We present a characterization of reactive gases (RG: O3, NO, NO2,SO2, CO) and methane (CH4) variability in the central Mediterranean basin,analyzing in situ measurements at three new permanent WMO/GAW Observatories in Southern Italy: Capo Granitola – CGR (Sicily), Lamezia Terme – LMT (Calabria) and Lecce – ECO (Apulia). At all the measurement sites, a combination of the breeze wind system (especially at CGR and LMT),PBL dynamics, anthropogenic/natural emissions, and photochemistry lead the appearance of well-defined diurnal cycles for the observed RG. According to O3/NOx variability, local emissions appeared to influence CGR and LMT (no NOx data were available for ECO during the period of study) in 4% and 20% of the hourly data, nearby sources in 39% and 40%, remote sources in 31% and 14%, while background O3/NOx were observed in 26% of cases for both the stations. Most of the background O3/NOx were observed during daytime, when offshore air masses usually affected the measurement sites. Local sources of CH4 at CGR can be related to biogenic (oxic) emissions from biomasses along the coastline, while emissions from live stocks can represent a local source of CH4 at LMT. Finally, we provide first hints about the export of O3 from Sicily/Southern Italy to the Mediterranean Sea by comparing simultaneous observations at CGR and Lampedusa (LMP), a small island in the middle of the Strait of Sicily where a WMO/GAW Regional Station is located. In summer,O3 increased by some 7 ppb for transport times lower than 48 h, while no statistical significant differences were observed for travel time longer than 48. This would suggest that photochemical O3 production occurred within air-mass travelling from CGR to LMP, but also that the central Mediterranean MBL represents a O3 sink for relatively aged air-masses.

The RHAPS (Redox-Activity And Health-Effects Of Atmospheric Primary And Secondary Aerosol) project was launched in 2019 with the major objective of identifying specific properties of the fine atmospheric aerosol from combustion sources that are responsible for toxicological effects and can be used as new metrics for health-related outdoor pollution studies. In this paper, we present the overall methodology of RHAPS and introduce the phenomenology and the first data observed. A comprehensive physico-chemical aerosol characterization has been achieved by means of high-time resolution measurements (e.g., number size distributions, refractory chemical components, elemental composition) and low-time resolution analyses (e.g., oxidative potential, toxicological assays, chemical composition). Preliminary results indicate that, at the real atmospheric conditions observed (i.e., daily PM₁ from less than 4 to more than 50 μg m⁻³), high/low mass concentrations of PM₁, as well as black carbon (BC) and water soluble Oxidative Potential (WSOP,) do not necessarily translate into high/low toxicity. Notably, these findings were observed during a variety of atmospheric conditions and aerosol properties and with different toxicological assessments. Findings suggest a higher complexity in the relations observed between atmospheric aerosol and toxicological endpoints that go beyond the currently used PM₁ metrics. Finally, we provide an outlook to companion papers where data will be analyzed in more detail, with the focus on source apportionment of PM₁ and the role of source emissions on aerosol toxicity, the OP as a predictive variable for PM₁ toxicity, and the related role of SOA possessing redox-active capacity, exposure-response relationships for PM₁, and air quality models to forecast PM₁ toxicity.

Unlike stratospheric ozone (O₃), which is beneficial for Earth due to its capacity to screen the surface from solar ultraviolet radiation, tropospheric ozone poses a number of health and environmental issues. It has multiple effects that drive anthropogenic climate change, ranging from pure radiative forcing to a reduction of carbon sequestration potential in plants. In the central Mediterranean, which itself represents a hotspot for climate studies, multi-year data on surface ozone were analyzed at the Lamezia Terme (LMT) WMO/GAW coastal observation site, located in Calabria, Southern Italy. The site is characterized by a local wind circulation pattern that results in a clear differentiation between Western-seaside winds, which are normally depleted in pollutants and GHGs, and Northeastern-continental winds, which are enriched in these compounds. This study is the first detailed attempt at evaluating ozone concentrations at LMT and their correlations with meteorological parameters, providing new insights into the source of locally observed tropospheric ozone mole fractions. This research shows that surface ozone daily and seasonal patterns at LMT are “reversed” compared to the patterns observed by comparable studies applied to other parameters and compounds, thus confirming the general complexity of anthropogenic emissions into the atmosphere and their numerous effects on atmospheric chemistry. These observations could contribute to the monitoring and verification of new regulations and policies on environmental protection, cultural heritage preservation, and the mitigation of human health hazards in Calabria.

We describe and implement a data selection algorithm aimed at identifying background atmospheric CO₂ observations from in situ continuous measurements. Several selection criteria for detecting the background data have been developed and are currently used: the main objective of this work was to define a common methodology to extract the atmospheric background signal minimizing heterogeneities due to the use of different selection algorithms. The algorithm used in this study, (BaDS, Background Data Selection) was tested and optimized using data (from 2014 to 2018) from four Italian stations characterized by markedly different environmental conditions (i.e., mountain, coastal and marine): Plateau Rosa (PRS), Mt. Cimone (CMN), Capo Granitola (CGR) and Lampedusa (LMP). Their locations extend from the Alps to the central Mediterranean. The adopted algorithm proved to be effective in separating the local/regional from the background signal in the CO₂ time series. About 6% of the data at LMP, 11% at PRS, 20–38% at CMN and 65% at CGR were identified as non-background. LMP and PRS can be used as reference sites for the central Mediterranean, while CMN and CGR were more impacted by regional sources and sinks. Finally, we discuss a possible application of BaDS screened data.