Understanding the impact of large fires in air quality in a Mediterranean area

Fires have been a natural component of Mediterranean ecosystems for centuries, contributing to their ecological balance. However, they also release significant amounts of smoke and various pollutants like carbon monoxide, methane, nitrous oxide, nitrogen oxides, volatile organic compounds, and particulate matter (PM). The emissions not only compromise air quality but also pose a threat to human health, particularly for those with chronic heart and lung diseases. These impacts have been largely studied in the United States and in neighboring countries, while in the Euro-Mediterranean continent the studies available on the patterns of wildfires and fire emissions are more limited. However, the increase in the frequency of large fires recorded in recent years, especially in southern Europe and often close to inhabited centers, urges the scientific community to investigate on the impact of these events on air quality and human health at European level as well.

This study examines six large fires (>2000 ha) in Sardinia, Italy, over the past fifteen years, with the main aims to (i) characterize the six forest fires in term of size, fuel, and weather conditions; (ii) estimate the contribution of the six forest fires to environmental PM levels.

Meteorological conditions at synoptic scale have been investigated through NCEP Climate Forecast System Reanalysis (CFSR) data with a spatial resolution of 0.5° x 0.5° and maps of 850 hPa temperature and airmasses from WetterZentrale (https://www.wetterzentrale.de/). The impacts on particulate matter on air quality has been evaluated through data obtained from the monitoring stations of the Air quality control network of the Regional Environment Protection Agency of Sardinia (ARPAS).  To further investigate the impacts of the fire plumes, the study employs the HYSPLIT (hybrid single-particle Lagrangian integrated trajectory) model developed by NOAA’s Air Resources Laboratory to compute the forward trajectories of air masses. Finally, for selected recent fires, the plume spatial distribution has been investigated and verified using Modis satellite images on board the Aqua satellite as well as the visible Infrared Imaging Radiometer Suite (VIIRS) Corrected Reflectance imagery on board the joint NASA/NOAA Suomi National Polar orbiting Partnership (Suomi NPP) satellite.

Preliminary findings reveal varying degrees of correlation between air quality and fire events in the six examined cases. This variability could be attributed to different fuel types, atmospheric conditions, and, to a significant extent, the location and density of air monitoring stations.