant application is currently in preparation to pursue this line of research and explore technological development for halide-based ion chemistry. This unexpected result illustrates how foundational project activities can lead to significant and unanticipated scientific advances well beyond the initial scope of the project.