| 22 Apr 2026
Continuous new particle formation in a Mediterranean coastal environment: Insights from atmospheric ions behaviour analysis
Abstract. Atmospheric new particle formation (NPF) is crucial for aerosol number concentration and for studying the production processes of secondary aerosol particles. NPF events are commonly classified based on visible particle growth, and their occurrence frequency is often underestimated. Recent methodologies propose that "quiet" NPF (QNPF) events, which are not traditionally classified as NPF events, can contribute significantly to particle number concentrations. This study presents three-years (June 2020–May 2023) of observations of ion and particle size distributions performed at the Finokalia environmental research station in Crete, Greece, using a Neutral cluster and Air Ion Spectrometer (NAIS) and a Mobility Particle Size Spectrometer (MPSS). By analysing the observed ion number size distributions and applying a nanoparticle ranking analysis method, this study reveals that QNPF events are frequent and contribute significantly to particle formation and growth in the Eastern Mediterranean. Negatively charged intermediate size ions are found to be reliable indicators of particle formation, including both classical NPF and QNPF episodes. Our analysis indicates continuous particle formation even on days traditionally classified as "non-event" days, providing fundamentally new understanding of NPF processes in the region.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Aerosol Research.
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This manuscript presents three years of observations of ion and particle size distributions at the Finokalia station in Crete, Greece, using a Neutral Cluster and Air Ion Spectrometer (NAIS) and a Mobility Particle Size Spectrometer (MPSS) to determine the NPF events in the Eastern Mediterranean. The authors applied the newly proposed method to gain fresh insights into NPF events in the marine background of the Eastern Mediterranean and examined the role of ions in identifying and classifying NPF events. The topic is timely and relevant, as NPF determining methodology and NPF occurrence in megacities located at the crossroads of Europe, Asia, and the Mediterranean remain poorly documented, and scientists try to understand the NPF mechanism. Overall, the study is well designed, clearly written, and methodologically sound. The manuscript is well within the scope of Aerosol Research Discussion after the following minor revision.
The abstract should be revised to include the article’s original findings.
The introductory text should include more up-to-date sources, and the regional NPF mechanism should be discussed in greater detail in the paragraph on line 45.
"..of the.." in Table 1 caption should be removed.
In line 145: Why did the authors select different time intervals for active and background in the four seasons? Is it possible to formulate the ranking analysis method to understand clearly?
What is the methodology of defining the cotegory of "undefined NPF"? 21% percent is need to discuss, because higher level comparing the literature.
Between lines 155-165: The results of recent studies carried out in the region should be included in the discussion in this section. The region’s unique status in terms of NPF formation should be discussed.
The seasonalty is very important on forming NPF events. So the seasonal level of NPF frequency should be added in Table 2.
It is not necessary to write "..by Dal Maso et al. (2005)" in the figure 1 caption.
Line 183: "A secondary maximum is found in October (48%), probably due to the onset of the wet period and the decrease in CS". Is there any evidence to support this finding? Such as rainfall data and also evidence that wet period increases NPF.
Section 3.1 needs further discussion with regional NPF events through the seasonality etc.
The conclusion may include the limitations and further study suggestions.