New Particle Formation and Condensable Vapours in an Arctic Site: Ny-Ålesund

INTRODUCTION 

New particle formation (NPF) is an important source of aerosol particles in the Arctic, the dynamics and drivers of which are still not fully understood. The concentrations of precursor gases, such as sulfuric acid (SA), methane sulfonic acid (MSA), iodic acid (IA), and highly oxygenated organic molecules (HOMs), are strongly linked with the occurrence and strength of NPF. Currently, though, measurement data of NPF, as well as precursor gases, in the Arctic remains extremely limited.

Here we present some preliminary results of our in-situ measurements deployed to study NPF in the Svalbard archipelago. The region is mapped by snow-, ice-, and permafrost-covered land, limited vegetation, and a strong marine influence of the sea ice. SA, MSA, and IA concentrations at the site are interlinked with the behaviour of ocean and sea ice. The terrestrial vegetation emits volatile organic compounds (VOC), which in the atmosphere convert to HOMs. As the Arctic is rapidly transforming due to climate change, all these ecosystems are being altered, which also affects the dynamics of NPF.

METHODS

The measurements considered in this work have been conducted at the Ny-Ålesund Research Station (Svalbard) and, originally started in 2017, represent the longest time series of aerosol data measured with mass spectrometry in the Arctic. In this work, the Arctic summer of 2024 is studied. 

A nitrate-based chemical ionisation atmospheric pressure interface time-of-flight mass spectrometer (CI-APi-TOF, Tofwerk AG.) is used to measure precursor vapour concentrations and identify ion clusters in the ambient air. A neutral cluster and air ion spectrometer (NAIS, Airel Ltd) and a cluster ion counter (CIC, Airel Ltd) are used to monitor neutral particle (2-42nm) and ion cluster (0.8-42nm) size distribution. The measurements are paired with solar radiation data gathered at the Climate Change Tower by CNR (Mazzola et al., Rend. Fis. Acc. Lincei 27, 2016).

RESULTS AND DISCUSSION

A SA/MSA ratio larger than 1 was observed almost throughout the measurement period (Figure 1). This is contrary to previous results from the site by Beck et al. (Geophysical Research Letters 48, 2021). The difference could be due to yearly variation in the oceanic phytoplankton spring bloom, which affects atmospheric MSA concentrations Arctic.

From the preliminary analysis for one week, a diurnal cycle for SA and MSA was observed (Figure 2). NPF occurrence appeared to correlate with radiation intensity, as well as SA and MSA concentrations.

CONCLUSIONS 

These preliminary results highlight the importance of long-term data sets in monitoring Arctic NPF, as they imply strong inter-annual variation in precursor gas concentrations, which may initiate NPF and growth of particles at the study site.

 

Figure 1. Daily mean values for precursor gas concentrations measured with CI-APi-TOF (May-August 2024).  

 

Figure 2. Upper panel: 1.5-hour average values of net short-wave radiation and precursor gas concentrations from a seven-day period with NPF. Lower panel: particle size distribution measured with NAIS, from the same period.