Analysis of Local-to-Remote Source Variability During the First 2020 COVID-19 Lockdown in Calabria, Southern Italy: New Insights from the Implementation of the ONRPI Methodology

Air pollution is among the key topics in environmental policies and mitigation policies. Governments and institutions worldwide are working towards a better understanding of the phenomenon and means to reduce its impact on the environment and human health. In early 2020, the COVID-19 pandemic forced many countries to introduce strict regulations, effectively stopping non-essential anthropic activities. Italy had a pioneering role in this regard, anticipating other countries in Europe and across the world. These exceptional circumstances caused the concentrations of pollutants in the atmosphere to reach lower levels, thus allowing researchers to evaluate a number of hypotheses concerning the contribution of anthropogenic emissions. At the Lamezia Terme (code: LMT) World Meteorological Organization—Global Atmosphere Watch (WMO/GAW) regional station in Calabria, Italy, previous research highlighted the effects of governmental restrictions on the concentrations of gases (carbon monoxide, CO; carbon dioxide, CO2; methane, CH4, nitrogen oxides, NOx) and aerosols (black carbon, BC). In this work, sulfur dioxide (SO2) and ozone (O3) are also evaluated and all parameters are subject to the analysis based on the O3/NOx ratio, the ONRPI (Ozone to Nitrogen Oxides Ratio Proximity Indicator), which has been widely used at LMT to verify the balance between local and remote sources of emission. The implementation of this method to the first 2020 COVID-19 lockdown in the country has allowed significant improvement in our understanding of the variability of all evaluated parameters at the site, assessing with greater detail weekly cycles and day–night contrasts, and the influence of local and remote sources of emission.