Environment: ENEA evaluates air pollution in parks through atmospheric visibility

The atmospheric visibility index in Italian national parks as a parameter for assessing the impact of air pollution: this is the basis of the "Visibility" project, coordinated by Arma dei Carabinieri - Forestry, Environmental and Agri-food Units Command (CUFAA), with ENEA carrying out analyses on the collected samples.

A monitoring station measures the main pollutants (PM2.5, PM10, sulphates, nitrates, nitrogen dioxide, etc.) through 24-hour sampling (one every three days). The first station has been placed near Lago dei Monaci, in the Circeo National Park (Latina), and is equipped with particulate samplers and gas analyzers, a panoramic camera, and a meteorological station. The I.M.PRO.V.E. (Interagency Monitoring of Protected Visual Environment) methodology, adopted by the U.S. Environment Protection Agency (EPA) for visibility estimation, was applied here for the first time in Europe: the algorithm developed by Colorado State University quantifies a coefficient, the so-called light attenuation index, which assesses the impact of air pollutants on visual clearness. Reduced visibility is, in fact, a recognizable effect of air pollution. 

"With the 'Visibility' project, we intend to contribute to protecting the landscape, a resource for future generations as well," remarks Ettore Petralia, researcher at the Laboratory Models and Measurements for Air Quality and Climate Observations of the Sustainability Department and scientific supervisor for ENEA in the Visibility project. "To calculate the atmospheric visibility index, we are performing chemical and physical analyses in the laboratory on samples collected between March 2021 and August 2025."

Preliminary results show that an increase in the values of the light attenuation index corresponds to a decrease in long-distance optical visibility. Petralia explains: "In terms of pollutant sources, the factors that have a negative impact are both of anthropogenic origin, such as vehicular and port traffic and combustion from domestic, agricultural, and industrial activities, and of natural origin, such as the wind transport of soil material. Still, the main compounds responsible for this reduction are those related to secondary pollutants (such as ammonium nitrate and ammonium sulphate), namely they are not emitted directly into the atmosphere but derive from subsequent reactions."

From Circeo Park, monitoring was extended to mountainous areas: sampling was also conducted in the Vincheto di Celarda Nature Reserve (Feltre, Belluno), managed by CUFAA within the Dolomiti Bellunesi National Park. "The environmental situation," the researcher comments, "is different from that of Circeo Park, as it is a humid pre-alpine site. This allowed us to further verify the applicability of the methodology and the visibility index."

“Visibility” is part of the wider framework of the EU LIFE MODERn(NEC) project, which again sees CUFAA as coordinator and ENEA as a partner. The project aims to fulfil the obligations of reducing emissions and monitoring the impacts of pollution on forest and freshwater ecosystems, as set out in the European Directive 2016/2284 NEC (National Emission Ceilings).