Open burning practices in Portugal: links to wildfire occurrence, atmospheric emissions and air quality impacts

Open buring practices (OBPs) of agriculture residues and waste are common practices in Portugal but, when uncontrolled, they can lead to wildfires. The main goals of this study are to describe the temporal and spatial patterns of OBPs and the wildfires they cause, quantify their emissions, and assess the impact of wildfires on air quality during the three-year analyzed period 2020-2022. Statistical analysis tools and numerical algorithms, implemented using high-level programming languages, were employed in order to analyze and describe the temporal and geographical distribution of the phenomena under investigation, as well as characterize their causes. The emission estimations are based on numerical formulas defined in the European Air Pollutant Emission Inventory Guidebook (EEA 2019). WRF-CHIMERE modeling system was adopted to assess the hourly spatial concentration distribution of PM2.5, CO and NO2 in the air during a specific wildfire event. In the three-year analyzed period, the 23% of the wildfires occurred was originated by uncontrolled OBPs. If the analysis is restricted to October-June months, period in which the OBPs occur the most, the OBPs are responsible for 40% of the total wildfires. Considering the annual amount of particulate matter (PM) emissions, OBPs emit more than the Public Electricity and Heat Production (A_PublicPower) and the Road and Rail Transport (F_RoadRail) GNFR sectors, for each year analyzed. The model simulation results show that wildfire events caused by uncontrolled OBPs can have a strong impact on air quality. OBPs are among the main emission sources of the country, and the wildfires they cause may exacerbate air pollution, surpassing the limits set by European legislation and potentially harming human health.