Isabella Zaccardo

As part of the ACTRIS research infrastructure, a six-month study (May–October 2024) was conducted at the CNR-IMAA Atmospheric Observatory (CIAO, Southern Italy) to characterize non-refractory submicron aerosol (NR-PM₁). Measurements were conducted in real time using a time-of-flight aerosol chemical speciation monitor (ToF-ACSM) and highlighted the predominant presence of organic aerosol (OA), with values reaching 49.5 µg m⁻³. During the study period, nitrate and ammonium concentrations remained below 2 µg m⁻³ on average, while sulfate concentrations showed normal variation during the analysis period (maximum value of 11.70 µg m⁻³). The daily variability of concentrations was influenced by both boundary layer dynamics and local emission variations. The calculated charge and mass balances allowed us to study the good neutralization of PM₁ in the atmosphere. The composition of the organic aerosol was dominated by oxygenated species, with a small contribution from biomass combustion. Ultimately, these results provide an excellent starting point for understanding the aerosol chemical composition and seasonal variability at the site, ahead of future analyses and comparisons within the ACTRIS of which the observatory is part.

This study investigates the potential influence of Saharan dust intrusions on the stable carbon isotopes of methane (CH₄) and carbon dioxide (CO₂), using continuous in situ measurements from the ICOS (Integrated Carbon Observation System) atmospheric station at the CNR-IMAA Atmospheric Observatory (CIAO) in Tito, Basilicata, southern Italy. The analysis builds upon the recent investigation of a two-month isotopic dataset (20 February–20 April 2025), which identified anomalous isotopic behavior in March, coinciding with three distinct dust events. The observations reveal shifts in δ¹³C–CH₄ values that align temporally with the dust intrusions, accompanied by a decrease in CH₄ mole fractions. Such patterns could suggest fractionation processes affecting CH₄, potentially driven by enhanced oxidation promoted by mineral aerosols. At the same time, δ¹³C–CO₂ shows a gradual decline, deviating from the typical springtime enrichment associated with intensified photosynthetic uptake of ¹²CO₂. This unexpected decrease suggests that dust-related radiative effects, particularly the attenuation of incoming solar radiation, may inhibit photosynthesis, thereby altering the isotopic composition of atmospheric CO₂. Consistently, CO₂ mole fractions exhibit a modest increase during periods of declining δ¹³C–CO₂, reinforcing the interpretation of reduced photosynthetic activity. These findings provide new observational data beyond existing studies from Atlantic regions and highlight the need for further research on the role of mineral dust in shaping greenhouse gas isotopic variability in the Mediterranean, where such events are frequent and climatically relevant.

Carbon isotope fractionation is an efficient tool used for the discrimination and differentiation of sinks and emission sources. Carbon dioxide (CO₂) and methane (CH₄) are among the key drivers of climate change, and a detailed evaluation of variations in the ¹³C/¹²C ratio in either compound provides vital information for the field of atmospheric sciences. The Italian atmospheric ICOS (Integrated Carbon Observation System) consortium is currently implementing δ¹³C-CO₂ and δ¹³C-CH₄ measurements, with four observation sites now equipped with Picarro G2201-i CRDS (Cavity Ring-Down Spectrometry) analyzers. In this work, results from the first two months of measurements performed at the Potenza station in southern Italy between 20 February and 20 April 2025 are presented and constitute the first evaluation of continuous atmospheric δ¹³C-CO₂ and δ¹³C-CH₄ measurements from an Italian station. These results provide a first insight on how these measurements can improve the current understanding of CO₂ and CH₄ variability in the Italian peninsula and the central Mediterranean sector. Although preliminary in nature, the findings of these measurements indicate that fossil fuel burning is responsible for the observed peaks in CO₂ concentrations. CH₄ has a generally stable pattern; however, abrupt peaks in its isotopic delta, observed during March, may constitute the first direct evidence in Italy of Saharan dust intrusion affecting carbon isotope fractionation in the atmosphere. This study also introduces an analysis of the weekly behavior in isotopic deltas.

The Integrated Carbon Observation System (ICOS) is the reference Research Infrastructure (RI) for the observation of greenhouse gases (GHGs) across Europe, providing standardised, long-term and high-precision measurements of the most relevant species (CO₂, CH₄, CO, etc.). The ICOS Atmosphere network currently extends throughout the continent, although the density of stations in the Mediterranean area is still low compared to Central and Northern Europe. In this context, the recently implemented class 1 continental station near Potenza in Basilicata, Italy—station code: POT—represents an important step forward in the extension of the ICOS atmosphere domain across the South, reducing the large spatial gaps existing between ICOS sites within the Mediterranean basin. Herein, we provide a description of the new ICOS POT station and the site where it operates, focusing mostly on the technical setup of the sampling system which plays a key role in GHG measurements. With a strong technical connotation, the present paper aims to be beneficial for the ICOS atmosphere community and those stations that intend to join the network in the future, providing an accurate description of the station at the level of single components. Moreover, a brief overview of the peculiarities of the site and the scientific perspectives to be pursued, together with very preliminary data collected at the new ICOS station, are presented. Preliminary data collected during a short campaign are compared with STILT (Stochastic Time-Inverted Lagrangian Transport) model results as a first test of the measurements and to provide a first insight of the specific Potenza situation in terms of GHG concentrations.